Missing new files in update to xterm 304

4 files changed, 4218 insertions, 0 deletions

diff --git a/app/xterm/graphics_regis.c b/app/xterm/graphics_regis.c
new file mode 100644
index 000000000..be4c10308
--- /dev/null
+++ b/app/xterm/graphics_regis.c
@@ -0,0 +1,3482 @@
+/* $XTermId: graphics_regis.c,v 1.23 2014/05/03 12:44:53 tom Exp $ */
+
+/*
+ * Copyright 2014 by Ross Combs
+ *
+ *                         All Rights Reserved
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the name(s) of the above copyright
+ * holders shall not be used in advertising or otherwise to promote the
+ * sale, use or other dealings in this Software without prior written
+ * authorization.
+ */
+
+#include <xterm.h>
+
+#include <stdio.h>
+#include <ctype.h>
+#include <math.h>
+#include <stdlib.h>
+
+#include <data.h>
+#include <VTparse.h>
+#include <ptyx.h>
+
+#include <assert.h>
+#include <graphics.h>
+#include <graphics_regis.h>
+
+/* get rid of shadowing warnings (we will not draw Bessel functions) */
+#define y1 my_y1
+#define y0 my_y0
+
+#undef DEBUG_BEZIER
+#undef DEBUG_SPLINE_SEGMENTS
+#undef DEBUG_SPLINE_POINTS
+#undef DEBUG_SPLINE_WITH_ROTATION
+#undef DEBUG_SPLINE_WITH_OVERDRAW
+
+#define ITERATIONS_BEFORE_REFRESH 100U
+/* *INDENT-OFF* */
+typedef struct RegisWriteControls {
+    unsigned        pv_multiplier;
+    unsigned        pattern;
+    unsigned        pattern_multiplier;
+    unsigned        invert_pattern;
+    unsigned        plane_mask;
+    unsigned        write_style;
+    RegisterNum     foreground;
+    unsigned        shading_enabled;
+    char            shading_character;
+    int             shading_reference;
+    unsigned        shading_reference_dim;
+} RegisWriteControls;
+
+typedef struct RegisDataFragment {
+    char const     *start;
+    unsigned        pos;
+    unsigned        len;
+} RegisDataFragment;
+
+typedef enum RegisParseLevel {
+    INPUT,
+    OPTIONSET
+} RegisParseLevel;
+/* *INDENT-ON* */
+
+#define CURVE_POSITION_ARC_EDGE     0U
+#define CURVE_POSITION_ARC_CENTER   1U
+#define CURVE_POSITION_OPEN_CURVE   2U
+#define CURVE_POSITION_CLOSED_CURVE 3U
+
+#define MAX_INPUT_CURVE_POINTS 16U
+#define MAX_CURVE_POINTS (MAX_INPUT_CURVE_POINTS + 4U)
+
+typedef struct RegisParseState {
+    RegisDataFragment input;
+    RegisDataFragment optionset;
+    char *temp;
+    unsigned templen;
+    RegisParseLevel level;
+    char command;
+    char option;
+    /* curve options */
+    int curve_mode;
+    int arclen;
+    int x_points[MAX_CURVE_POINTS];
+    int y_points[MAX_CURVE_POINTS];
+    unsigned num_points;
+} RegisParseState;
+
+typedef struct RegisGraphicsContext {
+    Graphic *graphic;
+    int terminal_id;
+    unsigned all_planes;
+    RegisterNum background;
+    RegisWriteControls persistent_write_controls;
+    RegisWriteControls temporary_write_controls;
+    int graphics_output_cursor_x;
+    int graphics_output_cursor_y;
+    unsigned pattern_count;
+    unsigned pattern_bit;
+} RegisGraphicsContext;
+
+#define MAX_PATTERN_BITS 8U
+
+#define WRITE_STYLE_OVERLAY 1U
+#define WRITE_STYLE_REPLACE 2U
+#define WRITE_STYLE_COMPLEMENT 3U
+#define WRITE_STYLE_ERASE 4U
+
+#define WRITE_SHADING_REF_Y 0U
+#define WRITE_SHADING_REF_X 1U
+
+#define ROT_LEFT_N(V, N) ( (((V) << ((N) & 3U )) & 255U) | ((V) >> (8U - ((N) & 3U))) )
+#define ROT_LEFT(V) ( (((V) << 1U) & 255U) | ((V) >> 7U) )
+
+static int
+ifloor(double d)
+{
+    double dl = floor(d);
+    return (int) dl;
+}
+
+static int
+isqrt(double d)
+{
+    double dl = sqrt(d);
+    return (int) dl;
+}
+
+static void
+draw_regis_pixel(RegisGraphicsContext *context, int x, int y)
+{
+    unsigned color = 0;
+
+    switch (context->temporary_write_controls.write_style) {
+    case WRITE_STYLE_OVERLAY:
+	/* update pixels with foreground when pattern is 1, unchanged when pattern is 0 */
+	if (!(context->temporary_write_controls.pattern & context->pattern_bit)) {
+	    return;
+	}
+
+	if (context->temporary_write_controls.invert_pattern) {
+	    color = context->background;
+	} else {
+	    color = context->temporary_write_controls.foreground;
+	}
+	break;
+
+    case WRITE_STYLE_REPLACE:
+	/* update pixels with foreground when pattern is 1, background when pattern is 0 */
+	{
+	    unsigned fg, bg;
+
+	    if (context->temporary_write_controls.invert_pattern) {
+		fg = context->background;
+		bg = context->temporary_write_controls.foreground;
+	    } else {
+		fg = context->temporary_write_controls.foreground;
+		bg = context->background;
+	    }
+	    color = ((context->temporary_write_controls.pattern &
+		      context->pattern_bit)
+		     ? fg
+		     : bg);
+	}
+	break;
+
+    case WRITE_STYLE_COMPLEMENT:
+	/* update pixels with background when pattern is 1, unchanged when pattern is 0 */
+	color = read_pixel(context->graphic, x, y);
+	if (color == COLOR_HOLE)
+	    color = context->background;
+	color = color ^ context->all_planes;
+	break;
+
+    case WRITE_STYLE_ERASE:
+	/* update pixels with foreground */
+	if (context->temporary_write_controls.invert_pattern) {
+	    color = context->temporary_write_controls.foreground;
+	} else {
+	    color = context->background;
+	}
+	break;
+    }
+
+    draw_solid_pixel(context->graphic, x, y, color);
+}
+
+static void
+fill_to_pixel(RegisGraphicsContext *context, int x, int y)
+{
+    unsigned dim = context->temporary_write_controls.shading_reference_dim;
+    int ref = context->temporary_write_controls.shading_reference;
+
+    if (dim == WRITE_SHADING_REF_X) {
+	int delta = x > ref ? 1 : -1;
+	int curr_x;
+
+	context->pattern_bit = 1U << (((unsigned) y) & 7U);
+	for (curr_x = ref; curr_x != x + delta; curr_x += delta) {
+	    draw_regis_pixel(context, curr_x, y);
+	}
+    } else {
+	int delta = y > ref ? 1 : -1;
+	int curr_y;
+
+	for (curr_y = ref; curr_y != y + delta; curr_y += delta) {
+	    context->pattern_bit = 1U << (((unsigned) curr_y) & 7U);
+	    draw_regis_pixel(context, x, curr_y);
+	}
+    }
+}
+
+static void
+draw_patterned_pixel(RegisGraphicsContext *context, int x, int y)
+{
+    if (context->temporary_write_controls.shading_enabled) {
+	if (context->temporary_write_controls.shading_character != '\0') {
+	    /* FIXME: handle character fills */
+	    TRACE(("pixel shaded with character\n"));
+	} else {
+	    fill_to_pixel(context, x, y);
+	}
+    } else {
+	if (context->pattern_count >= context->temporary_write_controls.pattern_multiplier) {
+	    context->pattern_count = 0U;
+	    context->pattern_bit = ROT_LEFT(context->pattern_bit);
+	}
+	context->pattern_count++;
+
+	draw_regis_pixel(context, x, y);
+    }
+}
+
+static void
+draw_patterned_line(RegisGraphicsContext *context, int x1, int y1, int x2, int y2)
+{
+    int x, y;
+    int dx, dy;
+    int dir, diff;
+
+    dx = abs(x1 - x2);
+    dy = abs(y1 - y2);
+
+    if (dx > dy) {
+	if (x1 > x2) {
+	    int tmp;
+	    EXCHANGE(x1, x2, tmp);
+	    EXCHANGE(y1, y2, tmp);
+	}
+	if (y1 < y2)
+	    dir = 1;
+	else if (y1 > y2)
+	    dir = -1;
+	else
+	    dir = 0;
+
+	diff = 0;
+	y = y1;
+	for (x = x1; x <= x2; x++) {
+	    if (diff >= dx) {
+		diff -= dx;
+		y += dir;
+	    }
+	    diff += dy;
+	    draw_patterned_pixel(context, x, y);
+	}
+    } else {
+	if (y1 > y2) {
+	    int tmp;
+	    EXCHANGE(y1, y2, tmp);
+	    EXCHANGE(x1, x2, tmp);
+	}
+	if (x1 < x2)
+	    dir = 1;
+	else if (x1 > x2)
+	    dir = -1;
+	else
+	    dir = 0;
+
+	diff = 0;
+	x = x1;
+	for (y = y1; y <= y2; y++) {
+	    if (diff >= dy) {
+		diff -= dy;
+		x += dir;
+	    }
+	    diff += dx;
+	    draw_patterned_pixel(context, x, y);
+	}
+    }
+}
+
+typedef struct {
+    int dxx;
+    int dxy;
+    int dyx;
+    int dyy;
+} quadmap_coords;
+
+static void
+draw_patterned_arc(RegisGraphicsContext *context,
+		   int cx, int cy,
+		   int ex, int ey,
+		   int a_start, int a_length)
+{
+    const double third = hypot((double) (cx - ex), (double) (cy - ey));
+    const int radius = (int) third;
+    const int ra = radius;
+    const int rb = radius;
+    const quadmap_coords neg_quadmap[4] =
+    {
+	{-1, 0, 0, +1},
+	{0, -1, -1, 0},
+	{+1, 0, 0, -1},
+	{0, +1, +1, 0},
+    };
+    const quadmap_coords pos_quadmap[4] =
+    {
+	{-1, 0, 0, -1},
+	{0, -1, +1, 0},
+	{+1, 0, 0, +1},
+	{0, +1, -1, 0},
+    };
+    const quadmap_coords *quadmap;
+    int total_points;
+    int points_start, points_stop;
+    int points;
+    int iterations;
+    int quad;
+    long rx, ry;
+    long dx, dy;
+    long e2;
+    long error;
+
+    if (a_length == 0)
+	return;
+    if (a_length > 0) {
+	quadmap = pos_quadmap;
+    } else {
+	quadmap = neg_quadmap;
+	if (a_start != 0)
+	    a_start = 360 - a_start;
+    }
+
+    rx = -ra;
+    ry = 0;
+    e2 = rb;
+    dx = (2 * rx + 1) * e2 * e2;
+    dy = rx * rx;
+    error = dx + dy;
+    total_points = 0;
+    do {
+	total_points += 4;
+	e2 = 2 * error;
+	if (e2 >= dx) {
+	    rx++;
+	    dx += 2 * rb * rb;
+	    error += dx;
+	}
+	if (e2 <= dy) {
+	    ry++;
+	    dy += 2 * ra * ra;
+	    error += dy;
+	}
+    }
+    while (rx <= 0);
+    points_start = (total_points * a_start) / 360;
+    points_stop = (total_points * a_start +
+		   total_points * abs(a_length) + 359) / 360;
+    TRACE(("drawing arc with %d points from %d angle for %d degrees (from point %d to %d)\n",
+	   total_points, a_start, a_length, points_start, points_stop));
+
+    points = 0;
+    for (iterations = 0; iterations < 8; iterations++) {
+	quad = iterations & 0x3;
+
+	rx = -ra;
+	ry = 0;
+	e2 = rb;
+	dx = (2 * rx + 1) * e2 * e2;
+	dy = rx * rx;
+	error = dx + dy;
+	do {
+	    if (points >= points_start && points <= points_stop) {
+		draw_patterned_pixel(context,
+				     (int) (cx +
+					    quadmap[quad].dxx * rx +
+					    quadmap[quad].dxy * ry),
+				     (int) (cy +
+					    quadmap[quad].dyx * rx +
+					    quadmap[quad].dyy * ry));
+	    }
+	    points++;
+
+	    e2 = 2 * error;
+	    if (e2 >= dx) {
+		rx++;
+		dx += 2 * rb * rb;
+		error += dx;
+	    }
+	    if (e2 <= dy) {
+		ry++;
+		dy += 2 * ra * ra;
+		error += dy;
+	    }
+	}
+	while (rx <= 0);
+    }
+}
+
+/*
+ * The plot* functions are based on optimized rasterization primitves written by Zingl Alois.
+ * See http://members.chello.at/easyfilter/bresenham.html
+ */
+
+/*
+ * FIXME:
+ * This is a terrible temporary hack.  The plot functions below can be adapted
+ * to work like the other rasterization functions but there's no point in doing
+ * that until we know we don't have to write something completely different.
+ */
+static RegisGraphicsContext *global_context;
+static void
+setPixel(int x, int y)
+{
+    draw_patterned_pixel(global_context, x, y);
+}
+
+static void
+plotLine(int x0, int y0, int x1, int y1)
+{
+    int dx = abs(x1 - x0), sx = x0 < x1 ? 1 : -1;
+    int dy = -abs(y1 - y0), sy = y0 < y1 ? 1 : -1;
+    int err = dx + dy, e2;	/* error value e_xy */
+
+    for (;;) {			/* loop */
+	setPixel(x0, y0);
+	e2 = 2 * err;
+	if (e2 >= dy) {		/* e_xy+e_x > 0 */
+	    if (x0 == x1)
+		break;
+	    err += dy;
+	    x0 += sx;
+	}
+	if (e2 <= dx) {		/* e_xy+e_y < 0 */
+	    if (y0 == y1)
+		break;
+	    err += dx;
+	    y0 += sy;
+	}
+    }
+}
+
+static void
+plotQuadBezierSeg(int x0, int y0, int x1, int y1, int x2, int y2)
+{				/* plot a limited quadratic Bezier segment */
+    int sx = x2 - x1;
+    int sy = y2 - y1;
+    long xx = (x0 - x1);	/* relative values for checks */
+    long yy = (y0 - y1);
+    long xy;
+    double dx, dy, err;
+    double cur = (double) (xx * sy - yy * sx);	/* curvature */
+
+    assert(xx * sx <= 0 && yy * sy <= 0);	/* sign of gradient must not change */
+
+    if (sx * (long) sx + sy * (long) sy > xx * xx + yy * yy) {	/* begin with longer part */
+	x2 = x0;
+	x0 = sx + x1;
+	y2 = y0;
+	y0 = sy + y1;
+	cur = -cur;		/* swap P0 P2 */
+    }
+    if (cur != 0) {		/* no straight line */
+	xx += sx;
+	xx *= sx = x0 < x2 ? 1 : -1;	/* x step direction */
+	yy += sy;
+	yy *= sy = y0 < y2 ? 1 : -1;	/* y step direction */
+	xy = 2 * xx * yy;
+	xx *= xx;
+	yy *= yy;		/* differences 2nd degree */
+	if (cur * sx * sy < 0) {	/* negated curvature? */
+	    xx = -xx;
+	    yy = -yy;
+	    xy = -xy;
+	    cur = -cur;
+	}
+	/* differences 1st degree */
+	dx = ((4.0 * sy * cur * (x1 - x0)) + (double) xx) - (double) xy;
+	dy = ((4.0 * sx * cur * (y0 - y1)) + (double) yy) - (double) xy;
+	xx += xx;
+	yy += yy;
+	err = dx + dy + (double) xy;	/* error 1st step */
+	do {
+	    setPixel(x0, y0);	/* plot curve */
+	    if (x0 == x2 && y0 == y2)
+		return;		/* last pixel -> curve finished */
+	    y1 = (2 * err) < dx;	/* save value for test of y step */
+	    if ((2 * err) > dy) {
+		x0 += sx;
+		dx -= (double) xy;
+		dy += (double) yy;
+		err += dy;
+	    }			/* x step */
+	    if (y1) {
+		y0 += sy;
+		dy -= (double) xy;
+		dx += (double) xx;
+		err += dx;
+	    }			/* y step */
+	} while (dy < 0 && dx > 0);	/* gradient negates -> algorithm fails */
+    }
+    plotLine(x0, y0, x2, y2);	/* plot remaining part to end */
+}
+
+#if 0
+static void
+plotQuadBezier(int x0, int y0, int x1, int y1, int x2, int y2)
+{				/* plot any quadratic Bezier curve */
+    int x = x0 - x1;
+    int y = y0 - y1;
+    double t = x0 - 2 * x1 + x2;
+    double r;
+
+    if ((long) x * (x2 - x1) > 0) {	/* horizontal cut at P4? */
+	if ((long) y * (y2 - y1) > 0)	/* vertical cut at P6 too? */
+	    if (fabs((y0 - 2 * y1 + y2) / t * x) > abs(y)) {	/* which first? */
+		x0 = x2;
+		x2 = x + x1;
+		y0 = y2;
+		y2 = y + y1;	/* swap points */
+	    }			/* now horizontal cut at P4 comes first */
+	t = (x0 - x1) / t;
+	r = (1 - t) * ((1 - t) * y0 + 2.0 * t * y1) + t * t * y2;	/* By(t=P4) */
+	t = (x0 * x2 - x1 * x1) * t / (x0 - x1);	/* gradient dP4/dx=0 */
+	x = ifloor(t + 0.5);
+	y = ifloor(r + 0.5);
+	r = (y1 - y0) * (t - x0) / (x1 - x0) + y0;	/* intersect P3 | P0 P1 */
+	plotQuadBezierSeg(x0, y0, x, ifloor(r + 0.5), x, y);
+	r = (y1 - y2) * (t - x2) / (x1 - x2) + y2;	/* intersect P4 | P1 P2 */
+	x0 = x1 = x;
+	y0 = y;
+	y1 = ifloor(r + 0.5);	/* P0 = P4, P1 = P8 */
+    }
+    if ((long) (y0 - y1) * (y2 - y1) > 0) {	/* vertical cut at P6? */
+	t = y0 - 2 * y1 + y2;
+	t = (y0 - y1) / t;
+	r = (1 - t) * ((1 - t) * x0 + 2.0 * t * x1) + t * t * x2;	/* Bx(t=P6) */
+	t = (y0 * y2 - y1 * y1) * t / (y0 - y1);	/* gradient dP6/dy=0 */
+	x = ifloor(r + 0.5);
+	y = ifloor(t + 0.5);
+	r = (x1 - x0) * (t - y0) / (y1 - y0) + x0;	/* intersect P6 | P0 P1 */
+	plotQuadBezierSeg(x0, y0, ifloor(r + 0.5), y, x, y);
+	r = (x1 - x2) * (t - y2) / (y1 - y2) + x2;	/* intersect P7 | P1 P2 */
+	x0 = x;
+	x1 = ifloor(r + 0.5);
+	y0 = y1 = y;		/* P0 = P6, P1 = P7 */
+    }
+    plotQuadBezierSeg(x0, y0, x1, y1, x2, y2);	/* remaining part */
+}
+#endif
+
+static void
+plotCubicBezierSeg(int x0, int y0,
+		   double x1, double y1,
+		   double x2, double y2,
+		   int x3, int y3)
+{				/* plot limited cubic Bezier segment */
+    int f, fx, fy, tt;
+    int leg = 1;
+    int sx = x0 < x3 ? 1 : -1;
+    int sy = y0 < y3 ? 1 : -1;	/* step direction */
+    double xc = -fabs(x0 + x1 - x2 - x3);
+    double xa = xc - 4 * sx * (x1 - x2);
+    double xb = sx * (x0 - x1 - x2 + x3);
+    double yc = -fabs(y0 + y1 - y2 - y3);
+    double ya = yc - 4 * sy * (y1 - y2);
+    double yb = sy * (y0 - y1 - y2 + y3);
+    double ab, ac, bc, cb, xx, xy, yy, dx, dy, ex, *pxy;
+    double EP = 0.01;
+    /* check for curve restrains */
+    /* slope P0-P1 == P2-P3    and  (P0-P3 == P1-P2      or   no slope change) */
+    assert((x1 - x0) * (x2 - x3) < EP &&
+	   ((x3 - x0) * (x1 - x2) < EP || xb * xb < xa * xc + EP));
+    assert((y1 - y0) * (y2 - y3) < EP &&
+	   ((y3 - y0) * (y1 - y2) < EP || yb * yb < ya * yc + EP));
+
+    if (xa == 0 && ya == 0) {	/* quadratic Bezier */
+	sx = ifloor((3 * x1 - x0 + 1) / 2);
+	sy = ifloor((3 * y1 - y0 + 1) / 2);	/* new midpoint */
+	plotQuadBezierSeg(x0, y0, sx, sy, x3, y3);
+	return;
+    }
+    x1 = (x1 - x0) * (x1 - x0) + (y1 - y0) * (y1 - y0) + 1;	/* line lengths */
+    x2 = (x2 - x3) * (x2 - x3) + (y2 - y3) * (y2 - y3) + 1;
+    do {			/* loop over both ends */
+	ab = xa * yb - xb * ya;
+	ac = xa * yc - xc * ya;
+	bc = xb * yc - xc * yb;
+	ex = ab * (ab + ac - 3 * bc) + ac * ac;		/* P0 part of self-intersection loop? */
+	f = ((ex > 0.0)
+	     ? 1
+	     : isqrt(1 + 1024 / x1));	/* calculate resolution */
+	ab *= f;
+	ac *= f;
+	bc *= f;
+	ex *= f * f;		/* increase resolution */
+	xy = 9 * (ab + ac + bc) / 8;
+	cb = 8 * (xa - ya);	/* init differences of 1st degree */
+	dx = 27 * (8 * ab * (yb * yb - ya * yc) +
+		   ex * (ya + 2 * yb + yc)) / 64 - ya * ya * (xy - ya);
+	dy = 27 * (8 * ab * (xb * xb - xa * xc) -
+		   ex * (xa + 2 * xb + xc)) / 64 - xa * xa * (xy + xa);
+	/* init differences of 2nd degree */
+	xx = 3 * (3 * ab * (3 * yb * yb - ya * ya - 2 * ya * yc) -
+		  ya * (3 * ac * (ya + yb) + ya * cb)) / 4;
+	yy = 3 * (3 * ab * (3 * xb * xb - xa * xa - 2 * xa * xc) -
+		  xa * (3 * ac * (xa + xb) + xa * cb)) / 4;
+	xy = xa * ya * (6 * ab + 6 * ac - 3 * bc + cb);
+	ac = ya * ya;
+	cb = xa * xa;
+	xy = 3 * (xy + 9 * f * (cb * yb * yc - xb * xc * ac) -
+		  18 * xb * yb * ab) / 8;
+
+	if (ex < 0) {		/* negate values if inside self-intersection loop */
+	    dx = -dx;
+	    dy = -dy;
+	    xx = -xx;
+	    yy = -yy;
+	    xy = -xy;
+	    ac = -ac;
+	    cb = -cb;
+	}			/* init differences of 3rd degree */
+	ab = 6 * ya * ac;
+	ac = -6 * xa * ac;
+	bc = 6 * ya * cb;
+	cb = -6 * xa * cb;
+	dx += xy;
+	ex = dx + dy;
+	dy += xy;		/* error of 1st step */
+
+	for (pxy = &xy, fx = fy = f; x0 != x3 && y0 != y3;) {
+	    setPixel(x0, y0);	/* plot curve */
+	    do {		/* move sub-steps of one pixel */
+		if (dx > *pxy || dy < *pxy)
+		    goto exit;	/* confusing values */
+		y1 = 2 * ex - dy;	/* save value for test of y step */
+		if (2 * ex >= dx) {	/* x sub-step */
+		    fx--;
+		    ex += dx += xx;
+		    dy += xy += ac;
+		    yy += bc;
+		    xx += ab;
+		}
+		if (y1 <= 0) {	/* y sub-step */
+		    fy--;
+		    ex += dy += yy;
+		    dx += xy += bc;
+		    xx += ac;
+		    yy += cb;
+		}
+	    } while (fx > 0 && fy > 0);		/* pixel complete? */
+	    if (2 * fx <= f) {
+		x0 += sx;
+		fx += f;
+	    }			/* x step */
+	    if (2 * fy <= f) {
+		y0 += sy;
+		fy += f;
+	    }			/* y step */
+	    if (pxy == &xy && dx < 0 && dy > 0)
+		pxy = &EP;	/* pixel ahead valid */
+	}
+      exit:
+	EXCHANGE(x0, x3, tt);
+	sx = -sx;
+	xb = -xb;		/* swap legs */
+	EXCHANGE(y0, y3, tt);
+	sy = -sy;
+	yb = -yb;
+	x1 = x2;
+    } while (leg--);		/* try other end */
+    plotLine(x0, y0, x3, y3);	/* remaining part in case of cusp or crunode */
+}
+
+static void
+plotCubicBezier(int x0, int y0, int x1, int y1,
+		int x2, int y2, int x3, int y3)
+{				/* plot any cubic Bezier curve */
+    int n = 0, i = 0;
+    long xc = x0 + x1 - x2 - x3;
+    long xa = xc - 4 * (x1 - x2);
+    long xb = x0 - x1 - x2 + x3;
+    long xd = xb + 4 * (x1 + x2);
+    long yc = y0 + y1 - y2 - y3;
+    long ya = yc - 4 * (y1 - y2);
+    long yb = y0 - y1 - y2 + y3;
+    long yd = yb + 4 * (y1 + y2);
+    double fx0 = x0, fx1, fx2, fx3, fy0 = y0, fy1, fy2, fy3;
+    double t1 = (double) (xb * xb - xa * xc), t2, t[5];
+
+#ifdef DEBUG_BEZIER
+    printf("plotCubicBezier(%d,%d, %d,%d, %d,%d, %d,%d\n",
+	   x0, y0, x1, y1, x2, y2, x3, y3);
+#endif
+    /* sub-divide curve at gradient sign changes */
+    if (xa == 0) {		/* horizontal */
+	if (labs(xc) < 2 * labs(xb))
+	    t[n++] = (double) xc / (2.0 * (double) xb);		/* one change */
+    } else if (t1 > 0.0) {	/* two changes */
+	t2 = sqrt(t1);
+	t1 = ((double) xb - t2) / (double) xa;
+	if (fabs(t1) < 1.0)
+	    t[n++] = t1;
+	t1 = ((double) xb + t2) / (double) xa;
+	if (fabs(t1) < 1.0)
+	    t[n++] = t1;
+    }
+    t1 = (double) (yb * yb - ya * yc);
+    if (ya == 0) {		/* vertical */
+	if (labs(yc) < 2 * labs(yb))
+	    t[n++] = (double) yc / (2.0 * (double) yb);		/* one change */
+    } else if (t1 > 0.0) {	/* two changes */
+	t2 = sqrt(t1);
+	t1 = ((double) yb - t2) / (double) ya;
+	if (fabs(t1) < 1.0)
+	    t[n++] = t1;
+	t1 = ((double) yb + t2) / (double) ya;
+	if (fabs(t1) < 1.0)
+	    t[n++] = t1;
+    }
+    for (i = 1; i < n; i++)	/* bubble sort of 4 points */
+	if ((t1 = t[i - 1]) > t[i]) {
+	    t[i - 1] = t[i];
+	    t[i] = t1;
+	    i = 0;
+	}
+
+    t1 = -1.0;
+    t[n] = 1.0;			/* begin / end point */
+    for (i = 0; i <= n; i++) {	/* plot each segment separately */
+	t2 = t[i];		/* sub-divide at t[i-1], t[i] */
+	fx1 = (t1 * (t1 * (double) xb - (double) (2 * xc)) -
+	       t2 * (t1 * (t1 * (double) xa - (double) (2 * xb)) + (double)
+		     xc) + (double) xd) / 8 - fx0;
+	fy1 = (t1 * (t1 * (double) yb - (double) (2 * yc)) -
+	       t2 * (t1 * (t1 * (double) ya - (double) (2 * yb)) + (double)
+		     yc) + (double) yd) / 8 - fy0;
+	fx2 = (t2 * (t2 * (double) xb - (double) (2 * xc)) -
+	       t1 * (t2 * (t2 * (double) xa - (double) (2 * xb)) + (double)
+		     xc) + (double) xd) / 8 - fx0;
+	fy2 = (t2 * (t2 * (double) yb - (double) (2 * yc)) -
+	       t1 * (t2 * (t2 * (double) ya - (double) (2 * yb)) + (double)
+		     yc) + (double) yd) / 8 - fy0;
+	fx0 -= fx3 = (t2 * (t2 * ((double) (3 * xb) - t2 * (double) xa) -
+			    (double) (3 * xc)) + (double) xd) / 8;
+	fy0 -= fy3 = (t2 * (t2 * ((double) (3 * yb) - t2 * (double) ya) -
+			    (double) (3 * yc)) + (double) yd) / 8;
+	x3 = ifloor(fx3 + 0.5);
+	y3 = ifloor(fy3 + 0.5);	/* scale bounds to int */
+	if (fx0 != 0.0) {
+	    fx1 *= fx0 = (x0 - x3) / fx0;
+	    fx2 *= fx0;
+	}
+	if (fy0 != 0.0) {
+	    fy1 *= fy0 = (y0 - y3) / fy0;
+	    fy2 *= fy0;
+	}
+	if (x0 != x3 || y0 != y3)	/* segment t1 - t2 */
+	    plotCubicBezierSeg(x0, y0,
+			       x0 + fx1, y0 + fy1,
+			       x0 + fx2, y0 + fy2,
+			       x3, y3);
+	x0 = x3;
+	y0 = y3;
+	fx0 = fx3;
+	fy0 = fy3;
+	t1 = t2;
+    }
+}
+
+#if 0
+static void
+plotQuadSpline(int n, int x[], int y[], int skip_segments)
+{				/* plot quadratic spline, destroys input arrays x,y */
+#define M_MAX 12
+    double mi = 1, m[M_MAX];	/* diagonal constants of matrix */
+    int i, x0, y0, x1, y1, x2, y2;
+#ifdef DEBUG_SPLINE_SEGMENTS
+    int color = 0;
+#endif
+
+    assert(n > 1);		/* need at least 3 points P[0]..P[n] */
+
+#ifdef DEBUG_SPLINE_POINTS
+    {
+	int save_pattern;
+
+	i = 0;
+	global_context->temporary_write_controls.foreground = 11;
+	save_pattern = global_context->temporary_write_controls.pattern;
+	global_context->temporary_write_controls.pattern = 0xff;
+	draw_patterned_arc(global_context, x[i], y[i], x[i] + 2, y[i], 0, 360);
+	i++;
+	global_context->temporary_write_controls.foreground = 15;
+	for (; i < n; i++) {
+	    draw_patterned_arc(global_context,
+			       x[i], y[i],
+			       x[i] + 2, y[i],
+			       0, 360);
+	}
+	global_context->temporary_write_controls.foreground = 10;
+	draw_patterned_arc(global_context, x[i], y[n], x[i] + 2, y[i], 0, 360);
+	global_context->temporary_write_controls.pattern = save_pattern;
+    }
+#endif
+
+    x2 = x[n];
+    y2 = y[n];
+
+    x[1] = x0 = 8 * x[1] - 2 * x[0];	/* first row of matrix */
+    y[1] = y0 = 8 * y[1] - 2 * y[0];
+
+    for (i = 2; i < n; i++) {	/* forward sweep */
+	if (i - 2 < M_MAX)
+	    m[i - 2] = mi = 1.0 / (6.0 - mi);
+	x[i] = x0 = ifloor(8 * x[i] - x0 * mi + 0.5);	/* store yi */
+	y[i] = y0 = ifloor(8 * y[i] - y0 * mi + 0.5);
+    }
+    x1 = ifloor((x0 - 2 * x2) / (5.0 - mi) + 0.5);	/* correction last row */
+    y1 = ifloor((y0 - 2 * y2) / (5.0 - mi) + 0.5);
+
+    for (i = n - 2; i > 0; i--) {	/* back substitution */
+	if (i <= M_MAX)
+	    mi = m[i - 1];
+	x0 = ifloor((x[i] - x1) * mi + 0.5);	/* next corner */
+	y0 = ifloor((y[i] - y1) * mi + 0.5);
+#ifdef DEBUG_SPLINE_SEGMENTS
+	color++;
+	global_context->temporary_write_controls.foreground = color;
+#endif
+	if ((n - 2) - i < skip_segments)
+	    plotQuadBezier((x0 + x1) / 2, (y0 + y1) / 2, x1, y1, x2, y2);
+	x2 = (x0 + x1) / 2;
+	x1 = x0;
+	y2 = (y0 + y1) / 2;
+	y1 = y0;
+    }
+#ifdef DEBUG_SPLINE_SEGMENTS
+    color++;
+    global_context->temporary_write_controls.foreground = color;
+#endif
+    if (skip_segments > 0)
+	plotQuadBezier(x[0], y[0], x1, y1, x2, y2);
+}
+#endif
+
+static void
+plotCubicSpline(int n, int x[], int y[], int skip_first_last)
+{
+#define M_MAX 12
+    double mi = 0.25, m[M_MAX];	/* diagonal constants of matrix */
+    int x3, y3, x4, y4;
+    int i, x0, y0, x1, y1, x2, y2;
+#ifdef DEBUG_SPLINE_SEGMENTS
+    int color = 0;
+#endif
+
+    assert(n > 2);		/* need at least 4 points P[0]..P[n] */
+
+#ifdef DEBUG_SPLINE_POINTS
+    {
+	int save_pattern;
+
+	i = 0;
+	global_context->temporary_write_controls.foreground = 11;
+	save_pattern = global_context->temporary_write_controls.pattern;
+	global_context->temporary_write_controls.pattern = 0xff;
+	draw_patterned_arc(global_context, x[i], y[i], x[i] + 2, y[i], 0, 360);
+	i++;
+	global_context->temporary_write_controls.foreground = 15;
+	for (; i < n; i++) {
+	    draw_patterned_arc(global_context,
+			       x[i], y[i],
+			       x[i] + 2, y[i],
+			       0, 360);
+	}
+	global_context->temporary_write_controls.foreground = 10;
+	draw_patterned_arc(global_context, x[i], y[i], x[i] + 2, y[i], 0, 360);
+	global_context->temporary_write_controls.pattern = save_pattern;
+    }
+#endif
+
+    x3 = x[n - 1];
+    y3 = y[n - 1];
+    x4 = x[n];
+    y4 = y[n];
+
+    x[1] = x0 = 12 * x[1] - 3 * x[0];	/* first row of matrix */
+    y[1] = y0 = 12 * y[1] - 3 * y[0];
+
+    for (i = 2; i < n; i++) {	/* forward sweep */
+	if (i - 2 < M_MAX)
+	    m[i - 2] = mi = 0.25 / (2.0 - mi);
+	x[i] = x0 = ifloor(12 * x[i] - 2 * x0 * mi + 0.5);
+	y[i] = y0 = ifloor(12 * y[i] - 2 * y0 * mi + 0.5);
+    }
+    x2 = ifloor((x0 - 3 * x4) / (7 - 4 * mi) + 0.5);	/* correct last row */
+    printf("y0=%d, y4=%d mi=%g\n", y0, y4, mi);
+    y2 = ifloor((y0 - 3 * y4) / (7 - 4 * mi) + 0.5);
+    printf("y2=%d, y3=%d, y4=%d\n", y2, y3, y4);
+#ifdef DEBUG_SPLINE_SEGMENTS
+    color++;
+    global_context->temporary_write_controls.foreground = color;
+#endif
+    if (!skip_first_last)
+	plotCubicBezier(x3, y3, (x2 + x4) / 2, (y2 + y4) / 2, x4, y4, x4, y4);
+
+    if (n - 3 < M_MAX)
+	mi = m[n - 3];
+    x1 = ifloor((x[n - 2] - 2 * x2) * mi + 0.5);
+    y1 = ifloor((y[n - 2] - 2 * y2) * mi + 0.5);
+    for (i = n - 3; i > 0; i--) {	/* back substitution */
+	if (i <= M_MAX)
+	    mi = m[i - 1];
+	x0 = ifloor((x[i] - 2 * x1) * mi + 0.5);
+	y0 = ifloor((y[i] - 2 * y1) * mi + 0.5);
+	x4 = ifloor((x0 + 4 * x1 + x2 + 3) / 6.0);	/* reconstruct P[i] */
+	y4 = ifloor((y0 + 4 * y1 + y2 + 3) / 6.0);
+#ifdef DEBUG_SPLINE_SEGMENTS
+	color++;
+	global_context->temporary_write_controls.foreground = color;
+#endif
+	plotCubicBezier(x4, y4,
+			ifloor((2 * x1 + x2) / 3 + 0.5),
+			ifloor((2 * y1 + y2) / 3 + 0.5),
+			ifloor((x1 + 2 * x2) / 3 + 0.5),
+			ifloor((y1 + 2 * y2) / 3 + 0.5),
+			x3, y3);
+	x3 = x4;
+	y3 = y4;
+	x2 = x1;
+	y2 = y1;
+	x1 = x0;
+	y1 = y0;
+    }
+    x0 = x[0];
+    x4 = ifloor((3 * x0 + 7 * x1 + 2 * x2 + 6) / 12.0);		/* reconstruct P[1] */
+    y0 = y[0];
+    y4 = ifloor((3 * y0 + 7 * y1 + 2 * y2 + 6) / 12.0);
+#ifdef DEBUG_SPLINE_SEGMENTS
+    global_context->temporary_write_controls.foreground = 4;
+#endif
+    plotCubicBezier(x4, y4,
+		    ifloor((2 * x1 + x2) / 3 + 0.5),
+		    ifloor((2 * y1 + y2) / 3 + 0.5),
+		    ifloor((x1 + 2 * x2) / 3 + 0.5),
+		    ifloor((y1 + 2 * y2) / 3 + 0.5),
+		    x3, y3);
+#ifdef DEBUG_SPLINE_SEGMENTS
+    color++;
+    global_context->temporary_write_controls.foreground = color;
+#endif
+    if (!skip_first_last)
+	plotCubicBezier(x0, y0, x0, y0, (x0 + x1) / 2, (y0 + y1) / 2, x4, y4);
+}
+
+static void
+init_fragment(RegisDataFragment *fragment, char const *str)
+{
+    fragment->start = str;
+    fragment->len = (unsigned) strlen(str);
+    fragment->pos = 0U;
+}
+
+static void
+copy_fragment(RegisDataFragment *dst, RegisDataFragment const *src)
+{
+    dst->start = src->start;
+    dst->len = src->len;
+    dst->pos = src->pos;
+}
+
+static char
+peek_fragment(RegisDataFragment const *fragment)
+{
+    if (fragment->pos < fragment->len) {
+	return fragment->start[fragment->pos];
+    }
+    return '\0';
+}
+
+static char
+pop_fragment(RegisDataFragment *fragment)
+{
+    if (fragment->pos < fragment->len) {
+	return fragment->start[fragment->pos++];
+    }
+    return '\0';
+}
+
+static size_t
+fragment_len(RegisDataFragment const *fragment)
+{
+    return fragment->len - fragment->pos;
+}
+
+#define MAX_FRAG 1024
+static char const *
+fragment_to_tempstr(RegisDataFragment const *fragment)
+{
+    static char tempstr[MAX_FRAG + 1];
+    size_t remaininglen = fragment_len(fragment);
+    size_t minlen = ((remaininglen < MAX_FRAG)
+		     ? remaininglen
+		     : MAX_FRAG);
+
+    (void) strncpy(tempstr, &fragment->start[fragment->pos], minlen);
+    tempstr[minlen] = '\0';
+    return tempstr;
+}
+
+static int
+skip_regis_whitespace(RegisDataFragment *input)
+{
+    int skipped = 0;
+    char ch;
+
+    assert(input);
+
+    for (; input->pos < input->len; input->pos++) {
+	/* FIXME: the semicolon isn't whitespace -- it also terminates the current command even if inside of an optionset or extent */
+	ch = input->start[input->pos];
+	if (ch != ',' && ch != ';' && !IsSpace(ch)) {
+	    break;
+	}
+	if (ch == '\n') {
+	    TRACE(("end of input line\n\n"));
+	}
+	skipped = 1;
+    }
+
+    if (skipped)
+	return 1;
+    return 0;
+}
+
+static int
+extract_regis_extent(RegisDataFragment *input, RegisDataFragment *output)
+{
+    char ch;
+
+    assert(input);
+    assert(output);
+
+    output->start = &input->start[input->pos];
+    output->len = 0U;
+    output->pos = 0U;
+
+    if (input->pos >= input->len)
+	return 0;
+
+    ch = input->start[input->pos];
+    if (ch != '[')
+	return 0;
+    input->pos++;
+    output->start++;
+
+    /* FIXME: truncate to 16 bit signed integers */
+    for (; input->pos < input->len; input->pos++, output->len++) {
+	ch = input->start[input->pos];
+	if (ch == ';') {
+	    TRACE(("DATA_ERROR: end of input before closing bracket\n"));
+	    break;
+	}
+	if (ch == ']')
+	    break;
+    }
+    if (ch == ']')
+	input->pos++;
+
+    return 1;
+}
+
+static int
+extract_regis_num(RegisDataFragment *input, RegisDataFragment *output)
+{
+    char ch = 0;
+    int has_digits = 0;
+
+    assert(input);
+    assert(output);
+
+    output->start = &input->start[input->pos];
+    output->len = 0U;
+    output->pos = 0U;
+
+    for (; input->pos < input->len; input->pos++, output->len++) {
+	ch = input->start[input->pos];
+	if (ch != '0' && ch != '1' && ch != '2' && ch != '3' &&
+	    ch != '4' && ch != '5' && ch != '6' && ch != '7' &&
+	    ch != '8' && ch != '9') {
+	    break;
+	}
+	has_digits = 1;
+    }
+
+    /* FIXME: what degenerate forms should be accepted ("E10" "1E" "1e" "1." "1ee10")? */
+    /* FIXME: the terminal is said to support "floating point values", truncating to int... what do these look like? */
+    if (has_digits && ch == 'E') {
+	input->pos++;
+	output->len++;
+	for (; input->pos < input->len; input->pos++, output->len++) {
+	    ch = input->start[input->pos];
+	    if (ch != '0' && ch != '1' && ch != '2' && ch != '3' &&
+		ch != '4' && ch != '5' && ch != '6' && ch != '7' &&
+		ch != '8' && ch != '9') {
+		break;
+	    }
+	}
+    }
+
+    if (output->len < 1U)
+	return 0;
+
+    return 1;
+}
+
+static int
+extract_regis_pixelvector(RegisDataFragment *input, RegisDataFragment *output)
+{
+    char ch;
+    int has_digits;
+
+    assert(input);
+    assert(output);
+
+    output->start = &input->start[input->pos];
+    output->len = 0U;
+    output->pos = 0U;
+
+    if (input->pos < input->len) {
+	ch = input->start[input->pos];
+	if (ch == '+' || ch == '-') {
+	    input->pos++;
+	    output->len++;
+	}
+    }
+
+    has_digits = 0;
+    for (; input->pos < input->len; input->pos++, output->len++) {
+	ch = input->start[input->pos];
+	if (ch != '0' && ch != '1' && ch != '2' && ch != '3' &&
+	    ch != '4' && ch != '5' && ch != '6' && ch != '7') {
+	    break;
+	}
+	has_digits = 1;
+    }
+
+    return has_digits;
+}
+
+static int
+extract_regis_command(RegisDataFragment *input, char *command)
+{
+    char ch;
+
+    assert(input);
+    assert(command);
+
+    if (input->pos >= input->len)
+	return 0;
+
+    ch = input->start[input->pos];
+    if (ch == '\0' || ch == ';') {
+	return 0;
+    }
+    if (!islower(ch) && !isupper(ch)) {
+	return 0;
+    }
+    *command = ch;
+    input->pos++;
+
+    return 1;
+}
+
+static int
+extract_regis_string(RegisDataFragment *input, char *out, unsigned maxlen)
+{
+    char first_ch;
+    char ch;
+    char prev_ch;
+    unsigned outlen = 0U;
+
+    assert(input);
+    assert(out);
+
+    if (input->pos >= input->len)
+	return 0;
+
+    ch = input->start[input->pos];
+    if (ch != '\'' && ch != '"')
+	return 0;
+    first_ch = ch;
+    input->pos++;
+
+    ch = '\0';
+    for (; input->pos < input->len; input->pos++) {
+	prev_ch = ch;
+	ch = input->start[input->pos];
+	/* ';' (resync) is not recognized in strings */
+	if (prev_ch == first_ch) {
+	    if (ch == first_ch) {
+		if (outlen < maxlen) {
+		    out[outlen] = ch;
+		}
+		outlen++;
+		ch = '\0';
+		continue;
+	    }
+	    if (outlen < maxlen)
+		out[outlen] = '\0';
+	    else
+		out[maxlen] = '\0';
+	    return 1;
+	}
+	if (ch == '\0')
+	    break;
+	if (ch != first_ch) {
+	    if (outlen < maxlen) {
+		out[outlen] = ch;
+	    }
+	    outlen++;
+	}
+    }
+    if (ch == first_ch) {
+	if (outlen < maxlen)
+	    out[outlen] = '\0';
+	else
+	    out[maxlen] = '\0';
+	return 1;
+    }
+    /* FIXME: handle multiple strings concatenated with commas */
+
+    TRACE(("DATA_ERROR: end of input during before closing quote\n"));
+    return 0;
+}
+
+static int
+extract_regis_optionset(RegisDataFragment *input, RegisDataFragment *output)
+{
+    char ch;
+    int nesting;
+
+    assert(input);
+    assert(output);
+
+    output->start = &input->start[input->pos];
+    output->len = 0U;
+    output->pos = 0U;
+
+    if (input->pos >= input->len)
+	return 0;
+
+    ch = input->start[input->pos];
+    if (ch != '(')
+	return 0;
+    input->pos++;
+    output->start++;
+    nesting = 1;
+
+    /* FIXME: handle strings with parens */
+    for (; input->pos < input->len; input->pos++, output->len++) {
+	ch = input->start[input->pos];
+	if (ch == ';')
+	    break;
+	if (ch == '(')
+	    nesting++;
+	if (ch == ')') {
+	    nesting--;
+	    if (nesting == 0) {
+		input->pos++;
+		return 1;
+	    }
+	}
+    }
+
+    TRACE(("DATA_ERROR: end of input before closing paren (%d levels deep)\n", nesting));
+    return 0;
+}
+
+static int
+extract_regis_option(RegisDataFragment *input,
+		     char *option,
+		     RegisDataFragment *output)
+{
+    char ch;
+    int nesting;
+
+    assert(input);
+    assert(option);
+    assert(output);
+
+    /* LETTER suboptions* value? */
+    /* FIXME: can there be whitespace or commas inside of an option? */
+    /* FIXME: what are the rules for using separate parens vs. sharing between options? */
+
+    output->start = &input->start[input->pos];
+    output->len = 0U;
+    output->pos = 0U;
+
+    if (input->pos >= input->len) {
+	return 0;
+    }
+
+    ch = input->start[input->pos];
+    if (ch == ';' || ch == ',' || ch == '(' || ch == ')' || isdigit(ch)) {
+	return 0;
+    }
+    *option = ch;
+    input->pos++;
+    output->start++;
+    nesting = 0;
+
+    /* FIXME: handle strings with parens, nested parens, etc. */
+    for (; input->pos < input->len; input->pos++, output->len++) {
+	ch = input->start[input->pos];
+	TRACE(("looking at option char %c\n", ch));
+	/* FIXME: any special rules for commas?  any need to track parens? */
+	if (ch == '(') {
+	    TRACE(("nesting++\n"));
+	    nesting++;
+	}
+	if (ch == ')') {
+	    TRACE(("nesting--\n"));
+	    nesting--;
+	    if (nesting < 0) {
+		TRACE(("DATA_ERROR: found ReGIS option has value with too many close parens \"%c\"\n", *option));
+		return 0;
+	    }
+	}
+	/* top-level commas indicate the end of this option and the start of another */
+	if (nesting == 0 && ch == ',')
+	    break;
+	if (ch == ';')
+	    break;
+    }
+    if (nesting != 0) {
+	TRACE(("DATA_ERROR: mismatched parens in argument to ReGIS option \"%c\"\n", *option));
+	return 0;
+    }
+
+    TRACE(("found ReGIS option and value \"%c\" \"%s\"\n",
+	   *option,
+	   fragment_to_tempstr(output)));
+    return 1;
+}
+
+static int
+regis_num_to_int(RegisDataFragment const *input, int *out)
+{
+    char ch;
+
+    /* FIXME: handle exponential notation and rounding */
+    /* FIXME: check for junk after the number */
+    ch = peek_fragment(input);
+    if (ch != '0' &&
+	ch != '1' &&
+	ch != '2' &&
+	ch != '3' &&
+	ch != '4' &&
+	ch != '5' &&
+	ch != '6' &&
+	ch != '7' &&
+	ch != '8' &&
+	ch != '9' &&
+	ch != '+' &&
+	ch != '-') {
+	return 0;
+    }
+
+    TRACE(("converting \"%s\" to an int\n", fragment_to_tempstr(input)));
+    *out = atoi(fragment_to_tempstr(input));
+    return 1;
+}
+
+static int
+load_regis_colorspec(Graphic const *graphic, RegisDataFragment const *input, RegisterNum *out)
+{
+    int val;
+    RegisDataFragment colorspec;
+    RegisDataFragment coloroption;
+
+    copy_fragment(&colorspec, input);
+    TRACE(("looking at colorspec pattern: \"%s\"\n", fragment_to_tempstr(&colorspec)));
+
+    if (regis_num_to_int(&colorspec, &val)) {
+	if (val < 0 || val >= (int) graphic->valid_registers) {		/* FIXME: wrap? */
+	    TRACE(("DATA_ERROR: colorspec value %d\n", val));
+	    return 0;
+	}
+	TRACE(("colorspec contains index for register %u\n", val));
+	*out = (RegisterNum) val;
+	return 1;
+    }
+
+    if (extract_regis_optionset(&colorspec, &coloroption)) {
+	short r, g, b;
+	TRACE(("option: \"%s\"\n", fragment_to_tempstr(&coloroption)));
+
+	if (fragment_len(&coloroption) == 1) {
+	    char ch = pop_fragment(&coloroption);
+
+	    TRACE(("got regis RGB colorspec pattern: \"%s\"\n",
+		   fragment_to_tempstr(&coloroption)));
+	    switch (ch) {
+	    case 'D':
+	    case 'd':
+		r = 0;
+		g = 0;
+		b = 0;
+		break;
+	    case 'R':
+	    case 'r':
+		r = 100;
+		g = 0;
+		b = 0;
+		break;
+	    case 'G':
+	    case 'g':
+		r = 0;
+		g = 100;
+		b = 0;
+		break;
+	    case 'B':
+	    case 'b':
+		r = 0;
+		g = 0;
+		b = 100;
+		break;
+	    case 'C':
+	    case 'c':
+		r = 0;
+		g = 100;
+		b = 100;
+		break;
+	    case 'Y':
+	    case 'y':
+		r = 100;
+		g = 100;
+		b = 0;
+		break;
+	    case 'M':
+	    case 'm':
+		r = 100;
+		g = 0;
+		b = 100;
+		break;
+	    case 'W':
+	    case 'w':
+		r = 100;
+		g = 100;
+		b = 100;
+		break;
+	    default:
+		TRACE(("unknown RGB color name: \"%c\"\n", ch));
+		return 0;
+	    }
+	} else {
+	    short h, l, s;
+
+	    if (sscanf(fragment_to_tempstr(&coloroption),
+		       "%*1[Hh]%hd%*1[Ll]%hd%*1[Ss]%hd",
+		       &h, &l, &s) != 3) {
+		TRACE(("unrecognized colorspec format: \"%s\"\n",
+		       fragment_to_tempstr(&coloroption)));
+		return 0;
+	    }
+	    hls2rgb(h, l, s, &r, &g, &b);
+	}
+	/* FIXME: check for trailing junk? */
+	*out = find_color_register(graphic->color_registers, r, g, b);
+	TRACE(("colorspec maps to closest register %u\n", *out));
+	return 1;
+    }
+
+    TRACE(("unrecognized colorspec format: \"%s\"\n", fragment_to_tempstr(&colorspec)));
+    return 0;
+}
+
+static int
+load_regis_extent(char const *extent, int origx, int origy, int *xloc, int *yloc)
+{
+    int xsign, ysign;
+    char const *xpart;
+    char const *ypart;
+
+    xpart = extent;
+    if ((ypart = strchr(extent, ','))) {
+	ypart++;
+    } else {
+	ypart = "";
+    }
+
+    if (xpart[0] == '-') {
+	xsign = -1;
+	xpart++;
+    } else if (xpart[0] == '+') {
+	xsign = +1;
+	xpart++;
+    } else {
+	xsign = 0;
+    }
+    if (ypart[0] == '-') {
+	ysign = -1;
+	ypart++;
+    } else if (ypart[0] == '+') {
+	ysign = +1;
+	ypart++;
+    } else {
+	ysign = 0;
+    }
+
+    if (xpart[0] == '\0' || xpart[0] == ',') {
+	*xloc = origx;
+    } else if (xsign == 0) {
+	*xloc = atoi(xpart);
+    } else {
+	*xloc = origx + xsign * atoi(xpart);
+    }
+    if (ypart[0] == '\0') {
+	*yloc = origy;
+    } else if (ysign == 0) {
+	*yloc = atoi(ypart);
+    } else {
+	*yloc = origy + ysign * atoi(ypart);
+    }
+
+    return 1;
+}
+
+static int
+load_regis_pixelvector(char const *pixelvector,
+		       unsigned mul,
+		       int origx, int origy,
+		       int *xloc, int *yloc)
+{
+    int dx = 0, dy = 0;
+    int i;
+
+    for (i = 0; pixelvector[i] != '\0'; i++) {
+	switch (pixelvector[i]) {
+	case '0':
+	    dx += 1;
+	    break;
+	case '1':
+	    dx += 1;
+	    dy -= 1;
+	    break;
+	case '2':
+	    dy -= 1;
+	    break;
+	case '3':
+	    dx -= 1;
+	    dy -= 1;
+	    break;
+	case '4':
+	    dx -= 1;
+	    break;
+	case '5':
+	    dx -= 1;
+	    dy += 1;
+	    break;
+	case '6':
+	    dy += 1;
+	    break;
+	case '7':
+	    dx += 1;
+	    dy += 1;
+	    break;
+	default:
+	    break;
+	}
+    }
+
+    *xloc = origx + dx * (int) mul;
+    *yloc = origy + dy * (int) mul;
+
+    return 1;
+}
+
+static int
+load_regis_write_control(RegisParseState *state,
+			 Graphic const *graphic,
+			 int cur_x, int cur_y,
+			 int option,
+			 RegisDataFragment *arg,
+			 RegisWriteControls *out)
+{
+    TRACE(("checking write control option \"%c\" with arg \"%s\"\n",
+	   option, fragment_to_tempstr(arg)));
+    switch (option) {
+    case 'E':
+    case 'e':
+	TRACE(("write control erase writing mode \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	out->write_style = WRITE_STYLE_ERASE;
+	break;
+    case 'F':
+    case 'f':
+	TRACE(("write control plane write mask \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	{
+	    int val;
+	    if (!regis_num_to_int(arg, &val) ||
+		val < 0 || val >= (int) graphic->valid_registers) {
+		TRACE(("interpreting out of range value as 0 FIXME\n"));
+		out->plane_mask = 0U;
+	    } else {
+		out->plane_mask = (unsigned) val;
+	    }
+	}
+	break;
+    case 'I':
+    case 'i':
+	TRACE(("write control foreground color \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	if (!load_regis_colorspec(graphic, arg, &out->foreground)) {
+	    TRACE(("DATA_ERROR: write control foreground color specifier not recognized: \"%s\"\n",
+		   fragment_to_tempstr(arg)));
+	    return 0;
+	}
+	break;
+    case 'M':
+    case 'm':
+	TRACE(("write control found pixel multiplication factor \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	{
+	    int val;
+	    if (!regis_num_to_int(arg, &val) || val <= 0) {
+		TRACE(("interpreting out of range value %d as 1 FIXME\n", val));
+		out->pv_multiplier = 1U;
+	    } else {
+		out->pv_multiplier = (unsigned) val;
+	    }
+	}
+	break;
+    case 'N':
+    case 'n':
+	TRACE(("write control negative pattern control \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	{
+	    int val;
+	    if (!regis_num_to_int(arg, &val)) {
+		val = -1;
+	    }
+	    switch (val) {
+	    default:
+		TRACE(("interpreting out of range value %d as 0 FIXME\n", val));
+		out->invert_pattern = 0U;
+		break;
+	    case 0:
+		out->invert_pattern = 0U;
+		break;
+	    case 1:
+		out->invert_pattern = 1U;
+		break;
+	    }
+	}
+	break;
+    case 'P':
+    case 'p':
+	TRACE(("write control found pattern control \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	{
+	    RegisDataFragment suboptionset;
+	    RegisDataFragment suboptionarg;
+	    RegisDataFragment item;
+	    char suboption;
+
+	    while (arg->pos < arg->len) {
+		skip_regis_whitespace(arg);
+		TRACE(("looking for option in \"%s\"\n", fragment_to_tempstr(arg)));
+		if (extract_regis_optionset(arg, &suboptionset)) {
+		    TRACE(("got regis write pattern suboptionset: \"%s\"\n",
+			   fragment_to_tempstr(&suboptionset)));
+		    while (suboptionset.pos < suboptionset.len) {
+			skip_regis_whitespace(&suboptionset);
+			if (peek_fragment(&suboptionset) == ',') {
+			    pop_fragment(&suboptionset);
+			    continue;
+			}
+			if (extract_regis_option(&suboptionset, &suboption, &suboptionarg)) {
+			    TRACE(("inspecting write pattern suboption \"%c\" with value \"%s\"\n",
+				   suboption, fragment_to_tempstr(&suboptionarg)));
+			    switch (suboption) {
+			    case 'M':
+			    case 'm':
+				TRACE(("found pattern multiplier \"%s\"\n",
+				       fragment_to_tempstr(&suboptionarg)));
+				{
+				    RegisDataFragment num;
+				    int val;
+
+				    skip_regis_whitespace(&suboptionarg);
+				    if (extract_regis_num(&suboptionarg, &num)) {
+					if (!regis_num_to_int(&num, &val)
+					    || val < 1) {
+					    TRACE(("interpreting out of range pattern multiplier \"%s\" as 2 FIXME\n",
+						   fragment_to_tempstr(&num)));
+					    out->pattern_multiplier = 2U;
+					} else {
+					    out->pattern_multiplier =
+						(unsigned) val;
+					}
+				    }
+				    skip_regis_whitespace(&suboptionarg);
+				    if (fragment_len(&suboptionarg)) {
+					TRACE(("DATA_ERROR: unknown content after pattern multiplier \"%s\"\n",
+					       fragment_to_tempstr(&suboptionarg)));
+					return 0;
+				    }
+				}
+				break;
+			    default:
+				TRACE(("DATA_ERROR: unknown ReGIS write pattern suboption '%c' arg \"%s\"\n",
+				       suboption, fragment_to_tempstr(&suboptionarg)));
+				return 0;
+			    }
+			    continue;
+			}
+
+			TRACE(("DATA_ERROR: skipping unknown token in pattern control suboptionset (expecting option): \"%s\"\n",
+			       fragment_to_tempstr(&suboptionset)));
+			pop_fragment(&suboptionset);
+		    }
+		    continue;
+		}
+
+		TRACE(("looking for int in \"%s\"\n", fragment_to_tempstr(arg)));
+		if (extract_regis_num(arg, &item)) {
+		    if (peek_fragment(&item) == '0' ||
+			peek_fragment(&item) == '1') {
+			unsigned pattern = 0U;
+			unsigned bitcount;
+			char ch;
+
+			TRACE(("converting pattern bits \"%s\"\n",
+			       fragment_to_tempstr(&item)));
+			for (bitcount = 0;; bitcount++) {
+			    ch = pop_fragment(&item);
+			    if (ch == '\0')
+				break;
+			    switch (ch) {
+			    case '0':
+				if (bitcount < MAX_PATTERN_BITS) {
+				    pattern <<= 1U;
+				}
+				break;
+			    case '1':
+				if (bitcount < MAX_PATTERN_BITS) {
+				    pattern <<= 1U;
+				    pattern |= 1U;
+				}
+				break;
+			    default:
+				TRACE(("DATA_ERROR: unknown ReGIS write pattern bit value \"%c\"\n",
+				       ch));
+				return 0;
+			    }
+			}
+
+			if (bitcount > 0U) {
+			    unsigned extrabits;
+
+			    for (extrabits = 0;
+				 bitcount + extrabits < MAX_PATTERN_BITS;
+				 extrabits++) {
+				if (pattern & (1U << (bitcount - 1U))) {
+				    pattern <<= 1U;
+				    pattern |= 1U;
+				} else {
+				    pattern <<= 1U;
+				}
+			    }
+			}
+
+			out->pattern = pattern;
+		    } else {
+			int val;
+
+			TRACE(("converting pattern id \"%s\"\n",
+			       fragment_to_tempstr(&item)));
+			if (!regis_num_to_int(&item, &val))
+			    val = -1;
+			switch (val) {	/* FIXME: exponential allowed? */
+			case 0:
+			    out->pattern = 0x00;	/* solid bg */
+			    break;
+			case 1:
+			    out->pattern = 0xff;	/* solid fg */
+			    break;
+			case 2:
+			    out->pattern = 0xf0;	/* dash */
+			    break;
+			case 3:
+			    out->pattern = 0xe4;	/* dash dot */
+			    break;
+			case 4:
+			    out->pattern = 0xaa;	/* dot */
+			    break;
+			case 5:
+			    out->pattern = 0xea;	/* dash dot dot */
+			    break;
+			case 6:
+			    out->pattern = 0x88;	/* sparse dot */
+			    break;
+			case 7:
+			    out->pattern = 0x84;	/* asymmetric sparse dot */
+			    break;
+			case 8:
+			    out->pattern = 0xc8;	/* sparse dash dot */
+			    break;
+			case 9:
+			    out->pattern = 0x86;	/* sparse dot dash */
+			    break;
+			default:
+			    TRACE(("DATA_ERROR: unknown ReGIS standard write pattern \"%d\"\n", val));
+			    return 0;
+			}
+		    }
+
+		    TRACE(("final pattern is %02x\n", out->pattern));
+		    continue;
+		}
+
+		TRACE(("DATA_ERROR: skipping unknown token in pattern suboption: \"%s\"\n",
+		       fragment_to_tempstr(arg)));
+		pop_fragment(arg);
+	    }
+	}
+	break;
+    case 'C':
+    case 'c':
+	TRACE(("write control compliment writing mode \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	out->write_style = WRITE_STYLE_COMPLEMENT;
+	break;
+    case 'R':
+    case 'r':
+	TRACE(("write control switch to replacement writing mode \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	out->write_style = WRITE_STYLE_REPLACE;
+	break;
+    case 'S':
+    case 's':
+	TRACE(("write control shading control \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	{
+	    RegisDataFragment suboptionset;
+	    RegisDataFragment suboptionarg;
+	    RegisDataFragment item;
+	    char suboption;
+	    char shading_character = '\0';
+	    unsigned reference_dim = WRITE_SHADING_REF_Y;
+	    int ref_x = cur_x, ref_y = cur_y;
+	    int shading_enabled = 0;
+
+	    while (arg->pos < arg->len) {
+		skip_regis_whitespace(arg);
+
+		if (extract_regis_string(arg, state->temp, state->templen)) {
+		    TRACE(("found fill char \"%s\"\n", state->temp));
+		    /* FIXME: allow longer strings ignoring extra chars? */
+		    if (strlen(state->temp) != 1) {
+			TRACE(("DATA_ERROR: expected exactly one char in fill string FIXME\n"));
+			return 0;
+		    }
+		    shading_character = state->temp[0];
+		    TRACE(("shading character is: %d\n", (int) shading_character));
+		    continue;
+		}
+
+		if (extract_regis_optionset(arg, &suboptionset)) {
+		    TRACE(("got regis shading control suboptionset: \"%s\"\n",
+			   fragment_to_tempstr(&suboptionset)));
+		    while (suboptionset.pos < suboptionset.len) {
+			skip_regis_whitespace(&suboptionset);
+			if (peek_fragment(&suboptionset) == ',') {
+			    pop_fragment(&suboptionset);
+			    continue;
+			}
+			if (extract_regis_option(&suboptionset, &suboption, &suboptionarg)) {
+			    TRACE(("inspecting write shading suboption \"%c\" with value \"%s\"\n",
+				   suboption, fragment_to_tempstr(&suboptionarg)));
+			    switch (suboption) {
+			    case 'X':
+			    case 'x':
+				TRACE(("found vertical shading suboption \"%s\"\n",
+				       fragment_to_tempstr(&suboptionarg)));
+				if (fragment_len(&suboptionarg)) {
+				    TRACE(("DATA_ERROR: unexpected value to vertical shading suboption FIXME\n"));
+				    return 0;
+				}
+				reference_dim = WRITE_SHADING_REF_X;
+				break;
+			    default:
+				TRACE(("DATA_ERROR: unknown ReGIS write pattern suboption '%c' arg \"%s\"\n",
+				       suboption, fragment_to_tempstr(&suboptionarg)));
+				return 0;
+			    }
+			    continue;
+			}
+
+			TRACE(("DATA_ERROR: skipping unknown token in shading control suboptionset (expecting option): \"%s\"\n",
+			       fragment_to_tempstr(&suboptionset)));
+			pop_fragment(&suboptionset);
+		    }
+		    continue;
+		}
+
+		if (extract_regis_extent(arg, &item)) {
+		    if (!load_regis_extent(fragment_to_tempstr(&item),
+					   ref_x, ref_y,
+					   &ref_x, &ref_y)) {
+			TRACE(("DATA_ERROR: unable to parse extent in write shading option '%c': \"%s\"\n",
+			       option, fragment_to_tempstr(&item)));
+			return 0;
+		    }
+		    TRACE(("shading reference = %d,%d (%s)\n", ref_x, ref_y,
+			   ((reference_dim == WRITE_SHADING_REF_X)
+			    ? "X"
+			    : "Y")));
+		    continue;
+		}
+
+		if (extract_regis_num(arg, &item)) {
+		    if (!regis_num_to_int(&item, &shading_enabled)) {
+			TRACE(("DATA_ERROR: unable to parse int in write shading option '%c': \"%s\"\n",
+			       option, fragment_to_tempstr(&item)));
+			return 0;
+		    }
+		    if (shading_enabled < 0 || shading_enabled > 1) {
+			TRACE(("interpreting out of range value %d as 0 FIXME\n", shading_enabled));
+			shading_enabled = 0;
+		    }
+		    TRACE(("shading enabled = %d\n", shading_enabled));
+		    continue;
+		}
+
+		TRACE(("DATA_ERROR: skipping unknown token in shade suboption: \"%s\"\n",
+		       fragment_to_tempstr(arg)));
+		pop_fragment(arg);
+	    }
+
+	    if (shading_enabled) {
+		out->shading_enabled = 1U;
+		out->shading_reference_dim = reference_dim;
+		out->shading_reference = ((reference_dim == WRITE_SHADING_REF_X)
+					  ? ref_x
+					  : ref_y);
+		out->shading_character = shading_character;
+	    } else {
+		/* FIXME: confirm there is no effect if shading isn't enabled
+		 * in the same command
+		 */
+		out->shading_enabled = 0U;
+	    }
+	}
+	break;
+    case 'V':
+    case 'v':
+	TRACE(("write control switch to overlay writing mode \"%s\"\n",
+	       fragment_to_tempstr(arg)));
+	out->write_style = WRITE_STYLE_OVERLAY;
+	break;
+    default:
+	TRACE(("DATA_ERROR: ignoring unknown ReGIS write option \"%c\" arg \"%s\"\n",
+	       option, fragment_to_tempstr(arg)));
+	return 0;
+    }
+
+    return 1;
+}
+
+static int
+load_regis_write_control_set(RegisParseState *state,
+			     Graphic const *graphic,
+			     int cur_x, int cur_y,
+			     RegisDataFragment *controls,
+			     RegisWriteControls *out)
+{
+    RegisDataFragment optionset;
+    RegisDataFragment arg;
+    char option;
+
+    while (controls->pos < controls->len) {
+	skip_regis_whitespace(controls);
+
+	if (extract_regis_optionset(controls, &optionset)) {
+	    TRACE(("got regis write control optionset: \"%s\"\n",
+		   fragment_to_tempstr(&optionset)));
+	    while (optionset.pos < optionset.len) {
+		skip_regis_whitespace(&optionset);
+		if (peek_fragment(&optionset) == ',') {
+		    pop_fragment(&optionset);
+		    continue;
+		}
+		if (extract_regis_option(&optionset, &option, &arg)) {
+		    TRACE(("got regis write control option and value: \"%c\" \"%s\"\n",
+			   option, fragment_to_tempstr(&arg)));
+		    if (!load_regis_write_control(state, graphic,
+						  cur_x, cur_y,
+						  option, &arg, out)) {
+			return 0;
+		    }
+		    continue;
+		}
+
+		TRACE(("DATA_ERROR: skipping unknown token in write control optionset (expecting option): \"%s\"\n",
+		       fragment_to_tempstr(&optionset)));
+		pop_fragment(&optionset);
+	    }
+	    continue;
+	}
+
+	TRACE(("DATA_ERROR: skipping unknown token in write controls (expecting optionset): \"%s\"\n",
+	       fragment_to_tempstr(controls)));
+	pop_fragment(controls);
+    }
+
+    return 1;
+}
+
+static void
+init_regis_write_controls(int terminal_id, unsigned all_planes, RegisWriteControls *controls)
+{
+    controls->pv_multiplier = 1U;
+    controls->pattern = 0xff;	/* solid */
+    controls->pattern_multiplier = 2U;
+    controls->invert_pattern = 0U;
+    controls->plane_mask = all_planes;
+    controls->write_style = WRITE_STYLE_OVERLAY;
+    switch (terminal_id) {
+    case 125:			/* FIXME */
+    case 240:			/* FIXME */
+    case 241:			/* FIXME */
+    case 330:
+	controls->foreground = 3U;
+	break;
+    case 340:
+	controls->foreground = 7U;
+	break;
+    default:			/* FIXME */
+	controls->foreground = 63U;
+	break;
+    }
+    controls->shading_enabled = 0U;
+    controls->shading_character = '\0';
+    controls->shading_reference = 0;	/* no meaning if shading is disabled */
+    controls->shading_reference_dim = WRITE_SHADING_REF_Y;
+    /* FIXME: add the rest */
+}
+
+static void
+copy_regis_write_controls(RegisWriteControls const *src,
+			  RegisWriteControls *dst)
+{
+    dst->pv_multiplier = src->pv_multiplier;
+    dst->pattern = src->pattern;
+    dst->pattern_multiplier = src->pattern_multiplier;
+    dst->invert_pattern = src->invert_pattern;
+    dst->foreground = src->foreground;
+    dst->plane_mask = src->plane_mask;
+    dst->write_style = src->write_style;
+    dst->shading_enabled = src->shading_enabled;
+    dst->shading_character = src->shading_character;
+    dst->shading_reference = src->shading_reference;
+    dst->shading_reference_dim = src->shading_reference_dim;
+}
+
+static void
+init_regis_graphics_context(int terminal_id, RegisGraphicsContext *context)
+{
+    context->terminal_id = terminal_id;
+    /*
+     * Generate a mask covering all valid color register address bits
+     * (but don't bother past 2**16).
+     */
+    context->all_planes = (unsigned) context->graphic->valid_registers;
+    context->all_planes--;
+    context->all_planes |= 1U;
+    context->all_planes |= context->all_planes >> 1U;
+    context->all_planes |= context->all_planes >> 2U;
+    context->all_planes |= context->all_planes >> 4U;
+    context->all_planes |= context->all_planes >> 8U;
+
+    init_regis_write_controls(terminal_id, context->all_planes, &context->persistent_write_controls);
+    copy_regis_write_controls(&context->persistent_write_controls, &context->temporary_write_controls);
+
+    /* FIXME: coordinates */
+    /* FIXME: scrolling */
+    /* FIXME: output maps */
+    context->background = 0U;
+    /* FIXME: input cursor location */
+    /* FIXME: input cursor style */
+    context->graphics_output_cursor_x = 0;
+    context->graphics_output_cursor_y = 0;
+    /* FIXME: output cursor style */
+    /* FIXME: text settings */
+}
+
+static int
+parse_regis_command(RegisParseState *state)
+{
+    char ch = peek_fragment(&state->input);
+    if (ch == '\0')
+	return 0;
+
+    if (!extract_regis_command(&state->input, &ch))
+	return 0;
+
+    switch (ch) {
+    case 'C':
+    case 'c':
+	/* Curve
+
+	 * C
+	 * (A)  # set the arc length in degrees (+ or nothing for
+	 *      # counter-clockwise, - for clockwise, rounded to the
+	 *      # closest integer degree)
+	 * (B)  # begin closed curve sequence (must have at least two
+	 *      # values; this option can not be nested)
+	 * (C)  # position is the center, current location is the
+	 *      # circumference (stays in effect until next command)
+	 * (E)  # end curve sequence (drawing is performed here)
+	 * (S)  # begin open curve sequence
+	 * (W)  # temporary write options (see write command)
+	 * [<center, circumference position>]  # center if (C), otherwise point on circumference
+	 * [<point in curve sequence>]...  # if between (B) and (E)
+	 * <pv>...  # if between (B) and (E)
+	 */
+	TRACE(("found ReGIS command \"%c\" (curve)\n", ch));
+	state->command = 'c';
+	state->curve_mode = CURVE_POSITION_ARC_EDGE;
+	state->arclen = 360;
+	state->num_points = 0U;
+	break;
+    case 'F':
+    case 'f':
+	/* Fill
+
+	 * F
+	 * (V)  # polygon (see vector command)
+	 * (C)  # curve (see curve command)
+	 * (W)  # temporary write options (see write command)
+	 */
+	TRACE(("found ReGIS command \"%c\" (filled polygon)\n", ch));
+	state->command = 'f';
+	break;
+    case 'L':
+    case 'l':
+	/* Load
+
+	 * L
+	 * (A)  # set character set number and name
+	 * "ascii"xx,xx,xx,xx,xx,xx,xx,xx  # pixel values
+	 */
+	TRACE(("found ReGIS command \"%c\" (load charset)\n", ch));
+	state->command = 'l';
+	break;
+    case 'P':
+    case 'p':
+	/* Position
+
+	 * P
+	 * (B)  # begin bounded position stack (last point returns to first)
+	 * (E)  # end position stack
+	 * (S)  # begin unbounded position stack
+	 * (W)  # temporary write options (see write command)
+	 * <pv>  # move: 0 == right, 1 == upper right, ..., 7 == lower right
+	 * [<position>]  # move to position (X, Y, or both)
+	 *
+	 * Note the stack does not need to be ended before the next command
+	 * Note: maximum depth is 16 levels
+	 */
+	TRACE(("found ReGIS command \"%c\" (position)\n", ch));
+	state->command = 'p';
+	break;
+    case 'R':
+    case 'r':
+	/* Report
+
+	 * R
+	 * (E)  # parse error
+	 * (I<val>)  # set input mode (0 == oneshot, 1 == multiple) (always returns CR)
+	 * (L)  # character set
+	 * (M(<name>)  # macrograph contents
+	 * (M(=)  # macrograph storage
+	 * (P)  # cursor position
+	 * (P(I))  # interactive cursor position
+	 */
+	TRACE(("found ReGIS command \"%c\" (report status)\n", ch));
+	state->command = 'r';
+	break;
+    case 'S':
+    case 's':
+	/* Screen
+
+	 * S
+	 * (A[<upper left>][<lower right>])
+	 * (C<setting>  # 0 (cursor output off), 1 (cursor output on)
+	 * (E  # erase to background color, resets shades, curves, and stacks
+	 * (H(P<printer offset>)[<print area cornet>][<print area corner>)
+	 * (I<color register>)  # set the background to a specific register
+	 * (I(<rgb>))  # set the background to the register closest to an RGB value
+	 * (I(<hls>))  # set the background to the register closest to an HLS color
+	 * (M<color index to set>(L<mono level>)...)  # level is 0 ... 100 (sets grayscale registers only)
+	 * (M<color index to set>(<RGB code>)...)  # codes are D (black), R (red), G (green), B (blue), C (cyan), Y (yellow), M (magenta), W (white) (sets color and grayscale registers)
+	 * (M<color index to set>(A<RGB code>)...)  # codes are D (black), R (red), G (green), B (blue), C (cyan), Y (yellow), M (magenta), W (white) (sets color registers only)
+	 * (M<color index to set>(H<hue>L<lightness>S<saturation>)...)  # 0..360, 0..100, 0..100 (sets color and grayscale registers)
+	 * (M<color index to set>(AH<hue>L<lightness>S<saturation>)...)  # 0..360, 0..100, 0..100 (sets color registers only)
+	 * (P<graphics page number>)  # 0 (default) or 1
+	 * (T(<time delay ticks>)  # 60 ticks per second, up to 32767 ticks
+	 * (W(M<factor>)  # PV value
+	 * [scroll offset]  # optional
+	 */
+	TRACE(("found ReGIS command \"%c\" (screen)\n", ch));
+	state->command = 's';
+	break;
+    case 'T':
+    case 't':
+	/* Text
+
+	 * T
+	 * (A0L"<designator>"))  # specify a built-in set for GL via two-char designator
+	 * (A0R"<designator>"))  # specify a built-in set for GR via two-char or three-char designator
+	 * (A<num>R"<designator>"))  # specify a user-loaded (1-3) set for GR via two-char or three-char designator
+	 * (B)  # begin temporary text control
+	 * (D<angle>)  # specify a string tilt
+	 * (E)  # end temporary text control
+	 * (H<factor>)  # select a height multiplier (1-256)
+	 * (I<angle>)  # italics: no slant (0), lean back (-1 though -45), lean forward (+1 through +45)
+	 * (M[width factor,height factor])  # select size multipliers (width 1-16) (height 1-256)
+	 * (S<size id>)  # select one of the 17 standard cell sizes
+	 * (S[dimensions])  # set a custom display cell size (char with border)
+	 * (U[dimensions])  # set a custom unit cell size (char size)
+	 * (W<write command>)  # temporary write options (see write command)
+	 * [<char offset>]  # optional offset between characters
+	 * <PV spacing>  # for subscripts and superscripts
+	 * '<text>'  # optional
+	 * "<text>"  # optional
+	 */
+	TRACE(("found ReGIS command \"%c\" (text)\n", ch));
+	state->command = 't';
+	break;
+    case 'V':
+    case 'v':
+	/* Vector
+
+	 * V
+	 * (B)  # begin bounded position stack (last point returns to first)
+	 * (E)  # end position stack
+	 * (S)  # begin unbounded position stack
+	 * (W)  # temporary write options (see write command)
+	 * <pv>  # draw a line to the pixel vector
+	 * []  # draw a dot at the current location
+	 * [<position>]  # draw a line to position
+	 */
+	TRACE(("found ReGIS command \"%c\" (vector)\n", ch));
+	state->command = 'v';
+	break;
+    case 'W':
+    case 'w':
+	/* Write
+
+	 * W
+	 * (C)  # complement writing mode
+	 * (E)  # erase writing mode
+	 * (F<plane>)  # set the foreground intensity to a specific register
+	 * (I<color register>)  # set the foreground to a specific register
+	 * (I(<rgb>))  # set the foreground to the register closest to an RGB value
+	 * (I(<hls>))  # set the foreground to the register closest to an HLS color
+	 * (M<pixel vector multiplier>)  # set the multiplication factor
+	 * (N<setting>)  # 0 == negative patterns disabled, 1 == negative patterns enabled
+	 * (P<pattern number>)  # 0..9: 0 == none, 1 == solid, 2 == 50% dash, 3 == dash-dot
+	 * (P<pattern bits>)  # 2 to 8 bits represented as a 0/1 sequence
+	 * (P<(M<pattern multiplier>))
+	 * (R)  # replacement writing mode
+	 * (S'<character>')  # set shading character
+	 * (S<setting>)  # 0 == disable shding, 1 == enable shading
+	 * (S[reference point])  # set a horizontal reference line including this point
+	 * (S(X)[reference point])  # set a vertical reference line including this point
+	 * (V)  # overlay writing mode
+	 */
+	TRACE(("found ReGIS command \"%c\" (write parameters)\n", ch));
+	state->command = 'w';
+	break;
+    case '@':
+	/* Macrograph */
+	TRACE(("found ReGIS macrograph command\n"));
+	ch = pop_fragment(&state->input);
+	TRACE(("inspecting macrograph character \"%c\"\n", ch));
+	switch (ch) {
+	case '.':
+	    TRACE(("clearing all macrographs FIXME\n"));
+	    /* FIXME: handle */
+	    break;
+	case ':':
+	    TRACE(("defining macrograph FIXME\n"));
+	    /* FIXME: parse, handle  :<name> */
+	    break;
+	case ';':
+	    TRACE(("DATA_ERROR: found extraneous terminator for macrograph definition\n"));
+	    break;
+	default:
+	    if ((ch > 'A' && ch < 'Z') || (ch > 'a' && ch < 'z')) {
+		TRACE(("expanding macrograph \"%c\" FIXME\n", ch));
+		/* FIXME: handle */
+	    } else {
+		TRACE(("DATA_ERROR: unknown macrograph subcommand \"%c\"\n", ch));
+	    }
+	    /* FIXME: parse, handle */
+	    break;
+	}
+	break;
+    default:
+	TRACE(("DATA_ERROR: unknown ReGIS command %04x (%c)\n",
+	       (int) ch, ch));
+	state->command = '_';
+	state->option = '_';
+	return 0;
+    }
+
+    state->option = '_';
+
+    return 1;
+}
+
+static int
+parse_regis_optionset(RegisParseState *state)
+{
+    if (!extract_regis_optionset(&state->input, &state->optionset))
+	return 0;
+
+    TRACE(("found ReGIS optionset \"%s\"\n", fragment_to_tempstr(&state->optionset)));
+    state->option = '_';
+
+    return 1;
+}
+
+static int
+parse_regis_option(RegisParseState *state, RegisGraphicsContext *context)
+{
+    RegisDataFragment optionarg;
+
+    if (!extract_regis_option(&state->optionset, &state->option, &optionarg))
+	return 0;
+
+    TRACE(("found ReGIS option \"%c\": \"%s\"\n",
+	   state->option, fragment_to_tempstr(&optionarg)));
+
+    switch (state->command) {
+    case 'c':
+	TRACE(("inspecting curve option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	switch (state->option) {
+	case 'A':
+	case 'a':
+	    TRACE(("found arc length \"%s\"\n", fragment_to_tempstr(&optionarg)));
+	    {
+		RegisDataFragment arclen;
+
+		if (!extract_regis_num(&optionarg, &arclen)) {
+		    TRACE(("DATA_ERROR: expected int in curve arclen option: \"%s\"\n",
+			   fragment_to_tempstr(&arclen)));
+		    break;
+		}
+		TRACE(("arc length string %s\n", fragment_to_tempstr(&arclen)));
+		if (!regis_num_to_int(&arclen, &state->arclen)) {
+		    TRACE(("DATA_ERROR: unable to parse int in curve arclen option: \"%s\"\n",
+			   fragment_to_tempstr(&arclen)));
+		    break;
+		}
+		TRACE(("value of arc length is %d\n", state->arclen));
+		while (state->arclen < -360)
+		    state->arclen += 360;
+		while (state->arclen > 360)
+		    state->arclen -= 360;
+		TRACE(("using final arc length %d\n", state->arclen));
+	    }
+	    break;
+	case 'B':
+	case 'b':
+	    TRACE(("begin closed curve \"%s\"\n", fragment_to_tempstr(&optionarg)));
+	    if (fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: invalid closed curve option \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		break;
+	    }
+	    state->curve_mode = CURVE_POSITION_CLOSED_CURVE;
+	    state->num_points = 0U;
+	    state->x_points[state->num_points] = context->graphics_output_cursor_x;
+	    state->y_points[state->num_points] = context->graphics_output_cursor_y;
+	    state->num_points++;
+	    break;
+	case 'C':
+	case 'c':
+	    TRACE(("found center position mode \"%s\"\n",
+		   fragment_to_tempstr(&optionarg)));
+	    if (fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: invalid center position option \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		break;
+	    }
+	    state->curve_mode = CURVE_POSITION_ARC_CENTER;
+	    break;
+	case 'E':
+	case 'e':
+	    TRACE(("end curve \"%s\"\n", fragment_to_tempstr(&optionarg)));
+	    switch (state->curve_mode) {
+	    case CURVE_POSITION_CLOSED_CURVE:
+		{
+		    int i;
+
+#ifdef DEBUG_SPLINE_POINTS
+		    printf("points: \n");
+		    for (i = 0; i < (int) state->num_points; i++)
+			printf("  %d,%d\n",
+			       state->x_points[i], state->y_points[i]);
+#endif
+
+#ifdef DEBUG_SPLINE_WITH_ROTATION
+		    {
+			static int shift = 0;
+			int temp_x[MAX_CURVE_POINTS], temp_y[MAX_CURVE_POINTS];
+			shift++;
+			shift = shift % state->num_points;
+			for (i = 0; i < (int) state->num_points; i++) {
+			    temp_x[i] = state->x_points[i];
+			    temp_y[i] = state->y_points[i];
+			}
+			for (i = 0; i < (int) state->num_points; i++) {
+			    state->x_points[i] = temp_x[(i + shift) % state->num_points];
+			    state->y_points[i] = temp_y[(i + shift) % state->num_points];
+			}
+
+#ifdef DEBUG_SPLINE_POINTS
+			printf("after shift %d: \n", shift);
+			for (i = 0; i < (int) state->num_points; i++)
+			    printf("  %d,%d\n",
+				   state->x_points[i], state->y_points[i]);
+#endif
+		    }
+#endif
+
+		    for (i = (int) state->num_points; i > 0; i--) {
+			state->x_points[i] = state->x_points[i - 1];
+			state->y_points[i] = state->y_points[i - 1];
+		    }
+		    state->x_points[0] = state->x_points[state->num_points];
+		    state->y_points[0] = state->y_points[state->num_points];
+		    state->num_points++;
+		    for (i = (int) state->num_points; i > 0; i--) {
+			state->x_points[i] = state->x_points[i - 1];
+			state->y_points[i] = state->y_points[i - 1];
+		    }
+		    state->x_points[0] = state->x_points[state->num_points - 1];
+		    state->y_points[0] = state->y_points[state->num_points - 1];
+		    state->num_points++;
+		    state->x_points[state->num_points] = state->x_points[2];
+		    state->y_points[state->num_points] = state->y_points[2];
+		    state->num_points++;
+#ifdef DEBUG_SPLINE_WITH_OVERDRAW
+		    state->x_points[state->num_points] = state->x_points[3];
+		    state->y_points[state->num_points] = state->y_points[3];
+		    state->num_points++;
+		    state->x_points[state->num_points] = state->x_points[4];
+		    state->y_points[state->num_points] = state->y_points[4];
+		    state->num_points++;
+#endif
+#ifdef DEBUG_SPLINE_POINTS
+		    printf("after points added: \n");
+		    for (i = 0; i < (int) state->num_points; i++)
+			printf("  %d,%d\n",
+			       state->x_points[i], state->y_points[i]);
+#endif
+		}
+		TRACE(("drawing closed spline\n"));
+		global_context = context;	/* FIXME: remove after updating spline code */
+		plotCubicSpline((int) state->num_points - 1,
+				state->x_points, state->y_points,
+				1);
+		break;
+	    case CURVE_POSITION_OPEN_CURVE:
+		TRACE(("drawing open spline\n"));
+#ifdef DEBUG_SPLINE_POINTS
+		{
+		    int i;
+
+		    printf("points: \n");
+		    for (i = 0; i < (int) state->num_points; i++)
+			printf("  %d,%d\n",
+			       state->x_points[i], state->y_points[i]);
+		}
+#endif
+		global_context = context;	/* FIXME: remove after updating spline code */
+		plotCubicSpline((int) state->num_points - 1,
+				state->x_points, state->y_points,
+				1);
+		break;
+	    default:
+		TRACE(("DATA_ERROR: end curve option unexpected \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		break;
+	    }
+	    break;
+	case 'S':
+	case 's':
+	    TRACE(("begin open curve \"%s\"\n", fragment_to_tempstr(&optionarg)));
+	    if (fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: invalid open curve option \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		break;
+	    }
+	    state->curve_mode = CURVE_POSITION_OPEN_CURVE;
+	    state->num_points = 0U;
+	    state->x_points[state->num_points] = context->graphics_output_cursor_x;
+	    state->y_points[state->num_points] = context->graphics_output_cursor_y;
+	    state->num_points++;
+	    TRACE(("first point on curve with location %d,%d\n",
+		   context->graphics_output_cursor_x,
+		   context->graphics_output_cursor_y));
+	    break;
+	case 'W':
+	case 'w':
+	    TRACE(("found temporary write options \"%s\"\n",
+		   fragment_to_tempstr(&optionarg)));
+	    if (!load_regis_write_control_set(state, context->graphic,
+					      context->graphics_output_cursor_x, context->graphics_output_cursor_y,
+					      &optionarg, &context->temporary_write_controls)) {
+		TRACE(("DATA_ERROR: invalid temporary write options \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		break;
+	    }
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: ignoring unknown ReGIS curve command option '%c' arg \"%s\"\n",
+		   state->option, fragment_to_tempstr(&optionarg)));
+	    break;
+	}
+	break;
+    case 'f':
+	TRACE(("inspecting fill option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	switch (state->option) {
+	case 'C':
+	case 'c':
+	    state->command = 'c';
+	    state->option = '_';
+	    break;
+	case 'V':
+	case 'v':
+	    state->command = 'v';
+	    state->option = '_';
+	    break;
+	case 'W':
+	case 'w':
+	    TRACE(("found temporary write options \"%s\"\n",
+		   fragment_to_tempstr(&optionarg)));
+	    if (!load_regis_write_control_set(state, context->graphic,
+					      context->graphics_output_cursor_x, context->graphics_output_cursor_y,
+					      &optionarg, &context->temporary_write_controls)) {
+		TRACE(("DATA_ERROR: invalid temporary write options \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		break;
+	    }
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: ignoring unknown ReGIS fill command option '%c' arg \"%s\"\n",
+		   state->option, fragment_to_tempstr(&optionarg)));
+	    break;
+	}
+	break;
+    case 'l':
+	TRACE(("inspecting load option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	/* FIXME: parse options */
+	switch (state->option) {
+	case 'A':
+	case 'a':
+	    TRACE(("found character specifier option \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: ignoring unknown ReGIS load command option '%c' arg \"%s\"\n",
+		   state->option, fragment_to_tempstr(&optionarg)));
+	    break;
+	}
+	break;
+    case 'p':
+	TRACE(("inspecting position option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	switch (state->option) {
+	case 'B':
+	case 'b':
+	    TRACE(("found begin bounded position stack \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'E':
+	case 'e':
+	    TRACE(("found end position stack \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'S':
+	case 's':
+	    TRACE(("found begin unbounded position stack \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'W':
+	case 'w':
+	    TRACE(("found temporary write options \"%s\"\n",
+		   fragment_to_tempstr(&optionarg)));
+	    if (!load_regis_write_control_set(state, context->graphic,
+					      context->graphics_output_cursor_x, context->graphics_output_cursor_y,
+					      &optionarg, &context->temporary_write_controls)) {
+		TRACE(("DATA_ERROR: invalid temporary write options \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+	    }
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: ignoring unknown ReGIS position command option '%c' arg \"%s\"\n",
+		   state->option, fragment_to_tempstr(&optionarg)));
+	    break;
+	}
+	break;
+    case 'r':
+	TRACE(("inspecting report option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	switch (state->option) {
+	case 'E':
+	case 'e':
+	    TRACE(("found parse error report \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'I':
+	case 'i':
+	    TRACE(("found set input mode \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'L':
+	case 'l':
+	    TRACE(("found character set report \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'M':
+	case 'm':
+	    TRACE(("found macrograph report \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'P':
+	case 'p':
+	    TRACE(("found cursor position report \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: ignoring unknown ReGIS report command option '%c' arg \"%s\"\n",
+		   state->option, fragment_to_tempstr(&optionarg)));
+	    break;
+	}
+	break;
+    case 's':
+	TRACE(("inspecting screen option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	switch (state->option) {
+	case 'A':
+	case 'a':
+	    TRACE(("found address definition \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    if (!fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: ignoring malformed ReGIS screen address definition option value \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		return 0;
+	    }
+	    break;
+	case 'C':
+	case 'c':
+	    TRACE(("found cursor control \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    if (!fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: ignoring malformed ReGIS screen cursor control option value \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		return 0;
+	    }
+	    break;
+	case 'E':
+	case 'e':
+	    TRACE(("found erase request \"%s\"\n", fragment_to_tempstr(&optionarg)));
+	    if (fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: ignoring unexpected argument to ReGIS screen erase option \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		return 0;
+	    }
+	    draw_solid_rectangle(context->graphic, 0, 0,
+				 context->graphic->actual_width - 1,
+				 context->graphic->actual_height - 1,
+				 context->background);
+	    break;
+	case 'H':
+	case 'h':
+	    TRACE(("found hardcopy control \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    if (!fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: ignoring malformed ReGIS screen hardcopy control option value \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		return 0;
+	    }
+	    break;
+	case 'I':
+	case 'i':
+	    TRACE(("found screen background color index \"%s\"\n",
+		   fragment_to_tempstr(&optionarg)));
+	    if (!load_regis_colorspec(context->graphic, &optionarg, &context->background)) {
+		TRACE(("DATA_ERROR: screen background color specifier not recognized: \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		return 0;
+	    }
+	    break;
+	case 'M':
+	case 'm':
+	    TRACE(("found screen color register mapping \"%s\"\n",
+		   fragment_to_tempstr(&optionarg)));
+	    {
+		RegisDataFragment regnum;
+		RegisDataFragment colorspec;
+		char ch;
+
+		while (fragment_len(&optionarg)) {
+		    if (skip_regis_whitespace(&optionarg))
+			continue;
+		    if (extract_regis_num(&optionarg, &regnum)) {
+			int register_num;
+			int color_only;
+			short r, g, b;
+
+			if (!regis_num_to_int(&regnum, &register_num)) {
+			    TRACE(("DATA_ERROR: unable to parse int in screen color register mapping option: \"%s\"\n",
+				   fragment_to_tempstr(&regnum)));
+			    return 0;
+			}
+			if (register_num < 0 ||
+			    register_num > (int) context->graphic->valid_registers) {
+			    TRACE(("interpreting out of range register number %d as 0 FIXME\n", register_num));
+			    register_num = 0;
+			}
+			skip_regis_whitespace(&optionarg);
+			if (!extract_regis_optionset(&optionarg, &colorspec)) {
+			    TRACE(("DATA_ERROR: expected to find optionset after register number: \"%s\"\n",
+				   fragment_to_tempstr(&optionarg)));
+			    return 0;
+			}
+
+			switch (peek_fragment(&colorspec)) {
+			case 'A':
+			case 'a':
+			    pop_fragment(&colorspec);
+			    color_only = 1;
+			    break;
+			default:
+			    color_only = 0;
+			    break;
+			}
+
+			TRACE(("mapping register %d to color spec: \"%s\"\n",
+			       register_num, fragment_to_tempstr(&colorspec)));
+			if (fragment_len(&colorspec) == 1) {
+			    short l;
+			    ch = pop_fragment(&colorspec);
+
+			    TRACE(("got regis RGB colorspec pattern: \"%s\"\n",
+				   fragment_to_tempstr(&colorspec)));
+			    switch (ch) {
+			    case 'D':
+			    case 'd':
+				r = 0;
+				g = 0;
+				b = 0;
+				l = 0;
+				break;
+			    case 'R':
+			    case 'r':
+				r = 100;
+				g = 0;
+				b = 0;
+				l = 46;
+				break;
+			    case 'G':
+			    case 'g':
+				r = 0;
+				g = 100;
+				b = 0;
+				l = 50;
+				break;
+			    case 'B':
+			    case 'b':
+				r = 0;
+				g = 0;
+				b = 100;
+				l = 50;
+				break;
+			    case 'C':
+			    case 'c':
+				r = 0;
+				g = 100;
+				b = 100;
+				l = 50;
+				break;
+			    case 'Y':
+			    case 'y':
+				r = 100;
+				g = 100;
+				b = 0;
+				l = 50;
+				break;
+			    case 'M':
+			    case 'm':
+				r = 100;
+				g = 0;
+				b = 100;
+				l = 50;
+				break;
+			    case 'W':
+			    case 'w':
+				r = 100;
+				g = 100;
+				b = 100;
+				l = 100;
+				break;
+			    default:
+				TRACE(("unknown RGB color name: \"%c\"\n", ch));
+				return 0;
+			    }
+			    if (context->terminal_id == 240 ||
+				context->terminal_id == 330) {
+				/* The VT240 and VT330 models force saturation to zero. */
+				hls2rgb(0, l, 0, &r, &g, &b);
+			    }
+			} else {
+			    short h, l, s;
+
+			    if (sscanf(fragment_to_tempstr(&colorspec),
+				       "%*1[Hh]%hd%*1[Ll]%hd%*1[Ss]%hd",
+				       &h, &l, &s) != 3) {
+				h = 0;
+				s = 0;
+				if (sscanf(fragment_to_tempstr(&colorspec),
+					   "%*1[Ll]%hd", &l) != 1) {
+				    TRACE(("unrecognized colorspec: \"%s\"\n",
+					   fragment_to_tempstr(&colorspec)));
+				    return 0;
+				}
+			    }
+			    if (context->terminal_id == 240 ||
+				context->terminal_id == 330) {
+				/* The VT240 and VT330 models force saturation to zero. */
+				h = 0;
+				s = 0;
+			    }
+			    hls2rgb(h, l, s, &r, &g, &b);
+			}
+
+			if (color_only &&
+			    (context->terminal_id == 240 ||
+			     context->terminal_id == 330))
+			    continue;
+			update_color_register(context->graphic,
+					      (RegisterNum) register_num,
+					      r, g, b);
+			continue;
+		    }
+
+		    TRACE(("DATA_ERROR: ignoring unexpected character in ReGIS screen color register mapping value \"%c\"\n",
+			   pop_fragment(&optionarg)));
+		    return 0;
+		}
+	    }
+	    break;
+	case 'P':
+	case 'p':
+	    TRACE(("found graphics page request \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    if (!fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: ignoring malformed ReGIS screen graphics page option value \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		return 0;
+	    }
+	    break;
+	case 'T':
+	case 't':
+	    TRACE(("found time delay \"%s\" FIXME\n", fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    if (!fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: ignoring malformed ReGIS screen time delay option value \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		return 0;
+	    }
+	    break;
+	case 'W':
+	case 'w':
+	    TRACE(("found PV \"%s\" FIXME\n", fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    if (!fragment_len(&optionarg)) {
+		TRACE(("DATA_ERROR: ignoring malformed ReGIS screen PV option value \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+		return 0;
+	    }
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: ignoring unknown ReGIS screen command option '%c' arg \"%s\"\n",
+		   state->option, fragment_to_tempstr(&optionarg)));
+	    break;
+	}
+	break;
+    case 't':
+	TRACE(("inspecting text option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	if (!fragment_len(&optionarg)) {
+	    TRACE(("DATA_ERROR: ignoring malformed ReGIS text command option value \"%s\"\n",
+		   fragment_to_tempstr(&optionarg)));
+	    return 0;
+	}
+	switch (state->option) {
+	case 'A':
+	case 'a':
+	    TRACE(("found character set specifier \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'B':
+	case 'b':
+	    TRACE(("found beginning of temporary text control \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'D':
+	case 'd':
+	    TRACE(("found string tilt control \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'E':
+	case 'e':
+	    TRACE(("found end of temporary text control \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'H':
+	case 'h':
+	    TRACE(("found height multiplier \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'I':
+	case 'i':
+	    TRACE(("found italic control \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'M':
+	case 'm':
+	    TRACE(("found size multiplier \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'S':
+	case 's':
+	    TRACE(("found custom display cell size \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'U':
+	case 'u':
+	    TRACE(("found custom display unit size \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: ignoring unknown ReGIS text command option '%c' arg \"%s\"\n",
+		   state->option, fragment_to_tempstr(&optionarg)));
+	    break;
+	}
+	break;
+    case 'v':
+	TRACE(("inspecting vector option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	switch (state->option) {
+	case 'B':
+	case 'b':
+	    TRACE(("found begin bounded position stack \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'E':
+	case 'e':
+	    TRACE(("found end position stack \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'S':
+	case 's':
+	    TRACE(("found begin unbounded position stack \"%s\" FIXME\n",
+		   fragment_to_tempstr(&optionarg)));
+	    /* FIXME: handle */
+	    break;
+	case 'W':
+	case 'w':
+	    TRACE(("found temporary write options \"%s\"\n",
+		   fragment_to_tempstr(&optionarg)));
+	    if (!load_regis_write_control_set(state, context->graphic,
+					      context->graphics_output_cursor_x, context->graphics_output_cursor_y,
+					      &optionarg, &context->temporary_write_controls)) {
+		TRACE(("DATA_ERROR: invalid temporary write options \"%s\"\n",
+		       fragment_to_tempstr(&optionarg)));
+	    }
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: ignoring unknown ReGIS vector command option '%c' arg \"%s\"\n",
+		   state->option, fragment_to_tempstr(&optionarg)));
+	    break;
+	}
+	break;
+    case 'w':
+	TRACE(("inspecting write option \"%c\" with value \"%s\"\n",
+	       state->option, fragment_to_tempstr(&optionarg)));
+	if (!load_regis_write_control(state, context->graphic,
+				      context->graphics_output_cursor_x, context->graphics_output_cursor_y,
+				      state->option, &optionarg, &context->persistent_write_controls)) {
+	    TRACE(("DATA_ERROR: invalid write options"));
+	}
+	break;
+    default:
+	TRACE(("DATA_ERROR: unexpected option in \"%c\" command: \"%s\"\n",
+	       state->command, fragment_to_tempstr(&optionarg)));
+	return 0;
+    }
+
+    return 1;
+}
+
+static int
+parse_regis_items(RegisParseState *state, RegisGraphicsContext *context)
+{
+    RegisDataFragment *input;
+    RegisDataFragment item;
+
+    switch (state->level) {
+    case INPUT:
+	input = &state->input;
+	break;
+    case OPTIONSET:
+	input = &state->optionset;
+	break;
+    default:
+	TRACE(("invalid parse level: %d\n", state->level));
+	return 0;
+    }
+
+    if (input->pos >= input->len)
+	return 0;
+
+    if (extract_regis_extent(input, &item)) {
+	TRACE(("found extent \"%s\"\n", fragment_to_tempstr(&item)));
+	switch (state->command) {
+	case 'c':
+	    {
+		int orig_x, orig_y;
+		int new_x, new_y;
+
+		if (state->num_points > 0) {
+		    orig_x = state->x_points[state->num_points - 1];
+		    orig_y = state->y_points[state->num_points - 1];
+		} else {
+		    orig_x = context->graphics_output_cursor_x;
+		    orig_y = context->graphics_output_cursor_y;
+		}
+		if (!load_regis_extent(fragment_to_tempstr(&item),
+				       orig_x, orig_y,
+				       &new_x, &new_y)) {
+		    TRACE(("DATA_ERROR: unable to parse extent in '%c' command: \"%s\"\n",
+			   state->command, fragment_to_tempstr(&item)));
+		    break;
+		}
+
+		switch (state->curve_mode) {
+		case CURVE_POSITION_ARC_CENTER:
+		case CURVE_POSITION_ARC_EDGE:
+		    {
+			double radians;
+			int degrees;
+			int c_x, c_y;
+			int e_x, e_y;
+
+			if (state->curve_mode == CURVE_POSITION_ARC_CENTER) {
+			    c_x = new_x;
+			    c_y = new_y;
+			    e_x = orig_x;
+			    e_y = orig_y;
+			} else {
+			    c_x = orig_x;
+			    c_y = orig_y;
+			    e_x = new_x;
+			    e_y = new_y;
+			}
+
+			radians = atan2((double) (new_y - orig_y),
+					(double) (new_x - orig_x));
+			degrees = (int) (360.0 * radians / (2.0 * M_PI));
+			if (degrees < 0)
+			    degrees += 360;
+
+			TRACE(("drawing arc centered at location %d,%d to location %d,%d from %d degrees for %d degrees\n",
+			       c_x, c_y,
+			       e_x, e_y,
+			       degrees, state->arclen));
+			draw_patterned_arc(context,
+					   c_x, c_y,
+					   e_x, e_y,
+					   degrees, state->arclen);
+		    }
+		    break;
+		case CURVE_POSITION_OPEN_CURVE:
+		case CURVE_POSITION_CLOSED_CURVE:
+		    if (state->num_points >= MAX_INPUT_CURVE_POINTS) {
+			TRACE(("DATA_ERROR: got curve point, but already have max points (%d)\n", state->num_points));
+			break;
+		    }
+		    state->x_points[state->num_points] = new_x;
+		    state->y_points[state->num_points] = new_y;
+		    state->num_points++;
+		    TRACE(("adding point to curve with location %d,%d\n",
+			   new_x, new_y));
+		    break;
+		default:
+		    TRACE(("ERROR: got position, but curve mode %d is unknown\n", state->curve_mode));
+		    break;
+		}
+	    }
+	    break;
+	case 'p':
+	    /* FIXME TRACE(("DATA_ERROR: ignoring pen command with no location\n")); */
+	    if (!load_regis_extent(fragment_to_tempstr(&item),
+				   context->graphics_output_cursor_x, context->graphics_output_cursor_y,
+				   &context->graphics_output_cursor_x, &context->graphics_output_cursor_y)) {
+		TRACE(("DATA_ERROR: unable to parse extent in '%c' command: \"%s\"\n",
+		       state->command, fragment_to_tempstr(&item)));
+		break;
+	    }
+	    TRACE(("moving pen to location %d,%d\n",
+		   context->graphics_output_cursor_x,
+		   context->graphics_output_cursor_y));
+	    break;
+	case 's':
+	    /* FIXME: parse, handle */
+	    TRACE(("extent in screen command FIXME\n"));
+	    break;
+	case 't':
+	    /* FIXME: parse, handle */
+	    TRACE(("extent in text command FIXME\n"));
+	    break;
+	case 'v':
+	    {
+		int orig_x, orig_y;
+
+		orig_x = context->graphics_output_cursor_x;
+		orig_y = context->graphics_output_cursor_y;
+		if (!load_regis_extent(fragment_to_tempstr(&item),
+				       orig_x, orig_y,
+				       &context->graphics_output_cursor_x, &context->graphics_output_cursor_y)) {
+		    TRACE(("DATA_ERROR: unable to parse extent in '%c' command: \"%s\"\n",
+			   state->command, fragment_to_tempstr(&item)));
+		    break;
+		}
+		TRACE(("drawing line to location %d,%d\n",
+		       context->graphics_output_cursor_x,
+		       context->graphics_output_cursor_y));
+		draw_patterned_line(context,
+				    orig_x, orig_y,
+				    context->graphics_output_cursor_x,
+				    context->graphics_output_cursor_y);
+	    }
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: unexpected extent in \"%c\" command: \"%s\"\n",
+		   state->command, fragment_to_tempstr(&item)));
+	    break;
+	}
+	return 1;
+    }
+
+    if (extract_regis_pixelvector(input, &item)) {
+	TRACE(("found pixel vector \"%s\"\n", fragment_to_tempstr(&item)));
+	switch (state->command) {
+	case 'c':
+	    /* FIXME: parse, handle */
+	    TRACE(("pixelvector in curve command FIXME\n"));
+	    break;
+	    /* FIXME: not sure if 'f' supports pvs */
+	case 'p':
+	    /* FIXME: error checking */
+	    if (!load_regis_pixelvector(fragment_to_tempstr(&item), context->temporary_write_controls.pv_multiplier,
+					context->graphics_output_cursor_x, context->graphics_output_cursor_y,
+					&context->graphics_output_cursor_x, &context->graphics_output_cursor_y)) {
+		TRACE(("DATA_ERROR: unable to parse pixel vector in '%c' command: \"%s\"\n",
+		       state->command, fragment_to_tempstr(&item)));
+		break;
+	    }
+	    TRACE(("moving pen to location %d,%d\n",
+		   context->graphics_output_cursor_x,
+		   context->graphics_output_cursor_y));
+	    break;
+	case 's':
+	    /* FIXME: parse, handle scroll argument */
+	    TRACE(("pixelvector in screen command FIXME\n"));
+	    break;
+	case 't':
+	    /* FIXME: parse, handle */
+	    TRACE(("pixelvector in text command FIXME\n"));
+	    break;
+	case 'v':
+	    /* FIXME: error checking */
+	    {
+		int orig_x, orig_y;
+
+		orig_x = context->graphics_output_cursor_x;
+		orig_y = context->graphics_output_cursor_y;
+		if (!load_regis_pixelvector(fragment_to_tempstr(&item), context->temporary_write_controls.pv_multiplier,
+					    orig_x, orig_y,
+					    &context->graphics_output_cursor_x, &context->graphics_output_cursor_y)) {
+		    TRACE(("DATA_ERROR: unable to parse pixel vector in '%c' command: \"%s\"\n",
+			   state->command, fragment_to_tempstr(&item)));
+		    break;
+		}
+		TRACE(("drawing line to location %d,%d\n",
+		       context->graphics_output_cursor_x,
+		       context->graphics_output_cursor_y));
+		draw_patterned_line(context, orig_x, orig_y,
+				    context->graphics_output_cursor_x,
+				    context->graphics_output_cursor_y);
+	    }
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: unexpected pixel vector in \"%c\" command: \"%s\"\n",
+		   state->command, fragment_to_tempstr(&item)));
+	    break;
+	}
+	return 1;
+    }
+
+    if (extract_regis_string(input, state->temp, state->templen)) {
+	switch (state->command) {
+	case 'l':
+	    TRACE(("found character to load: \"%s\" FIXME\n", state->temp));
+	    /* FIXME: handle */
+	case 't':
+	    TRACE(("found string to draw: \"%s\" FIXME\n", state->temp));
+	    /* FIXME: handle */
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: unexpected string in \"%c\" command: \"%s\"\n",
+		   state->command, state->temp));
+	    break;
+	}
+	return 1;
+    }
+
+    /* hex values */
+    if (state->command == 'l') {
+	char ch1 = peek_fragment(input);
+	char ch2 = peek_fragment(input);
+	if ((ch1 == '0' ||
+	     ch1 == '1' ||
+	     ch1 == '2' ||
+	     ch1 == '3' ||
+	     ch1 == '4' ||
+	     ch1 == '5' ||
+	     ch1 == '6' ||
+	     ch1 == '7' ||
+	     ch1 == '8' ||
+	     ch1 == '9' ||
+	     ch1 == 'a' ||
+	     ch1 == 'b' ||
+	     ch1 == 'c' ||
+	     ch1 == 'd' ||
+	     ch1 == 'e' ||
+	     ch1 == 'f' ||
+	     ch1 == 'A' ||
+	     ch1 == 'B' ||
+	     ch1 == 'C' ||
+	     ch1 == 'D' ||
+	     ch1 == 'E' ||
+	     ch1 == 'F') &&
+	    (ch2 == '0' ||
+	     ch2 == '1' ||
+	     ch2 == '2' ||
+	     ch2 == '3' ||
+	     ch2 == '4' ||
+	     ch2 == '5' ||
+	     ch2 == '6' ||
+	     ch2 == '7' ||
+	     ch2 == '8' ||
+	     ch2 == '9' ||
+	     ch2 == 'a' ||
+	     ch2 == 'b' ||
+	     ch2 == 'c' ||
+	     ch2 == 'd' ||
+	     ch2 == 'e' ||
+	     ch2 == 'f' ||
+	     ch2 == 'A' ||
+	     ch2 == 'B' ||
+	     ch2 == 'C' ||
+	     ch2 == 'D' ||
+	     ch2 == 'E' ||
+	     ch2 == 'F')) {
+	    /* FIXME: handle */
+	    TRACE(("found hex number: \"%c%c\" FIXME\n", ch1, ch2));
+	    pop_fragment(input);
+	    pop_fragment(input);
+	    if (peek_fragment(input) == ',')
+		pop_fragment(input);
+	    return 1;
+	}
+    }
+
+    return 0;
+}
+
+/*
+ * context:
+ * two pages of 800x480
+ * current page #
+ * current command
+ * persistent write options
+ * temporary write options
+ * output position stack
+ */
+void
+parse_regis(XtermWidget xw, ANSI *params, char const *string)
+{
+    TScreen *screen = TScreenOf(xw);
+    RegisGraphicsContext context;
+    RegisParseState state;
+    unsigned iterations;
+    int charrow = 0;
+    int charcol = 0;
+    unsigned type = 1;		/* FIXME: use page number */
+
+    (void) xw;
+    (void) string;
+    (void) params;
+
+    TRACE(("ReGIS vector graphics mode, params=%d\n", params->a_nparam));
+
+    init_fragment(&state.input, string);
+    init_fragment(&state.optionset, "");
+    state.level = INPUT;
+    state.templen = (unsigned) strlen(string) + 1U;
+    if (!(state.temp = malloc((size_t) state.templen))) {
+	TRACE(("Unable to allocate temporary buffer of size %u\n", state.templen));
+	return;
+    }
+    state.command = '_';
+    state.option = '_';
+
+    memset(&context, 0, sizeof(context));
+
+    context.graphic = get_new_or_matching_graphic(xw,
+						  charrow, charcol,
+						  800, 480,
+						  type);
+    init_regis_graphics_context(screen->terminal_id, &context);
+    context.graphic->valid = 1;
+    context.graphic->dirty = 1;
+    refresh_modified_displayed_graphics(screen);
+
+    iterations = 0U;
+    for (;;) {
+	state.level = INPUT;
+	TRACE(("parsing at top level: %d of %d (next char %c)\n",
+	       state.input.pos,
+	       state.input.len,
+	       peek_fragment(&state.input)));
+	if (skip_regis_whitespace(&state.input))
+	    continue;
+	iterations++;
+	if (parse_regis_command(&state)) {
+	    if (iterations > ITERATIONS_BEFORE_REFRESH) {
+		iterations = 0U;
+		refresh_modified_displayed_graphics(screen);
+	    }
+	    context.graphic->dirty = 1;
+	    /* FIXME: verify that these are the things reset on a new command */
+	    copy_regis_write_controls(&context.persistent_write_controls, &context.temporary_write_controls);
+	    context.pattern_count = 0U;
+	    context.pattern_bit = 1U;
+	    continue;
+	}
+	if (parse_regis_optionset(&state)) {
+	    state.level = OPTIONSET;
+	    TRACE(("parsing at optionset level: %d of %d\n",
+		   state.optionset.pos,
+		   state.optionset.len));
+	    for (;;) {
+		if (state.optionset.pos >= state.optionset.len)
+		    break;
+		TRACE(("looking at optionset character: \"%c\"\n",
+		       peek_fragment(&state.optionset)));
+		if (skip_regis_whitespace(&state.optionset))
+		    continue;
+		if (peek_fragment(&state.optionset) == ',') {
+		    pop_fragment(&state.optionset);
+		    continue;
+		}
+		if (parse_regis_option(&state, &context))
+		    continue;
+		if (parse_regis_items(&state, &context))
+		    continue;
+		if (state.optionset.pos >= state.optionset.len)
+		    break;
+		TRACE(("DATA_ERROR: skipping unknown token in optionset: \"%c\"\n",
+		       pop_fragment(&state.optionset)));
+		/* FIXME: suboptions */
+	    }
+	    state.option = '_';
+	    continue;
+	}
+	if (parse_regis_items(&state, &context))
+	    continue;
+	if (state.optionset.pos >= state.optionset.len)
+	    break;
+	TRACE(("DATA_ERROR: skipping unknown token at top level: \"%c\"\n",
+	       pop_fragment(&state.input)));
+    }
+
+    free(state.temp);
+
+    refresh_modified_displayed_graphics(screen);
+    TRACE(("DONE! Successfully parsed ReGIS data.\n"));
+}
diff --git a/app/xterm/graphics_regis.h b/app/xterm/graphics_regis.h
new file mode 100644
index 000000000..03758dec3
--- /dev/null
+++ b/app/xterm/graphics_regis.h
@@ -0,0 +1,48 @@
+/* $XTermId: graphics_regis.h,v 1.1 2014/04/11 19:36:41 Ross.Combs Exp $ */
+
+/*
+ * Copyright 2014 by Ross Combs
+ * Copyright 2014 by Thomas E. Dickey
+ *
+ *                         All Rights Reserved
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the name(s) of the above copyright
+ * holders shall not be used in advertising or otherwise to promote the
+ * sale, use or other dealings in this Software without prior written
+ * authorization.
+ */
+
+#ifndef included_graphics_regis_h
+#define included_graphics_regis_h
+/* *INDENT-OFF* */
+
+#include <ptyx.h>
+
+#if OPT_REGIS_GRAPHICS
+extern void parse_regis(XtermWidget xw, ANSI *params, char const *string);
+#else
+#define parse_regis(xw, params, string) /* nothing */
+#endif
+
+/* *INDENT-ON* */
+
+#endif /* included_graphics_regis_h */
diff --git a/app/xterm/graphics_sixel.c b/app/xterm/graphics_sixel.c
new file mode 100644
index 000000000..e82984d9b
--- /dev/null
+++ b/app/xterm/graphics_sixel.c
@@ -0,0 +1,640 @@
+/* $XTermId: graphics_sixel.c,v 1.8 2014/05/02 22:53:20 tom Exp $ */
+
+/*
+ * Copyright 2014 by Ross Combs
+ *
+ *                         All Rights Reserved
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the name(s) of the above copyright
+ * holders shall not be used in advertising or otherwise to promote the
+ * sale, use or other dealings in this Software without prior written
+ * authorization.
+ */
+
+#include <xterm.h>
+
+#include <stdio.h>
+#include <ctype.h>
+#include <stdlib.h>
+
+#include <data.h>
+#include <VTparse.h>
+#include <ptyx.h>
+
+#include <assert.h>
+#include <graphics.h>
+#include <graphics_sixel.h>
+
+/***====================================================================***/
+/*
+ * Parse numeric parameters which have the operator as a prefix rather than a
+ * suffix as in ANSI format.
+ *
+ *  #             0
+ *  #1            1
+ *  #1;           1
+ *  "1;2;640;480  4
+ *  #1;2;0;0;0    5
+ */
+static void
+parse_prefixedtype_params(ANSI *params, const char **string)
+{
+    const char *cp = *string;
+    ParmType nparam = 0;
+    int last_empty = 1;
+
+    memset(params, 0, sizeof(*params));
+    params->a_final = CharOf(*cp);
+    if (*cp != '\0')
+	cp++;
+
+    while (*cp != '\0') {
+	Char ch = CharOf(*cp);
+
+	if (isdigit(ch)) {
+	    last_empty = 0;
+	    if (nparam < NPARAM) {
+		params->a_param[nparam] =
+		    (ParmType) ((params->a_param[nparam] * 10)
+				+ (ch - '0'));
+	    }
+	} else if (ch == ';') {
+	    last_empty = 1;
+	    nparam++;
+	} else if (ch == ' ' || ch == '\r' || ch == '\n') {
+	    /* EMPTY */ ;
+	} else {
+	    break;
+	}
+	cp++;
+    }
+
+    *string = cp;
+    if (!last_empty)
+	nparam++;
+    if (nparam > NPARAM)
+	params->a_nparam = NPARAM;
+    else
+	params->a_nparam = nparam;
+}
+
+typedef struct {
+    RegisterNum current_register;
+    RegisterNum background;	/* current background color register or hole */
+    int aspect_vertical;
+    int aspect_horizontal;
+    int declared_width;		/* size as reported by the application */
+    int declared_height;	/* size as reported by the application */
+    int row;			/* context used during parsing */
+    int col;			/* context used during parsing */
+} SixelContext;
+
+/* sixel scrolling:
+ * VK100/GIGI ? (did it even support Sixel?)
+ * VT125      unsupported
+ * VT240      unsupported
+ * VT241      unsupported
+ * VT330      mode setting
+ * VT382      ?
+ * VT340      mode setting
+ * dxterm     ?
+ */
+
+static void
+init_sixel_background(Graphic *graphic, SixelContext const *context)
+{
+    int r, c;
+
+    TRACE(("initializing sixel background to size=%dx%d bgcolor=%hu\n",
+	   context->declared_width,
+	   context->declared_height,
+	   context->background));
+
+    if (context->background == COLOR_HOLE)
+	return;
+
+    for (r = 0; r < graphic->actual_height; r++) {
+	for (c = 0; c < graphic->actual_width; c++) {
+	    graphic->pixels[r * graphic->max_width + c] = context->background;
+	}
+    }
+    graphic->color_registers_used[context->background] = 1;
+}
+
+static void
+set_sixel(Graphic *graphic, SixelContext const *context, int sixel)
+{
+    RegisterNum color;
+    int pix;
+
+    color = context->current_register;
+    TRACE(("drawing sixel at pos=%d,%d color=%hu (hole=%d, [%d,%d,%d])\n",
+	   context->col,
+	   context->row,
+	   color,
+	   color == COLOR_HOLE,
+	   ((color != COLOR_HOLE)
+	    ? (unsigned) graphic->color_registers[color].r : 0U),
+	   ((color != COLOR_HOLE)
+	    ? (unsigned) graphic->color_registers[color].g : 0U),
+	   ((color != COLOR_HOLE)
+	    ? (unsigned) graphic->color_registers[color].b : 0U)));
+    for (pix = 0; pix < 6; pix++) {
+	if (context->col < graphic->max_width &&
+	    context->row + pix < graphic->max_height) {
+	    if (sixel & (1 << pix)) {
+		if (context->col + 1 > graphic->actual_width) {
+		    graphic->actual_width = context->col + 1;
+		}
+		if (context->row + pix + 1 > graphic->actual_height) {
+		    graphic->actual_height = context->row + pix + 1;
+		}
+		graphic->pixels[
+				   (((context->row + pix) * graphic->max_width)
+				    + context->col)
+		    ] = color;
+	    }
+	} else {
+	    TRACE(("sixel pixel %d out of bounds\n", pix));
+	}
+    }
+}
+
+static void
+update_sixel_aspect(SixelContext const *context, Graphic *graphic)
+{
+    /* We want to keep the ratio accurate but would like every pixel to have
+     * the same size so keep these as whole numbers.
+     */
+    /* FIXME: DEC terminals had pixels about twice as tall as they were wide,
+     * and it seems the VT125 and VT24x only used data from odd graphic rows.
+     * This means it basically cancels out if we ignore both, except that
+     * the even rows of pixels may not be written by the application such that
+     * they are suitable for display.  In practice this doesn't seem to be
+     * an issue but I have very few test files/programs.
+     */
+    if (context->aspect_vertical < context->aspect_horizontal) {
+	graphic->pixw = 1;
+	graphic->pixh = ((context->aspect_vertical
+			  + context->aspect_horizontal - 1)
+			 / context->aspect_horizontal);
+    } else {
+	graphic->pixw = ((context->aspect_horizontal
+			  + context->aspect_vertical - 1)
+			 / context->aspect_vertical);
+	graphic->pixh = 1;
+    }
+    TRACE(("sixel aspect ratio: an=%d ad=%d -> pixw=%d pixh=%d\n",
+	   context->aspect_vertical,
+	   context->aspect_horizontal,
+	   graphic->pixw,
+	   graphic->pixh));
+}
+
+/*
+ * Interpret sixel graphics sequences.
+ *
+ * Resources:
+ *  http://en.wikipedia.org/wiki/Sixel
+ *  http://vt100.net/docs/vt3xx-gp/chapter14.html
+ *  ftp://ftp.cs.utk.edu/pub/shuford/terminal/sixel_graphics_news.txt
+ *  ftp://ftp.cs.utk.edu/pub/shuford/terminal/all_about_sixels.txt
+ */
+void
+parse_sixel(XtermWidget xw, ANSI *params, char const *string)
+{
+    TScreen *screen = TScreenOf(xw);
+    Graphic *graphic;
+    SixelContext context;
+    Char ch;
+
+    switch (screen->terminal_id) {
+    case 240:
+    case 241:
+    case 330:
+    case 340:
+	context.aspect_vertical = 2;
+	context.aspect_horizontal = 1;
+	break;
+    case 382:
+	context.aspect_vertical = 1;
+	context.aspect_horizontal = 1;
+	break;
+    default:
+	context.aspect_vertical = 2;
+	context.aspect_horizontal = 1;
+	break;
+    }
+
+    context.declared_width = 0;
+    context.declared_height = 0;
+
+    context.row = 0;
+    context.col = 0;
+
+    /* default isn't white on the VT240, but not sure what it is */
+    context.current_register = 3;	/* FIXME: using green, but not sure what it should be */
+
+    if (xw->keyboard.flags & MODE_DECSDM) {
+	TRACE(("sixel scrolling enabled: inline positioning for graphic at %d,%d\n",
+	       screen->cur_row, screen->cur_col));
+	graphic = get_new_graphic(xw, screen->cur_row, screen->cur_col, 0U);
+    } else {
+	TRACE(("sixel scrolling disabled: inline positioning for graphic at %d,%d\n",
+	       0, 0));
+	graphic = get_new_graphic(xw, 0, 0, 0U);
+    }
+
+    {
+	int Pmacro = params->a_param[0];
+	int Pbgmode = params->a_param[1];
+	int Phgrid = params->a_param[2];
+	int Pan = params->a_param[3];
+	int Pad = params->a_param[4];
+	int Ph = params->a_param[5];
+	int Pv = params->a_param[6];
+
+	(void) Phgrid;
+
+	TRACE(("sixel bitmap graphics sequence: params=%d (Pmacro=%d Pbgmode=%d Phgrid=%d) scroll_amt=%d\n",
+	       params->a_nparam,
+	       Pmacro,
+	       Pbgmode,
+	       Phgrid,
+	       screen->scroll_amt));
+
+	switch (params->a_nparam) {
+	case 7:
+	    if (Pan == 0 || Pad == 0) {
+		TRACE(("DATA_ERROR: invalid raster ratio %d/%d\n", Pan, Pad));
+		return;
+	    }
+	    context.aspect_vertical = Pan;
+	    context.aspect_horizontal = Pad;
+
+	    if (Ph == 0 || Pv == 0) {
+		TRACE(("DATA_ERROR: raster image dimensions are invalid %dx%d\n",
+		       Ph, Pv));
+		return;
+	    }
+	    if (Ph > graphic->max_width || Pv > graphic->max_height) {
+		TRACE(("DATA_ERROR: raster image dimensions are too large %dx%d\n",
+		       Ph, Pv));
+		return;
+	    }
+	    context.declared_width = Ph;
+	    context.declared_height = Pv;
+	    if (context.declared_width > graphic->actual_width) {
+		graphic->actual_width = context.declared_width;
+	    }
+	    if (context.declared_height > graphic->actual_height) {
+		graphic->actual_height = context.declared_height;
+	    }
+	    break;
+	case 3:
+	case 2:
+	case 1:
+	    switch (Pmacro) {
+	    case 0:
+		/* keep default aspect settings */
+		break;
+	    case 1:
+	    case 5:
+	    case 6:
+		context.aspect_vertical = 2;
+		context.aspect_horizontal = 1;
+		break;
+	    case 2:
+		context.aspect_vertical = 5;
+		context.aspect_horizontal = 1;
+		break;
+	    case 3:
+	    case 4:
+		context.aspect_vertical = 3;
+		context.aspect_horizontal = 1;
+		break;
+	    case 7:
+	    case 8:
+	    case 9:
+		context.aspect_vertical = 1;
+		context.aspect_horizontal = 1;
+		break;
+	    default:
+		TRACE(("DATA_ERROR: unknown sixel macro mode parameter\n"));
+		return;
+	    }
+	    break;
+	case 0:
+	    break;
+	default:
+	    TRACE(("DATA_ERROR: unexpected parameter count (found %d)\n", params->a_nparam));
+	    return;
+	}
+
+	if (Pbgmode == 1) {
+	    context.background = COLOR_HOLE;
+	} else {
+	    /* FIXME: is the default background register always zero?  what about in light background mode? */
+	    context.background = 0;
+	}
+
+	/* Ignore the grid parameter because it seems only printers paid attention to it.
+	 * The VT3xx was always 0.0195 cm.
+	 */
+    }
+
+    update_sixel_aspect(&context, graphic);
+
+    for (;;) {
+	ch = CharOf(*string);
+	if (ch == '\0')
+	    break;
+
+	if (ch >= 0x3f && ch <= 0x7e) {
+	    int sixel = ch - 0x3f;
+	    TRACE(("sixel=%x (%c)\n", sixel, (char) ch));
+	    if (!graphic->valid) {
+		init_sixel_background(graphic, &context);
+		graphic->valid = 1;
+	    }
+	    set_sixel(graphic, &context, sixel);
+	    context.col++;
+	} else if (ch == '$') {	/* DECGCR */
+	    /* ignore DECCRNLM in sixel mode */
+	    TRACE(("sixel CR\n"));
+	    context.col = 0;
+	} else if (ch == '-') {	/* DECGNL */
+	    int scroll_lines;
+	    TRACE(("sixel NL\n"));
+	    scroll_lines = 0;
+	    while (graphic->charrow - scroll_lines +
+		   (((context.row + 6) * graphic->pixh
+		     + FontHeight(screen) - 1)
+		    / FontHeight(screen)) > screen->bot_marg) {
+		scroll_lines++;
+	    }
+	    context.col = 0;
+	    context.row += 6;
+	    /* If we hit the bottom margin on the graphics page (well, we just use the
+	     * text margin for now), the behavior is to either scroll or to discard
+	     * the remainder of the graphic depending on this setting.
+	     */
+	    if (scroll_lines > 0) {
+		if (xw->keyboard.flags & MODE_DECSDM) {
+		    Display *display = screen->display;
+		    xtermScroll(xw, scroll_lines);
+		    XSync(display, False);
+		    TRACE(("graphic scrolled the screen %d lines. screen->scroll_amt=%d screen->topline=%d, now starting row is %d\n",
+			   scroll_lines,
+			   screen->scroll_amt,
+			   screen->topline,
+			   graphic->charrow));
+		} else {
+		    break;
+		}
+	    }
+	} else if (ch == '!') {	/* DECGRI */
+	    int Pcount;
+	    const char *start;
+	    int sixel;
+	    int i;
+
+	    start = ++string;
+	    for (;;) {
+		ch = CharOf(*string);
+		if (ch != '0' &&
+		    ch != '1' &&
+		    ch != '2' &&
+		    ch != '3' &&
+		    ch != '4' &&
+		    ch != '5' &&
+		    ch != '6' &&
+		    ch != '7' &&
+		    ch != '8' &&
+		    ch != '9' &&
+		    ch != ' ' &&
+		    ch != '\r' &&
+		    ch != '\n')
+		    break;
+		string++;
+	    }
+	    if (ch == '\0') {
+		TRACE(("DATA_ERROR: sixel data string terminated in the middle of a repeat operator\n"));
+		return;
+	    }
+	    if (string == start) {
+		TRACE(("DATA_ERROR: sixel data string contains a repeat operator with empty count\n"));
+		return;
+	    }
+	    Pcount = atoi(start);
+	    sixel = ch - 0x3f;
+	    TRACE(("sixel repeat operator: sixel=%d (%c), count=%d\n",
+		   sixel, (char) ch, Pcount));
+	    if (!graphic->valid) {
+		init_sixel_background(graphic, &context);
+		graphic->valid = 1;
+	    }
+	    for (i = 0; i < Pcount; i++) {
+		set_sixel(graphic, &context, sixel);
+		context.col++;
+	    }
+	} else if (ch == '#') {	/* DECGCI */
+	    ANSI color_params;
+	    int Pregister;
+
+	    parse_prefixedtype_params(&color_params, &string);
+	    Pregister = color_params.a_param[0];
+	    if (Pregister >= (int) graphic->valid_registers) {
+		TRACE(("DATA_WARNING: sixel color operator uses out-of-range register %d\n", Pregister));
+		/* FIXME: supposedly the DEC terminals wrapped register indicies -- verify */
+		while (Pregister >= (int) graphic->valid_registers)
+		    Pregister -= (int) graphic->valid_registers;
+		TRACE(("DATA_WARNING: converted to %d\n", Pregister));
+	    }
+
+	    if (color_params.a_nparam > 2 && color_params.a_nparam <= 5) {
+		int Pspace = color_params.a_param[1];
+		int Pc1 = color_params.a_param[2];
+		int Pc2 = color_params.a_param[3];
+		int Pc3 = color_params.a_param[4];
+		short r, g, b;
+
+		TRACE(("sixel set color register=%d space=%d color=[%d,%d,%d] (nparams=%d)\n",
+		       Pregister, Pspace, Pc1, Pc2, Pc3, color_params.a_nparam));
+
+		switch (Pspace) {
+		case 1:	/* HLS */
+		    if (Pc1 > 360 || Pc2 > 100 || Pc3 > 100) {
+			TRACE(("DATA_ERROR: sixel set color operator uses out-of-range HLS color coordinates %d,%d,%d\n",
+			       Pc1, Pc2, Pc3));
+			return;
+		    }
+		    hls2rgb(Pc1, Pc2, Pc3, &r, &g, &b);
+		    break;
+		case 2:	/* RGB */
+		    if (Pc1 > 100 || Pc2 > 100 || Pc3 > 100) {
+			TRACE(("DATA_ERROR: sixel set color operator uses out-of-range RGB color coordinates %d,%d,%d\n",
+			       Pc1, Pc2, Pc3));
+			return;
+		    }
+		    r = (short) Pc1;
+		    g = (short) Pc2;
+		    b = (short) Pc3;
+		    break;
+		default:	/* unknown */
+		    TRACE(("DATA_ERROR: sixel set color operator uses unknown color space %d\n", Pspace));
+		    return;
+		}
+		update_color_register(graphic,
+				      (RegisterNum) Pregister,
+				      r, g, b);
+	    } else if (color_params.a_nparam == 1) {
+		TRACE(("sixel switch to color register=%d (nparams=%d)\n",
+		       Pregister, color_params.a_nparam));
+		context.current_register = (RegisterNum) Pregister;
+	    } else {
+		TRACE(("DATA_ERROR: sixel switch color operator with unexpected parameter count (nparams=%d)\n", color_params.a_nparam));
+		return;
+	    }
+	    continue;
+	} else if (ch == '"') /* DECGRA */  {
+	    ANSI raster_params;
+
+	    parse_prefixedtype_params(&raster_params, &string);
+	    if (raster_params.a_nparam < 2) {
+		TRACE(("DATA_ERROR: sixel raster attribute operator with incomplete parameters (found %d, expected 2 or 4)\n", raster_params.a_nparam));
+		return;
+	    } {
+		int Pan = raster_params.a_param[0];
+		int Pad = raster_params.a_param[1];
+		TRACE(("sixel raster attribute with h:w=%d:%d\n", Pan, Pad));
+		if (Pan == 0 || Pad == 0) {
+		    TRACE(("DATA_ERROR: invalid raster ratio %d/%d\n", Pan, Pad));
+		    return;
+		}
+		context.aspect_vertical = Pan;
+		context.aspect_horizontal = Pad;
+		update_sixel_aspect(&context, graphic);
+	    }
+
+	    if (raster_params.a_nparam >= 4) {
+		int Ph = raster_params.a_param[2];
+		int Pv = raster_params.a_param[3];
+
+		TRACE(("sixel raster attribute with h=%d v=%d\n", Ph, Pv));
+		if (Ph == 0 || Pv == 0) {
+		    TRACE(("DATA_ERROR: raster image dimensions are invalid %dx%d\n",
+			   Ph, Pv));
+		    return;
+		}
+		if (Ph > graphic->max_width || Pv > graphic->max_height) {
+		    TRACE(("DATA_ERROR: raster image dimensions are too large %dx%d\n",
+			   Ph, Pv));
+		    return;
+		}
+		context.declared_width = Ph;
+		context.declared_height = Pv;
+		if (context.declared_width > graphic->actual_width) {
+		    graphic->actual_width = context.declared_width;
+		}
+		if (context.declared_height > graphic->actual_height) {
+		    graphic->actual_height = context.declared_height;
+		}
+	    }
+
+	    continue;
+	} else if (ch == ' ' || ch == '\r' || ch == '\n') {
+	    /* EMPTY */ ;
+	} else {
+	    TRACE(("DATA_ERROR: unknown sixel command %04x (%c)\n",
+		   (int) ch, ch));
+	}
+
+	string++;
+    }
+
+    /* update the screen */
+    if (screen->scroll_amt)
+	FlushScroll(xw);
+
+    if (xw->keyboard.flags & MODE_DECSDM) {
+	int new_row, new_col;
+
+	if (screen->sixel_scrolls_right) {
+	    new_row = (graphic->charrow
+		       + (((graphic->actual_height * graphic->pixh)
+			   + FontHeight(screen) - 1)
+			  / FontHeight(screen))
+		       - 1);
+	    new_col = (graphic->charcol
+		       + (((graphic->actual_width * graphic->pixw)
+			   + FontWidth(screen) - 1)
+			  / FontWidth(screen)));
+	} else {
+	    /* FIXME: At least of the VT382 the vertical position appears to be
+	     * truncated (rounded toward zero after converting to character row.
+	     * This code rounds up, which seems more useful, but it would be
+	     * better to be compatible.  Verify this is true on a VT3[34]0 as
+	     * well.
+	     */
+	    new_row = (graphic->charrow
+		       + (((graphic->actual_height * graphic->pixh)
+			   + FontHeight(screen) - 1)
+			  / FontHeight(screen)));
+	    new_col = 0;
+	}
+
+	TRACE(("setting text position after %dx%d graphic starting on row=%d col=%d: cursor new_row=%d new_col=%d\n",
+	       graphic->actual_width * graphic->pixw,
+	       graphic->actual_height * graphic->pixh,
+	       graphic->charrow,
+	       graphic->charcol,
+	       new_row, new_col));
+
+	if (new_col > screen->rgt_marg) {
+	    new_col = screen->lft_marg;
+	    new_row++;
+	    TRACE(("column past left margin, overriding to row=%d col=%d\n",
+		   new_row, new_col));
+	}
+
+	while (new_row > screen->bot_marg) {
+	    xtermScroll(xw, 1);
+	    new_row--;
+	    TRACE(("bottom row was past screen.  new start row=%d, cursor row=%d\n",
+		   graphic->charrow, new_row));
+	}
+
+	if (new_row < 0) {
+	    TRACE(("new row is going to be negative (%d)!", new_row));	/* FIXME: this was triggering, now it isn't */
+	    goto finis;
+	}
+	set_cur_row(screen, new_row);
+	set_cur_col(screen, new_col <= screen->rgt_marg ? new_col : screen->rgt_marg);
+    }
+
+  finis:
+    refresh_modified_displayed_graphics(screen);
+
+    TRACE(("DONE successfully parsed sixel data\n"));
+    dump_graphic(graphic);
+}
diff --git a/app/xterm/graphics_sixel.h b/app/xterm/graphics_sixel.h
new file mode 100644
index 000000000..54211389c
--- /dev/null
+++ b/app/xterm/graphics_sixel.h
@@ -0,0 +1,48 @@
+/* $XTermId: graphics_sixel.h,v 1.1 2014/04/11 19:36:41 Ross.Combs Exp $ */
+
+/*
+ * Copyright 2014 by Ross Combs
+ * Copyright 2014 by Thomas E. Dickey
+ *
+ *                         All Rights Reserved
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the name(s) of the above copyright
+ * holders shall not be used in advertising or otherwise to promote the
+ * sale, use or other dealings in this Software without prior written
+ * authorization.
+ */
+
+#ifndef included_graphics_sixel_h
+#define included_graphics_sixel_h
+/* *INDENT-OFF* */
+
+#include <ptyx.h>
+
+#if OPT_SIXEL_GRAPHICS
+extern void parse_sixel(XtermWidget xw, ANSI *params, char const *string);
+#else
+#define parse_sixel(xw, params, string) /* nothing */
+#endif
+
+/* *INDENT-ON* */
+
+#endif /* included_graphics_sixel_h */