Ensure that vertical/horizontal segments do not overlap

Some drivers manage to optimize the solid block of segments into a
single square fill operation, which is a nifty optimization, but
doesn't really measure what we're interested here.

Signed-off-by: Keith Packard <keithp@keithp.com>
Part-of: <https://gitlab.freedesktop.org/xorg/test/x11perf/-/merge_requests/1>

2 files changed, 52 insertions, 63 deletions

diff --git a/do_segs.c b/do_segs.c
index 3c9c8f6..45b29fe 100644
--- a/do_segs.c
+++ b/do_segs.c
@@ -208,13 +208,11 @@ InitDoubleDashedSegments(XParms xp, Parms p, int64_t reps)
     return reps;
 }
 
-int
-InitHorizSegments(XParms xp, Parms p, int64_t reps)
+static int
+InitHorizSegmentsWidth(XParms xp, Parms p, int64_t reps, int width)
 {
     int     size;
-    int     half;
     int     i;
-    int     rows;       /* Number of rows filled in current column      */
     int     x, y;	/* base of square to draw in			*/
     int     y1;		/* y position inside square			*/
     int     inc;
@@ -223,39 +221,33 @@ InitHorizSegments(XParms xp, Parms p, int64_t reps)
     pgc = xp->fggc;
 
     size = p->special;
-    half = (size + 19) / 20;
 
     segments = malloc((p->objects) * sizeof(XSegment));
 
-    x = half;
-    y = half;
+    x = width / 2 + 1;
+    y = width / 2 + 1;
     y1 = 0;
-    rows = 0;
-    inc = size / p->objects;
-    if (inc == 0) inc = 1;
+    inc = width + 1;
 
     for (i = 0; i != p->objects; i++) {
 	if (i % 2) {
 	    segments[i].x1 = x + size;
 	    segments[i].x2 = x;
-	    segments[i].y1 = y + size - y1;
-	    segments[i].y2 = y + size - y1;
-	    y1 += inc;
-	    if (y1 >= size) y1 -= size;
+	    segments[i].y1 = y + (HEIGHT - width - 2) - y1;
+	    segments[i].y2 = y + (HEIGHT - width - 2) - y1;
+            y1 += inc;
 	} else {
 	    segments[i].x1 = x;
 	    segments[i].x2 = x + size;
 	    segments[i].y1 = y + y1;
 	    segments[i].y2 = y + y1;
 	}
-	rows++;
-	y += size;
-	if (y >= HEIGHT - size - half || rows == MAXROWS) {
-	    rows = 0;
-	    y = half;
-	    x += size;
-	    if (x >= WIDTH - size - half)
-		x = half;
+        /* Go to next row */
+	if (y1 >= HEIGHT / 2 - (width + 2)) {
+	    y1 =0;
+	    x += size + inc;
+	    if (x >= WIDTH - size - width)
+		x = width/2 + 1;
 	}
     }
     gcv.cap_style = CapNotLast;
@@ -265,13 +257,18 @@ InitHorizSegments(XParms xp, Parms p, int64_t reps)
 }
 
 int
+InitHorizSegments(XParms xp, Parms p, int64_t reps)
+{
+    return InitHorizSegmentsWidth(xp, p, reps, 1);
+}
+
+int
 InitWideHorizSegments(XParms xp, Parms p, int64_t reps)
 {
-    int size;
+    int size = p->special;
 
-    (void)InitHorizSegments(xp, p, reps);
+    (void)InitHorizSegmentsWidth(xp, p, reps, (int) ((size + 9) / 10));
 
-    size = p->special;
     XSetLineAttributes(xp->d, xp->bggc, (int) ((size + 9) / 10),
 	LineSolid, CapRound, JoinRound);
     XSetLineAttributes(xp->d, xp->fggc, (int) ((size + 9) / 10),
@@ -280,14 +277,11 @@ InitWideHorizSegments(XParms xp, Parms p, int64_t reps)
     return reps;
 }
 
-
-int
-InitVertSegments(XParms xp, Parms p, int64_t reps)
+static int
+InitVertSegmentsWidth(XParms xp, Parms p, int64_t reps, int width)
 {
     int     size;
-    int     half;
     int     i;
-    int     rows;       /* Number of rows filled in current column      */
     int     x, y;	/* base of square to draw in			*/
     int     x1;		/* x position inside square			*/
     int     inc;
@@ -296,41 +290,33 @@ InitVertSegments(XParms xp, Parms p, int64_t reps)
     pgc = xp->fggc;
 
     size = p->special;
-    half = (size + 19) / 20;
 
     segments = malloc((p->objects) * sizeof(XSegment));
 
-    x = half;
-    y = half;
+    x = width / 2 + 1;
+    y = width / 2 + 1;
     x1 = 0;
-    rows = 0;
-    inc = size / p->objects;
-    if (inc == 0) inc = 1;
+    inc = width + 1;
 
     for (i = 0; i != p->objects; i++) {
 	if (i % 2) {
-	    segments[i].x1 = x + size - x1;
-	    segments[i].x2 = x + size - x1;
+	    segments[i].x1 = x + (WIDTH - width - 2) - x1;
+	    segments[i].x2 = x + (WIDTH - width - 2) - x1;
 	    segments[i].y1 = y + size;
 	    segments[i].y2 = y;
-	    x1 += inc;
-	    if (x1 >= size) x1 -= size;
+            x1 += inc;
 	} else {
 	    segments[i].x1 = x + x1;
 	    segments[i].x2 = x + x1;
 	    segments[i].y1 = y;
 	    segments[i].y2 = y + size;
 	}
-	rows++;
-	y += size;
-	if (y >= HEIGHT - size - half || rows == MAXROWS) {
-	    /* Go to next column */
-	    rows = 0;
-	    y = half;
-	    x += size;
-	    if (x >= WIDTH - size - half) {
-		x = half;
-	    }
+        /* Go to next column */
+	if (x1 >= WIDTH / 2 - (width + 2)) {
+	    x1 = 0;
+            y += size + inc;
+            if (y >= HEIGHT - size - width)
+                y = width/2 + 1;
 	}
     }
     gcv.cap_style = CapNotLast;
@@ -340,13 +326,18 @@ InitVertSegments(XParms xp, Parms p, int64_t reps)
 }
 
 int
+InitVertSegments(XParms xp, Parms p, int64_t reps)
+{
+    return InitVertSegmentsWidth(xp, p, reps, 1);
+}
+
+int
 InitWideVertSegments(XParms xp, Parms p, int64_t reps)
 {
-    int size;
+    int    size = p->special;
 
-    (void)InitVertSegments(xp, p, reps);
+    (void)InitVertSegmentsWidth(xp, p, reps, (size + 9) / 10);
 
-    size = p->special;
     XSetLineAttributes(xp->d, xp->bggc, (int) ((size + 9) / 10),
 	LineSolid, CapRound, JoinRound);
     XSetLineAttributes(xp->d, xp->fggc, (int) ((size + 9) / 10),
@@ -355,7 +346,6 @@ InitWideVertSegments(XParms xp, Parms p, int64_t reps)
     return reps;
 }
 
-
 void
 DoSegments(XParms xp, Parms p, int64_t reps)
 {
@@ -380,4 +370,3 @@ EndSegments(XParms xp, Parms p)
 {
     free(segments);
 }
-
diff --git a/do_tests.c b/do_tests.c
index a1024e4..ebcc7cc 100644
--- a/do_tests.c
+++ b/do_tests.c
@@ -289,7 +289,7 @@ Test test[] = {
   {"-hseg500",  "500-pixel horizontal line segment", NULL,
 		InitHorizSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
-		{POLY, 500}},
+		{300, 500}},
   {"-vseg10",   "10-pixel vertical line segment", NULL,
 		InitVertSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
@@ -301,31 +301,31 @@ Test test[] = {
   {"-vseg500",  "500-pixel vertical line segment", NULL,
 		InitVertSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
-		{POLY, 500}},
+		{300, 500}},
   {"-whseg10",  "10x1 wide horizontal line segment", NULL,
 		InitWideHorizSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
-		{200, 10}},
+		{POLY, 10}},
   {"-whseg100", "100x10 wide horizontal line segment", NULL,
 		InitWideHorizSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
-		{100, 100}},
+		{270, 100}},
   {"-whseg500", "500x50 wide horizontal line segment", NULL,
 		InitWideHorizSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
-		{50, 500}},
+		{10, 500}},
   {"-wvseg10",  "10x1 wide vertical line segment", NULL,
 		InitWideVertSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
-		{200, 10}},
+		{POLY, 10}},
   {"-wvseg100", "100x10 wide vertical line segment", NULL,
 		InitWideVertSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
-		{100, 100}},
+		{270, 100}},
   {"-wvseg500", "500x50 wide vertical line segment", NULL,
 		InitWideVertSegments, DoSegments, NullProc, EndSegments,
 		V1_3FEATURE, ROP, 0,
-		{50, 500}},
+		{10, 500}},
   {"-line1",   "1-pixel line", NULL,
 		InitLines, DoLines, NullProc, EndLines,
 		V1_2FEATURE, ROP, 0,