lx_exa: Fix crash with solid fills on PictOpAdd operations

lx_check_composite has many special checks for PictOpAdd to return
successfully early, but these were done even earlier than the check
for solid fills. This resulted in lx_prepare_composite assuming
the source pixmap exists, which is not the case with solid fills.
Move the solid fill fallback checks before the others, so we are
guaranteed to always have a source pixmap in PrepareComposite and
Composite and don't crash trying to access a NULL pointer.

Also move up the mask check to do less checks in the PictOpAdd logic.

1 files changed, 11 insertions, 10 deletions

diff --git a/src/lx_exa.c b/src/lx_exa.c
index bcff23e..b341c51 100644
--- a/src/lx_exa.c
+++ b/src/lx_exa.c
@@ -547,28 +547,33 @@ lx_check_composite(int op, PicturePtr pSrc, PicturePtr pMsk, PicturePtr pDst)
     if (op > PictOpAdd)
         GEODE_FALLBACK(("Operation %d is not supported\n", op));
 
+    /* XXX - don't know if we can do any hwaccel on solid fills or gradient types */
+    if (pSrc->pSourcePict || (pMsk && pMsk->pSourcePict))
+        GEODE_FALLBACK(("Solid fills or gradient types are not supported\n"));
+
+    if (pMsk && op == PictOpAdd)
+        GEODE_FALLBACK(("PictOpAdd with mask is not supported\n"));
+
     /* FIXME: Meet this conditions from the debug for PictOpAdd.
      * Any Other possibilities? Add a judge for the future supplement */
     if (op == PictOpAdd && pSrc->format == PICT_a8r8g8b8 &&
-        pDst->format == PICT_a8 && !pMsk)
+        pDst->format == PICT_a8)
         return TRUE;
 
     if (op == PictOpAdd && pSrc->format == PICT_x8r8g8b8 &&
-        pDst->format == PICT_a8 && !pMsk)
+        pDst->format == PICT_a8)
         return TRUE;
 
     if (op == PictOpAdd && pSrc->format == PICT_r5g6b5 &&
-        pDst->format == PICT_a8 && !pMsk)
+        pDst->format == PICT_a8)
         return TRUE;
 
     if (usesPasses(op)) {
+        /* FIXME: Slightly misleading fallback msg when !pMsk */
         if (pGeode->exaBfrOffset == 0 || !pMsk)
             GEODE_FALLBACK(("Multipass operation requires off-screen buffer\n"));
     }
 
-    if (pMsk && op == PictOpAdd)
-        GEODE_FALLBACK(("PictOpAdd with mask is not supported\n"));
-
     /* Check that the filter matches what we support */
 
     switch (pSrc->filter) {
@@ -585,10 +590,6 @@ lx_check_composite(int op, PicturePtr pSrc, PicturePtr pMsk, PicturePtr pDst)
     if (pMsk && pMsk->transform)
         GEODE_FALLBACK(("Mask transforms are not supported\n"));
 
-    /* XXX - don't know if we can do any hwaccel on solid fills or gradient types */
-    if (pSrc->pSourcePict || (pMsk && pMsk->pSourcePict))
-        GEODE_FALLBACK(("Solid fills or gradient types are not supported\n"));
-
     /* Keep an eye out for source rotation transforms - those we can
      * do something about */