dix: Work around non-premultiplied ARGB cursor data

Some games incorrectly use non-premultiplied ARGB cursor data, presumably
because that's what Windows uses. On some hardware (and with SWcursor),
this breaks areas of the cursor which are supposed to be transparent
(and presumably also translucent areas, but that's less noticeable).

This change checks for pixels with alpha == 0 and any non-alpha component
!= 0. If any such pixel is found, the data is assumed to be
non-premultiplied and fixed up by multiplying the RGB components with the
alpha component.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92309
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/dix/cursor.c b/dix/cursor.c
index e45945619..25d676779 100644
--- a/dix/cursor.c
+++ b/dix/cursor.c
@@ -288,6 +288,29 @@ AllocARGBCursor(unsigned char *psrcbits, unsigned char *pmaskbits,
         goto error;
 
     *ppCurs = pCurs;
+
+    if (argb) {
+        size_t i, size = bits->width * bits->height;
+
+        for (i = 0; i < size; i++) {
+            if ((argb[i] & 0xff000000) == 0 && (argb[i] & 0xffffff) != 0) {
+                /* ARGB data doesn't seem pre-multiplied, fix it */
+                for (i = 0; i < size; i++) {
+                    CARD32 a, ar, ag, ab;
+
+                    a = argb[i] >> 24;
+                    ar = a * ((argb[i] >> 16) & 0xff) / 0xff;
+                    ag = a * ((argb[i] >> 8) & 0xff) / 0xff;
+                    ab = a * (argb[i] & 0xff) / 0xff;
+
+                    argb[i] = a << 24 | ar << 16 | ag << 8 | ab;
+                }
+
+                break;
+            }
+        }
+    }
+
     return Success;
 
  error: