[PATCH] DRI2: track drawable serial numbers

[Jesse Barnes]

If a pixmap header is modified or the drawable serial changes, some
aspects of the drawable are likely to have changed so we should
re-allocate the corresponding DRI2 drawable in that case.  This is one
way of catching when the root window pixmap changes through xrandr.

Fixes bug https://bugs.freedesktop.org/show_bug.cgi?id=28365.

Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>

diff --git a/hw/xfree86/dri2/dri2.c b/hw/xfree86/dri2/dri2.c
index f9ba8e7..e1238a5 100644
--- a/hw/xfree86/dri2/dri2.c
+++ b/hw/xfree86/dri2/dri2.c
@@ -82,6 +82,7 @@ typedef struct _DRI2Drawable {
     CARD64		 last_swap_msc; /* msc at completion of most recent swap */
     CARD64		 last_swap_ust; /* ust at completion of most recent swap */
     int			 swap_limit; /* for N-buffering */
+    unsigned long	 serialNumber;
 } DRI2DrawableRec, *DRI2DrawablePtr;
 
 typedef struct _DRI2Screen {
@@ -163,6 +164,7 @@ DRI2AllocateDrawable(DrawablePtr pDraw)
     pPriv->last_swap_msc = 0;
     pPriv->last_swap_ust = 0;
     list_init(&pPriv->reference_list);
+    pPriv->serialNumber = pDraw->serialNumber;
 
     if (pDraw->type == DRAWABLE_WINDOW) {
 	pWin = (WindowPtr) pDraw;
@@ -326,6 +328,7 @@ allocate_or_reuse_buffer(DrawablePtr pDraw, DRI2ScreenPtr ds,
 	|| !dimensions_match
 	|| (pPriv->buffers[old_buf]->format != format)) {
 	*buffer = (*ds->CreateBuffer)(pDraw, attachment, format);
+	pPriv->serialNumber = pDraw->serialNumber;
 	return TRUE;
 
     } else {
@@ -384,7 +387,8 @@ do_get_buffers(DrawablePtr pDraw, int *width, int *height,
     }
 
     dimensions_match = (pDraw->width == pPriv->width)
-	&& (pDraw->height == pPriv->height);
+	&& (pDraw->height == pPriv->height)
+	&& (pDraw->serialNumber == pPriv->serialNumber);
 
     buffers = malloc((count + 1) * sizeof(buffers[0]));