dri2: No need to blit from front on DRI2GetBuffers if they're just being reused.

It can be quite an expensive operation, so we're better off not doing
it unless it's totally required.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>

1 files changed, 23 insertions, 19 deletions

diff --git a/hw/xfree86/dri2/dri2.c b/hw/xfree86/dri2/dri2.c
index cd69ca0c4..48618e1a5 100644
--- a/hw/xfree86/dri2/dri2.c
+++ b/hw/xfree86/dri2/dri2.c
@@ -202,27 +202,25 @@ find_attachment(DRI2DrawablePtr pPriv, unsigned attachment)
     return -1;
 }
 
-static DRI2BufferPtr
+static Bool
 allocate_or_reuse_buffer(DrawablePtr pDraw, DRI2ScreenPtr ds,
 			 DRI2DrawablePtr pPriv,
 			 unsigned int attachment, unsigned int format,
-			 int dimensions_match)
+			 int dimensions_match, DRI2BufferPtr *buffer)
 {
-    DRI2BufferPtr buffer;
-    int old_buf;
-
-    old_buf = find_attachment(pPriv, attachment);
+    int old_buf = find_attachment(pPriv, attachment);
 
     if ((old_buf < 0)
 	|| !dimensions_match
 	|| (pPriv->buffers[old_buf]->format != format)) {
-	buffer = (*ds->CreateBuffer)(pDraw, attachment, format);
+	*buffer = (*ds->CreateBuffer)(pDraw, attachment, format);
+	return TRUE;
+
     } else {
-	buffer = pPriv->buffers[old_buf];
+	*buffer = pPriv->buffers[old_buf];
 	pPriv->buffers[old_buf] = NULL;
+	return FALSE;
     }
-
-    return buffer;
 }
 
 static DRI2BufferPtr *
@@ -238,6 +236,7 @@ do_get_buffers(DrawablePtr pDraw, int *width, int *height,
     int have_fake_front = 0;
     int front_format = 0;
     int dimensions_match;
+    int buffers_changed = 0;
     int i;
 
     if (!pPriv) {
@@ -256,8 +255,10 @@ do_get_buffers(DrawablePtr pDraw, int *width, int *height,
 	const unsigned attachment = *(attachments++);
 	const unsigned format = (has_format) ? *(attachments++) : 0;
 
-	buffers[i] = allocate_or_reuse_buffer(pDraw, ds, pPriv, attachment,
-					      format, dimensions_match);
+	if (allocate_or_reuse_buffer(pDraw, ds, pPriv, attachment,
+				     format, dimensions_match,
+				     &buffers[i]))
+		buffers_changed = 1;
 
 	/* If the drawable is a window and the front-buffer is requested,
 	 * silently add the fake front-buffer to the list of requested
@@ -287,15 +288,18 @@ do_get_buffers(DrawablePtr pDraw, int *width, int *height,
     }
 
     if (need_real_front > 0) {
-	buffers[i++] = allocate_or_reuse_buffer(pDraw, ds, pPriv,
-						DRI2BufferFrontLeft,
-						front_format, dimensions_match);
+	if (allocate_or_reuse_buffer(pDraw, ds, pPriv, DRI2BufferFrontLeft,
+				     front_format, dimensions_match,
+				     &buffers[i++]))
+	    buffers_changed = 1;
     }
 
     if (need_fake_front > 0) {
-	buffers[i++] = allocate_or_reuse_buffer(pDraw, ds, pPriv,
-						DRI2BufferFakeFrontLeft,
-						front_format, dimensions_match);
+	if (allocate_or_reuse_buffer(pDraw, ds, pPriv, DRI2BufferFakeFrontLeft,
+				     front_format, dimensions_match,
+				     &buffers[i++]))
+	    buffers_changed = 1;
+
 	have_fake_front = 1;
     }
 
@@ -324,7 +328,7 @@ do_get_buffers(DrawablePtr pDraw, int *width, int *height,
      * contents of the real front-buffer.  This ensures correct operation of
      * applications that call glXWaitX before calling glDrawBuffer.
      */
-    if (have_fake_front) {
+    if (have_fake_front && buffers_changed) {
 	BoxRec box;
 	RegionRec region;