[PATCH 4/9] dri2: Update front buffer pixmap and name before exchanging buffers

[Mario Kleiner]

Buffer exchange assumes that the front buffer pixmap and name
information is accurate. That may not be the case eg. if the window
has been (un)redirected since the buffer was created.

This is a translation to nouveau of a fix that was originally developed
by Ville Syrjala <syrjala at sci.fi> for the ati/radeon ddx to fix the
same bug there.

See thread at:

http://lists.x.org/archives/xorg-devel/2011-May/021908.html

Fixes FDO bug #35452.

Signed-off-by: Mario Kleiner <mario.kleiner at tuebingen.mpg.de>
---
 src/nouveau_dri2.c |   45 ++++++++++++++++++++++++++++++++++++++++++---
 1 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/src/nouveau_dri2.c b/src/nouveau_dri2.c
index 2908e56..8608678 100644
--- a/src/nouveau_dri2.c
+++ b/src/nouveau_dri2.c
@@ -149,6 +149,35 @@ struct nouveau_dri2_vblank_state {
 };
 
 static Bool
+update_front(DrawablePtr draw, DRI2BufferPtr front)
+{
+	int r;
+	PixmapPtr pixmap;
+	struct nouveau_dri2_buffer *nvbuf = nouveau_dri2_buffer(front);
+
+	if (draw->type == DRAWABLE_PIXMAP)
+		pixmap = (PixmapPtr)draw;
+	else
+		pixmap = (*draw->pScreen->GetWindowPixmap)((WindowPtr)draw);
+
+	pixmap->refcnt++;
+
+	exaMoveInPixmap(pixmap);
+	r = nouveau_bo_handle_get(nouveau_pixmap_bo(pixmap), &front->name);
+	if (r) {
+		(*draw->pScreen->DestroyPixmap)(pixmap);
+		return FALSE;
+	}
+
+	(*draw->pScreen->DestroyPixmap)(nvbuf->ppix);
+	front->pitch = pixmap->devKind;
+	front->cpp = pixmap->drawable.bitsPerPixel / 8;
+	nvbuf->ppix = pixmap;
+
+	return TRUE;
+}
+
+static Bool
 can_exchange(DrawablePtr draw, PixmapPtr dst_pix, PixmapPtr src_pix)
 {
 	ScrnInfoPtr scrn = xf86Screens[draw->pScreen->myNum];
@@ -234,13 +263,14 @@ nouveau_dri2_finish_swap(DrawablePtr draw, unsigned int frame,
 {
 	ScrnInfoPtr scrn = xf86Screens[draw->pScreen->myNum];
 	NVPtr pNv = NVPTR(scrn);
-	PixmapPtr dst_pix = nouveau_dri2_buffer(s->dst)->ppix;
+	PixmapPtr dst_pix;
 	PixmapPtr src_pix = nouveau_dri2_buffer(s->src)->ppix;
-	struct nouveau_bo *dst_bo = nouveau_pixmap_bo(dst_pix);
+	struct nouveau_bo *dst_bo;
 	struct nouveau_bo *src_bo = nouveau_pixmap_bo(src_pix);
 	struct nouveau_channel *chan = pNv->chan;
 	RegionRec reg;
 	int type, ret;
+	Bool front_updated;
 
 	REGION_INIT(0, &reg, (&(BoxRec){ 0, 0, draw->width, draw->height }), 0);
 	REGION_TRANSLATE(0, &reg, draw->x, draw->y);
@@ -257,6 +287,15 @@ nouveau_dri2_finish_swap(DrawablePtr draw, unsigned int frame,
 	if (ref_crtc_hw_id & 1)
 		ref_crtc_hw_id = 1;
 
+	/* Update frontbuffer pixmap and name: Could have changed due to
+	 * window (un)redirection as part of compositing.
+	 */
+	front_updated = update_front(draw, s->dst);
+
+	/* Assign frontbuffer pixmap, after update in update_front() */
+	dst_pix = nouveau_dri2_buffer(s->dst)->ppix;
+	dst_bo = nouveau_pixmap_bo(dst_pix);
+
 	/* Throttle on the previous frame before swapping */
 	nouveau_bo_map(dst_bo, NOUVEAU_BO_RD);
 	nouveau_bo_unmap(dst_bo);
@@ -275,7 +314,7 @@ nouveau_dri2_finish_swap(DrawablePtr draw, unsigned int frame,
 		FIRE_RING(chan);
 	}
 
-	if (can_exchange(draw, dst_pix, src_pix)) {
+	if (front_updated && can_exchange(draw, dst_pix, src_pix)) {
 		type = DRI2_EXCHANGE_COMPLETE;
 		DamageRegionAppend(draw, &reg);
 
-- 
1.7.5.4