[PATCH 3/3] present: Do not replace Pixmaps on redirected Window on unflip

[Chris Wilson]

When unflipping, we may find that our flip window has been redirected.
If we replace the redirected Window with the Screen Pixmap we then have
mutliple fullscreen Windows believing that their own the Screen Pixmap -
multiple fullscreen Windows that are being flipped by Clients, and so
continue to flip causing popping between e.g. the compositor and the
game.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 present/present.c | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/present/present.c b/present/present.c
index a53dc11..ba88f79 100644
--- a/present/present.c
+++ b/present/present.c
@@ -374,12 +374,17 @@ present_set_tree_pixmap_visit(WindowPtr window, void *data)
 }
 
 static void
-present_set_tree_pixmap(WindowPtr window, PixmapPtr pixmap)
+present_set_tree_pixmap(WindowPtr window,
+                        PixmapPtr expected,
+                        PixmapPtr pixmap)
 {
     struct pixmap_visit visit;
     ScreenPtr           screen = window->drawable.pScreen;
 
     visit.old = (*screen->GetWindowPixmap)(window);
+    if (expected && visit.old != expected)
+        return;
+
     visit.new = pixmap;
     if (visit.old == visit.new)
         return;
@@ -390,6 +395,7 @@ static void
 present_set_abort_flip(ScreenPtr screen)
 {
     present_screen_priv_ptr screen_priv = present_screen_priv(screen);
+    PixmapPtr pixmap = (*screen->GetScreenPixmap)(screen);
 
     /* Switch back to using the screen pixmap now to avoid
      * 2D applications drawing to the wrong pixmap.
@@ -397,10 +403,11 @@ present_set_abort_flip(ScreenPtr screen)
 
     if (screen_priv->flip_window)
         present_set_tree_pixmap(screen_priv->flip_window,
-                                  (*screen->GetScreenPixmap)(screen));
+                                screen_priv->flip_pixmap,
+                                pixmap);
 
     if (screen->root)
-        present_set_tree_pixmap(screen->root, (*screen->GetScreenPixmap)(screen));
+        present_set_tree_pixmap(screen->root, NULL, pixmap);
 
     screen_priv->flip_pending->abort_flip = TRUE;
 }
@@ -414,10 +421,12 @@ present_unflip(ScreenPtr screen)
     assert (!screen_priv->unflip_event_id);
     assert (!screen_priv->flip_pending);
 
-    if (screen_priv->flip_window)
-        present_set_tree_pixmap(screen_priv->flip_window, pixmap);
+    if (screen_priv->flip_pixmap && screen_priv->flip_window)
+        present_set_tree_pixmap(screen_priv->flip_window,
+                                screen_priv->flip_pixmap,
+                                pixmap);
 
-    present_set_tree_pixmap(screen->root, pixmap);
+    present_set_tree_pixmap(screen->root, NULL, pixmap);
 
     /* Update the screen pixmap with the current flip pixmap contents
      */
@@ -645,9 +654,10 @@ present_execute(present_vblank_ptr vblank, uint64_t ust, uint64_t crtc_msc)
                  */
                 if (screen_priv->flip_window && screen_priv->flip_window != window)
                     present_set_tree_pixmap(screen_priv->flip_window,
-                                              (*screen->GetScreenPixmap)(screen));
-                present_set_tree_pixmap(window, pixmap);
-                present_set_tree_pixmap(screen->root, pixmap);
+                                            screen_priv->flip_pixmap,
+                                            (*screen->GetScreenPixmap)(screen));
+                present_set_tree_pixmap(window, NULL, pixmap);
+                present_set_tree_pixmap(screen->root, NULL, pixmap);
 
                 /* Report update region as damaged
                  */
-- 
2.1.4