[PATCH] present: recursively set window pixmaps on flip

[Keith Packard]

Newly created windows inherit the pixmap of their parent, similarly,
reparenting a tree inherits the pixmap of the destination tree.

Making present preserve the invariant that unredirected windows always
have the same pixmap as their parent ensures that the above cases work
correctly.

Signed-off-by: Keith Packard <keithp at keithp.com>
---
 present/present.c | 44 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 37 insertions(+), 7 deletions(-)

diff --git a/present/present.c b/present/present.c
index ffbb0b3..9ba1969 100644
--- a/present/present.c
+++ b/present/present.c
@@ -312,6 +312,36 @@ present_flip_idle(ScreenPtr screen)
     }
 }
 
+struct pixmap_visit {
+    PixmapPtr   old;
+    PixmapPtr   new;
+};
+
+static int
+present_set_window_pixmap_visit(WindowPtr window, pointer data)
+{
+    struct pixmap_visit *visit = data;
+    ScreenPtr           screen = window->drawable.pScreen;
+
+    if ((*screen->GetWindowPixmap)(window) != visit->old)
+        return WT_DONTWALKCHILDREN;
+    (*screen->SetWindowPixmap)(window, visit->new);
+    return WT_WALKCHILDREN;
+}
+    
+static void
+present_set_window_pixmap(WindowPtr window, PixmapPtr pixmap)
+{
+    struct pixmap_visit visit;
+    ScreenPtr           screen = window->drawable.pScreen;
+
+    visit.old = (*screen->GetWindowPixmap)(window);
+    visit.new = pixmap;
+    if (visit.old == visit.new)
+        return;
+    TraverseTree(window, present_set_window_pixmap_visit, &visit);
+}
+
 static void
 present_unflip(ScreenPtr screen)
 {
@@ -321,10 +351,10 @@ present_unflip(ScreenPtr screen)
     assert (!screen_priv->flip_pending);
 
     if (screen_priv->flip_window)
-        (*screen->SetWindowPixmap)(screen_priv->flip_window,
-                                   (*screen->GetScreenPixmap)(screen));
+        present_set_window_pixmap(screen_priv->flip_window,
+                                  (*screen->GetScreenPixmap)(screen));
 
-    (*screen->SetWindowPixmap)(screen->root, (*screen->GetScreenPixmap)(screen));
+    present_set_window_pixmap(screen->root, (*screen->GetScreenPixmap)(screen));
 
     /* Update the screen pixmap with the current flip pixmap contents
      */
@@ -527,10 +557,10 @@ present_execute(present_vblank_ptr vblank, uint64_t ust, uint64_t crtc_msc)
                  *  2) Set current flip window pixmap to the new pixmap
                  */
                 if (screen_priv->flip_window && screen_priv->flip_window != window)
-                    (*screen->SetWindowPixmap)(screen_priv->flip_window,
-                                               (*screen->GetScreenPixmap)(screen));
-                (*screen->SetWindowPixmap)(vblank->window, vblank->pixmap);
-                (*screen->SetWindowPixmap)(screen->root, vblank->pixmap);
+                    present_set_window_pixmap(screen_priv->flip_window,
+                                              (*screen->GetScreenPixmap)(screen));
+                present_set_window_pixmap(vblank->window, vblank->pixmap);
+                present_set_window_pixmap(screen->root, vblank->pixmap);
 
                 /* Report update region as damaged
                  */
-- 
1.8.4.4