ui: always set the frame background to None

This way the xserver never paints the frame background, even if
the client window is destroyed. This allows us to have clean
destroy window animation.

There is no problem with interactive resizing because applications
are using the XSync protocol, so we're not painting unless the
client has redrawn.

https://bugzilla.gnome.org/show_bug.cgi?id=734054

origin commit:
https://gitlab.gnome.org/GNOME/metacity/commit/78c283c

3 files changed, 12 insertions, 136 deletions

diff --git a/src/ui/frames.c b/src/ui/frames.c
index 87d075e9..5d76f42a 100644
--- a/src/ui/frames.c
+++ b/src/ui/frames.c
@@ -79,9 +79,6 @@ static void meta_frames_paint_to_drawable (MetaFrames   *frames,
                                            MetaUIFrame  *frame,
                                            cairo_t      *cr);
 
-static void meta_frames_set_window_background (MetaFrames   *frames,
-                                               MetaUIFrame  *frame);
-
 static void meta_frames_calc_geometry (MetaFrames        *frames,
                                        MetaUIFrame         *frame,
                                        MetaFrameGeometry *fgeom);
@@ -341,12 +338,6 @@ queue_recalc_func (gpointer key, gpointer value, gpointer data)
   frames = META_FRAMES (data);
   frame = value;
 
-  /* If a resize occurs it will cause a redraw, but the
-   * resize may not actually be needed so we always redraw
-   * in case of color change.
-   */
-  meta_frames_set_window_background (frames, frame);
-
   invalidate_whole_window (frames, frame);
   meta_core_queue_frame_resize (GDK_DISPLAY_XDISPLAY (gdk_display_get_default ()),
                                 frame->xwindow);
@@ -386,12 +377,6 @@ queue_draw_func (gpointer key, gpointer value, gpointer data)
   frames = META_FRAMES (data);
   frame = value;
 
-  /* If a resize occurs it will cause a redraw, but the
-   * resize may not actually be needed so we always redraw
-   * in case of color change.
-   */
-  meta_frames_set_window_background (frames, frame);
-
   invalidate_whole_window (frames, frame);
 }
 
@@ -607,11 +592,6 @@ meta_frames_manage_window (MetaFrames *frames,
   frame->shape_applied = FALSE;
   frame->prelit_control = META_FRAME_CONTROL_NONE;
 
-  /* Don't set the window background yet; we need frame->xwindow to be
-   * registered with its MetaWindow, which happens after this function
-   * and meta_ui_create_frame_window() return to meta_window_ensure_frame().
-   */
-
   meta_core_grab_buttons (GDK_DISPLAY_XDISPLAY (gdk_display_get_default ()), frame->xwindow);
 
   g_hash_table_replace (frames->frames, &frame->xwindow, frame);
@@ -732,52 +712,6 @@ meta_frames_get_geometry (MetaFrames *frames,
   *right_width *= scale;
 }
 
-void
-meta_frames_reset_bg (MetaFrames *frames,
-                      Window  xwindow)
-{
-  MetaUIFrame *frame;
-
-  frame = meta_frames_lookup_window (frames, xwindow);
-
-  meta_frames_set_window_background (frames, frame);
-}
-
-static void
-set_background_none (Display *xdisplay,
-                     Window   xwindow)
-{
-  XSetWindowAttributes attrs;
-
-  attrs.background_pixmap = None;
-  XChangeWindowAttributes (xdisplay, xwindow,
-                           CWBackPixmap, &attrs);
-}
-
-void
-meta_frames_unflicker_bg (MetaFrames *frames,
-                          Window      xwindow,
-                          int         target_width,
-                          int         target_height)
-{
-  MetaUIFrame *frame;
-
-  frame = meta_frames_lookup_window (frames, xwindow);
-  g_return_if_fail (frame != NULL);
-
-#if 0
-  pixmap = gdk_pixmap_new (frame->window,
-                           width, height,
-                           -1);
-
-  /* Oops, no way to get the background here */
-
-  meta_frames_paint_to_drawable (frames, frame, pixmap);
-#endif
-
-  set_background_none (GDK_DISPLAY_XDISPLAY (gdk_display_get_default ()), frame->xwindow);
-}
-
 #ifdef HAVE_SHAPE
 static void
 apply_cairo_region_to_window (Display        *display,
@@ -2506,52 +2440,6 @@ meta_frames_paint_to_drawable (MetaFrames   *frames,
                                     mini_icon, icon);
 }
 
-static void
-meta_frames_set_window_background (MetaFrames   *frames,
-                                   MetaUIFrame  *frame)
-{
-  MetaFrameFlags flags;
-  MetaFrameType type;
-  MetaFrameStyle *style;
-  gboolean frame_exists;
-
-  meta_core_get (GDK_DISPLAY_XDISPLAY (gdk_display_get_default ()), frame->xwindow,
-                 META_CORE_WINDOW_HAS_FRAME, &frame_exists,
-                 META_CORE_GET_FRAME_FLAGS, &flags,
-                 META_CORE_GET_FRAME_TYPE, &type,
-                 META_CORE_GET_END);
-
-  if (frame_exists)
-    {
-      style = meta_theme_get_frame_style (meta_theme_get_current (),
-                                          type, flags);
-    }
-
-  if (frame_exists && style->window_background_color != NULL)
-    {
-      GdkRGBA color;
-      GdkVisual *visual;
-
-      meta_color_spec_render (style->window_background_color,
-                              frame->style,
-                              &color);
-
-      /* Set A in ARGB to window_background_alpha, if we have ARGB */
-
-      visual = gtk_widget_get_visual (GTK_WIDGET (frames));
-      if (gdk_visual_get_depth (visual) == 32) /* we have ARGB */
-        {
-          color.alpha = style->window_background_alpha / 255.0;
-        }
-
-      gdk_window_set_background_rgba (frame->window, &color);
-    }
-  else
-    {
-      gtk_style_context_set_background (frame->style, frame->window);
-    }
- }
-
 static gboolean
 meta_frames_enter_notify_event      (GtkWidget           *widget,
                                      GdkEventCrossing    *event)
diff --git a/src/ui/frames.h b/src/ui/frames.h
index 8124a927..736c37ca 100644
--- a/src/ui/frames.h
+++ b/src/ui/frames.h
@@ -132,13 +132,6 @@ void meta_frames_get_geometry (MetaFrames *frames,
                                int *top_height, int *bottom_height,
                                int *left_width, int *right_width);
 
-void meta_frames_reset_bg     (MetaFrames *frames,
-                               Window      xwindow);
-void meta_frames_unflicker_bg (MetaFrames *frames,
-                               Window      xwindow,
-                               int         target_width,
-                               int         target_height);
-
 void meta_frames_apply_shapes (MetaFrames *frames,
                                Window      xwindow,
                                int         new_window_width,
diff --git a/src/ui/ui.c b/src/ui/ui.c
index f44b68cf..20e7546b 100644
--- a/src/ui/ui.c
+++ b/src/ui/ui.c
@@ -305,6 +305,17 @@ meta_ui_get_frame_geometry (MetaUI *ui,
                             left_width, right_width);
 }
 
+static void
+set_background_none (Display *xdisplay,
+                     Window   xwindow)
+{
+  XSetWindowAttributes attrs;
+
+  attrs.background_pixmap = None;
+  XChangeWindowAttributes (xdisplay, xwindow,
+                           CWBackPixmap, &attrs);
+}
+
 Window
 meta_ui_create_frame_window (MetaUI *ui,
                              Display *xdisplay,
@@ -363,6 +374,7 @@ meta_ui_create_frame_window (MetaUI *ui,
 		    &attrs, attributes_mask);
 
   gdk_window_resize (window, width, height);
+  set_background_none (xdisplay, GDK_WINDOW_XID (window));
 
   meta_frames_manage_window (ui->frames, GDK_WINDOW_XID (window), window);
 
@@ -418,16 +430,6 @@ meta_ui_unmap_frame (MetaUI *ui,
 }
 
 void
-meta_ui_unflicker_frame_bg (MetaUI *ui,
-                            Window  xwindow,
-                            int     target_width,
-                            int     target_height)
-{
-  meta_frames_unflicker_bg (ui->frames, xwindow,
-                            target_width, target_height);
-}
-
-void
 meta_ui_repaint_frame (MetaUI *ui,
                        Window xwindow)
 {
@@ -435,13 +437,6 @@ meta_ui_repaint_frame (MetaUI *ui,
 }
 
 void
-meta_ui_reset_frame_bg (MetaUI *ui,
-                        Window xwindow)
-{
-  meta_frames_reset_bg (ui->frames, xwindow);
-}
-
-void
 meta_ui_apply_frame_shape  (MetaUI  *ui,
                             Window   xwindow,
                             int      new_window_width,