[mutter] window: Defer stack placement without a buffer

[Olivier Fourdan <ofourdan src gnome org>]

commit bd9a3008014d1063aac75241ff750798cbe5aaee
Author: Olivier Fourdan <ofourdan redhat com>
Date:   Tue Jan 9 13:19:40 2018 +0100

    window: Defer stack placement without a buffer
    
    When closing a window and showing a new one, the new one may not be
    granted input focus until it gets a buffer on Wayland.
    
    If another window is chosen to receive focus and raised on top of stack,
    the newly mapped window is focused but placed underneath that other
    window.
    
    Meaning that for Wayland surfaces, we need to defer adding the window to
    the stack until we actually get to show it, once we have a buffer
    attached.
    
    Rather that checking the windowing backend prior to decide if a window
    is stackable or not, introduce a new vfunc is_stackable() which tells
    if a window should be added to the stack regardless of the underlying
    windowing system.
    
    Also add meta_window_is_in_stack() API rather than checking the stack
    position directly (replacing the define WINDOW_IN_STACK only available
    in stack.c) and remove a window from the stack only if it is present
    in the stack, so that the test in meta_stack_remote() becomes
    irrelevant.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=780820

 src/core/stack.c                  |   16 +++++-----------
 src/core/window-private.h         |    4 ++++
 src/core/window.c                 |   22 +++++++++++++++++++---
 src/wayland/meta-window-wayland.c |    7 +++++++
 src/x11/window-x11.c              |    7 +++++++
 5 files changed, 42 insertions(+), 14 deletions(-)
---
diff --git a/src/core/stack.c b/src/core/stack.c
index 5895b89..fc51aa1 100644
--- a/src/core/stack.c
+++ b/src/core/stack.c
@@ -49,8 +49,6 @@
 #define WINDOW_TRANSIENT_FOR_WHOLE_GROUP(w)                     \
   (WINDOW_HAS_TRANSIENT_TYPE (w) && w->transient_for == NULL)
 
-#define WINDOW_IN_STACK(w) (w->stack_position >= 0)
-
 static void stack_sync_to_xserver (MetaStack *stack);
 static void meta_window_set_stack_position_no_sync (MetaWindow *window,
                                                     int         position);
@@ -102,11 +100,11 @@ void
 meta_stack_add (MetaStack  *stack,
                 MetaWindow *window)
 {
-  g_return_if_fail (!window->override_redirect);
+  g_return_if_fail (meta_window_is_stackable (window));
 
   meta_topic (META_DEBUG_STACK, "Adding window %s to the stack\n", window->desc);
 
-  if (window->stack_position >= 0)
+  if (meta_window_is_in_stack (window))
     meta_bug ("Window %s had stack position already\n", window->desc);
 
   stack->added = g_list_prepend (stack->added, window);
@@ -127,10 +125,6 @@ meta_stack_remove (MetaStack  *stack,
 {
   meta_topic (META_DEBUG_STACK, "Removing window %s from the stack\n", window->desc);
 
-  if (window->stack_position < 0)
-    meta_bug ("Window %s removed from stack but had no stack position\n",
-              window->desc);
-
   /* Set window to top position, so removing it will not leave gaps
    * in the set of positions
    */
@@ -530,7 +524,7 @@ create_constraints (Constraint **constraints,
     {
       MetaWindow *w = tmp->data;
 
-      if (!WINDOW_IN_STACK (w))
+      if (!meta_window_is_in_stack (w))
         {
           meta_topic (META_DEBUG_STACK, "Window %s not in the stack, not constraining it\n",
                       w->desc);
@@ -557,7 +551,7 @@ create_constraints (Constraint **constraints,
             {
               MetaWindow *group_window = tmp2->data;
 
-              if (!WINDOW_IN_STACK (group_window) ||
+              if (!meta_window_is_in_stack (group_window) ||
                   w->screen != group_window->screen ||
                   group_window->override_redirect)
                 {
@@ -592,7 +586,7 @@ create_constraints (Constraint **constraints,
 
           parent = w->transient_for;
 
-          if (parent && WINDOW_IN_STACK (parent))
+          if (parent && meta_window_is_in_stack (parent))
             {
               meta_topic (META_DEBUG_STACK, "Constraining %s above %s due to transiency\n",
                           w->desc, parent->desc);
diff --git a/src/core/window-private.h b/src/core/window-private.h
index df38b2e..196e8af 100644
--- a/src/core/window-private.h
+++ b/src/core/window-private.h
@@ -553,6 +553,7 @@ struct _MetaWindowClass
                                    ClutterInputDevice *source);
   gboolean (*shortcuts_inhibited) (MetaWindow         *window,
                                    ClutterInputDevice *source);
+  gboolean (*is_stackable)        (MetaWindow *window);
 };
 
 /* These differ from window->has_foo_func in that they consider
@@ -699,6 +700,8 @@ void meta_window_set_type (MetaWindow     *window,
 
 void meta_window_frame_size_changed (MetaWindow *window);
 
+gboolean meta_window_is_in_stack (MetaWindow *window);
+
 void meta_window_stack_just_below (MetaWindow *window,
                                    MetaWindow *below_this_one);
 
@@ -795,4 +798,5 @@ void meta_window_force_restore_shortcuts (MetaWindow         *window,
 
 gboolean meta_window_shortcuts_inhibited (MetaWindow         *window,
                                           ClutterInputDevice *source);
+gboolean meta_window_is_stackable (MetaWindow *window);
 #endif
diff --git a/src/core/window.c b/src/core/window.c
index 5f13bf1..f664ef7 100644
--- a/src/core/window.c
+++ b/src/core/window.c
@@ -1298,10 +1298,10 @@ _meta_window_shared_new (MetaDisplay         *display,
    * and thus constraints may try to auto-fullscreen it which also
    * means restacking it.
    */
-  if (!window->override_redirect)
+  if (meta_window_is_stackable (window))
     meta_stack_add (window->screen->stack,
                     window);
-  else
+  else if (window->override_redirect)
     window->layer = META_LAYER_OVERRIDE_REDIRECT; /* otherwise set by MetaStack */
 
   if (!window->override_redirect)
@@ -1535,7 +1535,7 @@ meta_window_unmanage (MetaWindow  *window,
       meta_window_main_monitor_changed (window, old);
     }
 
-  if (!window->override_redirect)
+  if (meta_window_is_in_stack (window))
     meta_stack_remove (window->screen->stack, window);
 
   /* If an undecorated window is being withdrawn, that will change the
@@ -1698,6 +1698,10 @@ implement_showing (MetaWindow *window,
   meta_verbose ("Implement showing = %d for window %s\n",
                 showing, window->desc);
 
+  /* Some windows are not stackable until being showed, so add those now. */
+  if (meta_window_is_stackable (window) && !meta_window_is_in_stack (window))
+    meta_stack_add (window->screen->stack, window);
+
   if (!showing)
     {
       /* When we manage a new window, we normally delay placing it
@@ -6897,6 +6901,12 @@ ensure_mru_position_after (MetaWindow *window,
     }
 }
 
+gboolean
+meta_window_is_in_stack (MetaWindow *window)
+{
+  return window->stack_position >= 0;
+}
+
 void
 meta_window_stack_just_below (MetaWindow *window,
                               MetaWindow *below_this_one)
@@ -8425,3 +8435,9 @@ meta_window_shortcuts_inhibited (MetaWindow         *window,
 {
   return META_WINDOW_GET_CLASS (window)->shortcuts_inhibited (window, source);
 }
+
+gboolean
+meta_window_is_stackable (MetaWindow *window)
+{
+  return META_WINDOW_GET_CLASS (window)->is_stackable (window);
+}
diff --git a/src/wayland/meta-window-wayland.c b/src/wayland/meta-window-wayland.c
index f3f0e16..d5d8e21 100644
--- a/src/wayland/meta-window-wayland.c
+++ b/src/wayland/meta-window-wayland.c
@@ -543,6 +543,12 @@ meta_window_wayland_shortcuts_inhibited (MetaWindow         *window,
   return meta_wayland_compositor_is_shortcuts_inhibited (compositor, source);
 }
 
+static gboolean
+meta_window_wayland_is_stackable (MetaWindow *window)
+{
+  return meta_wayland_surface_get_buffer (window->surface) != NULL;
+}
+
 static void
 meta_window_wayland_class_init (MetaWindowWaylandClass *klass)
 {
@@ -562,6 +568,7 @@ meta_window_wayland_class_init (MetaWindowWaylandClass *klass)
   window_class->get_client_pid = meta_window_wayland_get_client_pid;
   window_class->force_restore_shortcuts = meta_window_wayland_force_restore_shortcuts;
   window_class->shortcuts_inhibited = meta_window_wayland_shortcuts_inhibited;
+  window_class->is_stackable = meta_window_wayland_is_stackable;
 }
 
 MetaWindow *
diff --git a/src/x11/window-x11.c b/src/x11/window-x11.c
index a553557..a8c53e8 100644
--- a/src/x11/window-x11.c
+++ b/src/x11/window-x11.c
@@ -1549,6 +1549,12 @@ meta_window_x11_shortcuts_inhibited (MetaWindow         *window,
   return FALSE;
 }
 
+static gboolean
+meta_window_x11_is_stackable (MetaWindow *window)
+{
+  return !window->override_redirect;
+}
+
 static void
 meta_window_x11_class_init (MetaWindowX11Class *klass)
 {
@@ -1572,6 +1578,7 @@ meta_window_x11_class_init (MetaWindowX11Class *klass)
   window_class->get_client_pid = meta_window_x11_get_client_pid;
   window_class->force_restore_shortcuts = meta_window_x11_force_restore_shortcuts;
   window_class->shortcuts_inhibited = meta_window_x11_shortcuts_inhibited;
+  window_class->is_stackable = meta_window_x11_is_stackable;
 }
 
 void