From 55735cee2f05eca385f00c196bad05eb50c06822 Mon Sep 17 00:00:00 2001
From: Benjamin Otte <otte@redhat.com>
Date: Sat, 14 Nov 2015 18:28:34 +0100
Subject: [PATCH] window: Don't invalidate cssnode during get_preferred_width()

Getting the shadow width must not call gtk_style_context_set_state()
because that will invalidate the node and cause a style-updated emission
which can cause gtk_widget_queue_resize() calls.

And calling queue_resize() from get_preferred_size() essentially means
the size is permanently invalid because you invalidate it while
querying it.

This causes flickering of windows when going from/to backdrop state. To
avoid this we either need to fix the theme to not have different shadow
sizes in those cases or we need to ensure the window doesn't flicker in
the first place.
---
 gtk/gtkwindow.c | 51 +++++++++++++++++--------------------------------
 1 file changed, 18 insertions(+), 33 deletions(-)

diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index b52a2fafeb..db41f91e27 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -6717,9 +6717,8 @@ get_shadow_width (GtkWindow *window,
   GtkBorder d = { 0 };
   GtkBorder margin;
   GtkStyleContext *context;
-  GtkStateFlags state, s;
+  GtkStateFlags s;
   GtkCssValue *shadows;
-  gint i;
 
   *shadow_width = border;
 
@@ -6738,44 +6737,30 @@ get_shadow_width (GtkWindow *window,
   if (!_gtk_widget_is_toplevel (GTK_WIDGET (window)))
     return;
 
-  state = _gtk_widget_get_state_flags (GTK_WIDGET (window));
   context = _gtk_widget_get_style_context (GTK_WIDGET (window));
 
   gtk_style_context_save_to_node (context, priv->decoration_node);
+  s = gtk_style_context_get_state (context);
 
-  /* We don't want windows to jump as they go to backdrop,
-   * therefore we use the maximum of the decoration sizes
-   * for focused and unfocused.
-   */
-  for (i = 0; i < 2; i++)
+  /* Always sum border + padding */
+  gtk_style_context_get_border (context, s, &border);
+  gtk_style_context_get_padding (context, s, &d);
+  sum_borders (&d, &border);
+
+  /* Calculate the size of the drop shadows ... */
+  shadows = _gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_BOX_SHADOW);
+  _gtk_css_shadows_value_get_extents (shadows, &border);
+
+  if (priv->type != GTK_WINDOW_POPUP)
     {
-      if (i == 0)
-        s = state & ~GTK_STATE_FLAG_BACKDROP;
-      else
-        s = state | GTK_STATE_FLAG_BACKDROP;
-
-      gtk_style_context_set_state (context, s);
-
-      /* Always sum border + padding */
-      gtk_style_context_get_border (context, s, &border);
-      gtk_style_context_get_padding (context, s, &d);
-      sum_borders (&d, &border);
-
-      /* Calculate the size of the drop shadows ... */
-      shadows = _gtk_style_context_peek_property (context, GTK_CSS_PROPERTY_BOX_SHADOW);
-      _gtk_css_shadows_value_get_extents (shadows, &border);
-
-      if (priv->type != GTK_WINDOW_POPUP)
-        {
-          /* ... and compare it to the margin size, which we use for resize grips */
-          gtk_style_context_get_margin (context, s, &margin);
-          max_borders (&border, &margin);
-        }
-
-      sum_borders (&d, &border);
-      max_borders (shadow_width, &d);
+      /* ... and compare it to the margin size, which we use for resize grips */
+      gtk_style_context_get_margin (context, s, &margin);
+      max_borders (&border, &margin);
     }
 
+  sum_borders (&d, &border);
+  *shadow_width = d;
+
   gtk_style_context_restore (context);
 }