[gtk: 37/40] GtkIconHelper: Preload icons for mapped widgets with higher priority

[Alexander Larsson <alexl src gnome org>]

commit b67d5822308a5dcd41423eb57acf41897df18d01
Author: Alexander Larsson <alexl redhat com>
Date:   Thu Jan 30 15:41:24 2020 +0100

    GtkIconHelper: Preload icons for mapped widgets with higher priority
    
    We look at whether a widget will be mapped (the actual state is not
    yet set, so we can't rely on that at css validation time) and use
    that to set the i/o priority of the async task.
    
    This means that its likely that widgets that will be displayed soon
    are loaded before those that are not yet going to be needed.

 gtk/gtkiconhelper.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkiconhelper.c b/gtk/gtkiconhelper.c
index a940b9f657..01ed8b4f41 100644
--- a/gtk/gtkiconhelper.c
+++ b/gtk/gtkiconhelper.c
@@ -175,6 +175,22 @@ gtk_icon_helper_load_paintable (GtkIconHelper   *self,
   return paintable;
 }
 
+/* We are calling this from css-validate, and the mapped state is not yet set, so
+ * we have to calculate ahead of time if a widget will be mapped. */
+static gboolean
+will_be_mapped (GtkWidget *widget)
+{
+  while (widget)
+    {
+      if (!_gtk_widget_get_visible (widget) ||
+          !_gtk_widget_get_child_visible (widget))
+        return FALSE;
+      widget = _gtk_widget_get_parent (widget);
+    }
+
+  return TRUE;
+}
+
 void
 _gtk_icon_helper_preload (GtkIconHelper *self)
 {
@@ -211,6 +227,7 @@ _gtk_icon_helper_preload (GtkIconHelper *self)
 
   if (gicon && G_IS_THEMED_ICON (gicon))
     {
+      int priority;
       style = gtk_css_node_get_style (self->node);
       icon_theme = gtk_css_icon_theme_value_get_icon_theme
         (gtk_css_style_get_value (style, GTK_CSS_PROPERTY_ICON_THEME));
@@ -219,10 +236,16 @@ _gtk_icon_helper_preload (GtkIconHelper *self)
       size = gtk_icon_helper_get_size (self);
       scale = gtk_widget_get_scale_factor (self->owner);
 
+      /* Icons for widgets are visible have higher priority so they are loaded first */
+      if (will_be_mapped (self->owner))
+        priority = G_PRIORITY_DEFAULT;
+      else
+        priority = G_PRIORITY_DEFAULT + 1;
+
       gtk_icon_theme_choose_icon_async (icon_theme,
                                         (const gchar **)g_themed_icon_get_names (G_THEMED_ICON (gicon)),
                                         size, scale,
-                                        flags, 0, NULL, NULL, NULL);
+                                        flags, priority, NULL, NULL, NULL);
     }
 
   if (free_gicon)