[gtk+] reftests: Ensure we got a draw event before quitting the main loop

[Benjamin Otte <otte src gnome org>]

commit 66f0544238c3bf64ed654db1d39701c3dc982f81
Author: Benjamin Otte <otte redhat com>
Date:   Thu May 5 05:13:34 2011 +0200

    reftests: Ensure we got a draw event before quitting the main loop

 tests/reftests/gtk-reftest.c |   19 ++++++++++++++++++-
 1 files changed, 18 insertions(+), 1 deletions(-)
---
diff --git a/tests/reftests/gtk-reftest.c b/tests/reftests/gtk-reftest.c
index 111a4c9..5b002f1 100644
--- a/tests/reftests/gtk-reftest.c
+++ b/tests/reftests/gtk-reftest.c
@@ -201,6 +201,18 @@ quit_when_idle (gpointer loop)
   return FALSE;
 }
 
+static void
+check_for_draw (GdkEvent *event, gpointer loop)
+{
+  if (event->type == GDK_EXPOSE)
+    {
+      g_idle_add (quit_when_idle, loop);
+      gdk_event_handler_set ((GdkEventFunc) gtk_main_do_event, NULL, NULL);
+    }
+
+  gtk_main_do_event (event);
+}
+
 static cairo_surface_t *
 snapshot_widget (GtkWidget *widget, SnapshotMode mode)
 {
@@ -217,7 +229,12 @@ snapshot_widget (GtkWidget *widget, SnapshotMode mode)
                                                gtk_widget_get_allocated_height (widget));
 
   loop = g_main_loop_new (NULL, FALSE);
-  g_idle_add (quit_when_idle, loop);
+  /* We wait until the widget is drawn for the first time.
+   * We can not wait for a GtkWidget::draw event, because that might not
+   * happen if the window is fully obscured by windowed child widgets.
+   * Alternatively, we could wait for an expose event on widget's window.
+   * Both of these are rather hairy, not sure what's best. */
+  gdk_event_handler_set (check_for_draw, loop, NULL);
   g_main_loop_run (loop);
 
   cr = cairo_create (surface);