[goocanvas] Call gtk_widget_get_preferred_size() on child widgets to avoid GTK+ warnings.

[Damon Chaplin <damon src gnome org>]

commit 04c874bf46489cf5ab3abe0261a763a0f1974d83
Author: Damon Chaplin <Damon A Chaplin gmail com>
Date:   Thu Dec 15 10:41:14 2016 +0000

    Call gtk_widget_get_preferred_size() on child widgets to avoid GTK+ warnings.

 ChangeLog       |    5 +++++
 src/goocanvas.c |    4 ++++
 2 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index 5b50bf6..26fe9f2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2016-12-15  Damon Chaplin  <damon localhost lan>
+
+       * src/goocanvas.c (goo_canvas_allocate_child_widget): call
+       gtk_widget_get_preferred_size() to stop GTK+ spewing warnings.
+
 2016-12-14  Damon Chaplin  <damon gnome org>
 
        * src/goocanvas.c: added background_color and background_color_set
diff --git a/src/goocanvas.c b/src/goocanvas.c
index 0bafb56..a7f7463 100644
--- a/src/goocanvas.c
+++ b/src/goocanvas.c
@@ -2011,6 +2011,7 @@ goo_canvas_allocate_child_widget (GooCanvas       *canvas,
                                  GooCanvasWidget *witem)
 {
   GooCanvasBounds bounds;
+  GtkRequisition minimum_size;
   GtkAllocation allocation;
 
   goo_canvas_item_get_bounds ((GooCanvasItem*) witem, &bounds);
@@ -2018,6 +2019,9 @@ goo_canvas_allocate_child_widget (GooCanvas       *canvas,
   goo_canvas_convert_to_pixels (canvas, &bounds.x1, &bounds.y1);
   goo_canvas_convert_to_pixels (canvas, &bounds.x2, &bounds.y2);
 
+  /* Call this to stop GTK+ spewing warnings. */
+  gtk_widget_get_preferred_size (witem->widget, &minimum_size, NULL);
+
   /* Note that we only really support integers for the bounds, and we don't
      support scaling of a canvas with widget items in it. */
   allocation.x = bounds.x1;