[gtk+] headerbar: compute nominal size of sides up front

[Ray Strode <halfline src gnome org>]

commit 847a43c4311c1952a5027381521120e3a817ee04
Author: Ray Strode <rstrode redhat com>
Date:   Fri Jun 24 12:16:40 2016 -0400

    headerbar: compute nominal size of sides up front
    
    In order to support the expand property on children, we're
    going to need to look at the size of the packed children
    on each side of the title widget, up front, before allocating
    them (to compute how much extra allocation each expanded child
    gets).
    
    This commit lays the groundwork for that analysis by splitting
    the size calculation of each side of the header bar outside
    of the loop that allocates each child of the header bar.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=724332

 gtk/gtkheaderbar.c |   28 ++++++++++++++++++++++------
 1 files changed, 22 insertions(+), 6 deletions(-)
---
diff --git a/gtk/gtkheaderbar.c b/gtk/gtkheaderbar.c
index eba695b..031199b 100644
--- a/gtk/gtkheaderbar.c
+++ b/gtk/gtkheaderbar.c
@@ -1074,7 +1074,28 @@ gtk_header_bar_allocate_contents (GtkCssGadget        *gadget,
 
   width = gtk_distribute_natural_allocation (MAX (0, width), nvis_children, sizes);
 
-  side[0] = side[1] = 0;
+  /* compute the nominal size of the children filling up each side of
+   * the title in titlebar
+   */
+  side[0] = start_width;
+  side[1] = end_width;
+  for (packing = GTK_PACK_START; packing <= GTK_PACK_END; packing++)
+    {
+      i = 0;
+      for (l = priv->children; l != NULL; l = l->next)
+        {
+          child = l->data;
+          if (!gtk_widget_get_visible (child->widget))
+            continue;
+
+          if (child->pack_type == packing)
+            side[packing] += sizes[i].minimum_size + priv->spacing;
+
+          i++;
+        }
+    }
+
+  /* allocate the children on both sides of the title */
   for (packing = GTK_PACK_START; packing <= GTK_PACK_END; packing++)
     {
       child_allocation.y = allocation->y;
@@ -1111,8 +1132,6 @@ gtk_header_bar_allocate_contents (GtkCssGadget        *gadget,
               x -= priv->spacing;
             }
 
-          side[packing] += child_size + priv->spacing;
-
           if (direction == GTK_TEXT_DIR_RTL)
             child_allocation.x = allocation->x + allocation->width - (child_allocation.x - allocation->x) - 
child_allocation.width;
 
@@ -1123,9 +1142,6 @@ gtk_header_bar_allocate_contents (GtkCssGadget        *gadget,
         }
     }
 
-  side[0] += start_width;
-  side[1] += end_width;
-
   /* We don't enforce css borders on the center widget, to make
    * title/subtitle combinations fit without growing the header
    */