[gtk+] pixel cache: Allow growing of cache surface

[Alexander Larsson <alexl src gnome org>]

commit 2d0bdee075edbbdcec9bc945db9c681ff927b002
Author: Alexander Larsson <alexl redhat com>
Date:   Mon Aug 26 21:13:05 2013 +0200

    pixel cache: Allow growing of cache surface
    
    If the new requested surface size is enough larger than the previous
    one (but the old is still larger than the absolute minimum),
    reallocate it anyway.
    
    This fixes an issue where the text view initially requested a really
    small extra size which was then increased but that didn't "take".

 gtk/gtkpixelcache.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/gtk/gtkpixelcache.c b/gtk/gtkpixelcache.c
index bffa618..fd44f20 100644
--- a/gtk/gtkpixelcache.c
+++ b/gtk/gtkpixelcache.c
@@ -26,8 +26,9 @@
    to make scrolling more efficient */
 #define DEFAULT_EXTRA_SIZE 64
 
-/* When resizing viewport to smaller we allow this extra
+/* When resizing viewport we allow this extra
    size to avoid constantly reallocating when resizing */
+#define ALLOW_SMALLER_SIZE 32
 #define ALLOW_LARGER_SIZE 32
 
 struct _GtkPixelCache {
@@ -184,9 +185,9 @@ _gtk_pixel_cache_create_surface_if_needed (GtkPixelCache         *cache,
   /* If current surface can't fit view_rect or is too large, kill it */
   if (cache->surface != NULL &&
       (cairo_surface_get_content (cache->surface) != content ||
-       cache->surface_w < view_rect->width ||
+       cache->surface_w < MAX(view_rect->width, surface_w - ALLOW_SMALLER_SIZE) ||
        cache->surface_w > surface_w + ALLOW_LARGER_SIZE ||
-       cache->surface_h < view_rect->height ||
+       cache->surface_h < MAX(view_rect->height, surface_h - ALLOW_SMALLER_SIZE) ||
        cache->surface_h > surface_h + ALLOW_LARGER_SIZE ||
        cache->surface_scale != gdk_window_get_scale_factor (window)))
     {