Cache heights-for-range-of-widths instead of height for every width.

This patch optimizes window resizes by assuming that if a widget
has the same height at a width of 50 as with a width of 150, the
height for width 100 will also be the same.

The patch also further optimizes the cache allocator, now there
are 2 pointer arrays of up to a maximum of 5 requests, the arrays
will only be allocated if a request is ever made in that orientation
and the array will be sparse until each request is made (i.e. if a
label can only wrap to 3 lines, there will only be 3 out of a
possible 5 SizeRequest structures allocated to cache it).

1 files changed, 21 insertions, 21 deletions

diff --git a/gtk/gtkwidgetprivate.h b/gtk/gtkwidgetprivate.h
index 9dfec658e2..7d298c6471 100644
--- a/gtk/gtkwidgetprivate.h
+++ b/gtk/gtkwidgetprivate.h
@@ -29,12 +29,13 @@
 
 G_BEGIN_DECLS
 
-/* With GtkWidget, a widget may be requested
- * its width for 2 or maximum 3 heights in one resize
- * (Note this define is limited by the bitfield sizes
- * defined on the SizeRequestCache structure).
+/* Cache as many ranges of height-for-width
+ * (or width-for-height) as can be rational
+ * for a said widget to have, if a label can
+ * only wrap to 3 lines, only 3 caches will
+ * ever be allocated for it.
  */
-#define GTK_SIZE_REQUEST_CACHED_SIZES   (2)
+#define GTK_SIZE_REQUEST_CACHED_SIZES   (5)
 
 typedef struct {
   gint minimum_size;
@@ -43,26 +44,24 @@ typedef struct {
 
 typedef struct
 {
-  /* the size this request is for */
-  gint       for_size;
+  gint       lower_for_size; /* The minimum for_size with the same result */
+  gint       upper_for_size; /* The maximum for_size with the same result */
   CachedSize cached_size;
 } SizeRequest;
 
 typedef struct {
-  SizeRequest widths[GTK_SIZE_REQUEST_CACHED_SIZES];
-  SizeRequest heights[GTK_SIZE_REQUEST_CACHED_SIZES];
-
-  guint       cached_widths      : 2;
-  guint       cached_heights     : 2;
-  guint       last_cached_width  : 2;
-  guint       last_cached_height : 2;
-} ContextualSizes;
-
-typedef struct {
-  ContextualSizes *sizes;
-
-  CachedSize cached_width;
-  CachedSize cached_height;
+  SizeRequest **widths;
+  SizeRequest **heights;
+
+  CachedSize  cached_width;
+  CachedSize  cached_height;
+
+  guint       cached_widths      : 3;
+  guint       cached_heights     : 3;
+  guint       last_cached_width  : 3;
+  guint       last_cached_height : 3;
+  guint       cached_base_width  : 1;
+  guint       cached_base_height : 1;
 } SizeRequestCache;
 
 void         _gtk_widget_set_visible_flag   (GtkWidget *widget,
@@ -114,6 +113,7 @@ gboolean _gtk_widget_get_translation_to_window (GtkWidget      *widget,
                                                 GdkWindow      *window,
                                                 int            *x,
                                                 int            *y);
+void     _gtk_widget_free_cached_sizes (GtkWidget *widget);
 
 G_END_DECLS