[gtk/wip/chergert/fix-textview-yrange-invalidation] linedisplaycache: improve invalidation with y_range

[Christian Hergert <chergert src gnome org>]

commit f6895d253e475b37bea65c857a0e6bd4a68cd26e
Author: Christian Hergert <chergert redhat com>
Date:   Fri Aug 7 12:25:06 2020 -0700

    linedisplaycache: improve invalidation with y_range
    
    When we invalidate a y_range using the common pattern of y==0 and
    old_height==new_height, we are generally invalidating the entire buffer.
    
    This short-circuits that case to just invalidate the buffer in a faster
    and more complete form. The problem here appears to be that we can't
    always calculate the ranges properly to invalidate because validation
    has not run far enough.

 gtk/gtktextlayout.c                  |  4 ++--
 gtk/gtktextlinedisplaycache.c        | 10 ++++++++--
 gtk/gtktextlinedisplaycacheprivate.h |  3 ++-
 3 files changed, 12 insertions(+), 5 deletions(-)
---
diff --git a/gtk/gtktextlayout.c b/gtk/gtktextlayout.c
index 78439277bf..3e77b52f6c 100644
--- a/gtk/gtktextlayout.c
+++ b/gtk/gtktextlayout.c
@@ -656,7 +656,7 @@ gtk_text_layout_changed (GtkTextLayout *layout,
                          int            new_height)
 {
   GtkTextLayoutPrivate *priv = GTK_TEXT_LAYOUT_GET_PRIVATE (layout);
-  gtk_text_line_display_cache_invalidate_y_range (priv->cache, layout, y, old_height, FALSE);
+  gtk_text_line_display_cache_invalidate_y_range (priv->cache, layout, y, old_height, new_height, FALSE);
   gtk_text_layout_emit_changed (layout, y, old_height, new_height);
 }
 
@@ -667,7 +667,7 @@ gtk_text_layout_cursors_changed (GtkTextLayout *layout,
                                  int            new_height)
 {
   GtkTextLayoutPrivate *priv = GTK_TEXT_LAYOUT_GET_PRIVATE (layout);
-  gtk_text_line_display_cache_invalidate_y_range (priv->cache, layout, y, old_height, TRUE);
+  gtk_text_line_display_cache_invalidate_y_range (priv->cache, layout, y, old_height, new_height, TRUE);
   gtk_text_layout_emit_changed (layout, y, old_height, new_height);
 }
 
diff --git a/gtk/gtktextlinedisplaycache.c b/gtk/gtktextlinedisplaycache.c
index 91ce0d98e4..31a2fb007a 100644
--- a/gtk/gtktextlinedisplaycache.c
+++ b/gtk/gtktextlinedisplaycache.c
@@ -642,7 +642,8 @@ find_iter_at_at_y (GtkTextLineDisplayCache *cache,
  * gtk_text_line_display_cache_invalidate_y_range:
  * @cache: a GtkTextLineDisplayCache
  * @y: the starting Y position
- * @old_height: the height to invalidate
+ * @old_height: the old height of the range
+ * @old_height: the new height to the range
  * @cursors_only: if only cursors should be invalidated
  *
  * Remove all GtkTextLineDisplay that fall into the range starting
@@ -653,6 +654,7 @@ gtk_text_line_display_cache_invalidate_y_range (GtkTextLineDisplayCache *cache,
                                                 GtkTextLayout           *layout,
                                                 int                      y,
                                                 int                      old_height,
+                                                int                      new_height,
                                                 gboolean                 cursors_only)
 {
   GSequenceIter *iter;
@@ -663,7 +665,11 @@ gtk_text_line_display_cache_invalidate_y_range (GtkTextLineDisplayCache *cache,
 
   STAT_INC (cache->inval_by_y_range);
 
-  if (y < 0)
+  /* A common pattern is to invalidate the whole buffer using y==0 and
+   * old_height==new_height. So special case that instead of walking through
+   * each display item one at a time.
+   */
+  if (y < 0 || (y == 0 && old_height == new_height))
     {
       gtk_text_line_display_cache_invalidate (cache);
       return;
diff --git a/gtk/gtktextlinedisplaycacheprivate.h b/gtk/gtktextlinedisplaycacheprivate.h
index ffbe67bd42..3102109248 100644
--- a/gtk/gtktextlinedisplaycacheprivate.h
+++ b/gtk/gtktextlinedisplaycacheprivate.h
@@ -51,7 +51,8 @@ void                     gtk_text_line_display_cache_invalidate_range   (GtkText
 void                     gtk_text_line_display_cache_invalidate_y_range (GtkTextLineDisplayCache *cache,
                                                                          GtkTextLayout           *layout,
                                                                          int                      y,
-                                                                         int                      height,
+                                                                         int                      old_height,
+                                                                         int                      new_height,
                                                                          gboolean                 
cursors_only);
 void                     gtk_text_line_display_cache_set_mru_size       (GtkTextLineDisplayCache *cache,
                                                                          guint                    mru_size);