textbtree: short-circuit visibility check when possible

If we have never seen a GtkTextTag in the GtkTextTagTable with the
invisible bit set, then we do not need to go through the process of
checking the accumulated tags.

Not using invisible tags is overwhelmingly the common case.

gtk/gtktextbtree.c

@@ -61,7 +61,7 @@
 #include "gtktextbufferprivate.h"
 #include "gtktexttag.h"
 #include "gtktexttagprivate.h"
-#include "gtktexttagtable.h"
+#include "gtktexttagtableprivate.h"
 #include "gtktextlayout.h"
 #include "gtktextiterprivate.h"
 #include "gtkdebug.h"
@@ -2492,6 +2492,13 @@ _gtk_text_btree_char_is_invisible (const GtkTextIter *iter)
 
   line = _gtk_text_iter_get_text_line (iter);
   tree = _gtk_text_iter_get_btree (iter);
+
+  /* Short-circuit if we've never seen a visibility tag within the
+   * tag table (meaning everything must be visible).
+   */
+  if G_LIKELY (!_gtk_text_tag_table_affects_visibility (tree->table))
+    return FALSE;
+
   byte_index = gtk_text_iter_get_line_index (iter);
 
   numTags = gtk_text_tag_table_get_size (tree->table);

gtk/gtktexttagtable.c

@@ -68,6 +68,8 @@ struct _GtkTextTagTablePrivate
   GSList     *buffers;
 
   gint anon_count;
+
+  guint seen_invisible : 1;
 };
 
 enum {
@@ -160,6 +162,22 @@ gtk_text_tag_table_init (GtkTextTagTable *table)
   table->priv->hash = g_hash_table_new (g_str_hash, g_str_equal);
 }
 
+static void
+check_visible (GtkTextTagTable *table,
+               GtkTextTag      *tag)
+{
+  if (table->priv->seen_invisible)
+    return;
+
+  if (tag->priv->invisible_set)
+    {
+      gboolean invisible;
+
+      g_object_get (tag, "invisible", &invisible, NULL);
+      table->priv->seen_invisible = invisible;
+    }
+}
+
 /**
  * gtk_text_tag_table_new:
  * 
@@ -281,6 +299,8 @@ gtk_text_tag_table_add (GtkTextTagTable *table,
   g_assert (size > 0);
   tag->priv->priority = size - 1;
 
+  check_visible (table, tag);
+
   g_signal_emit (table, signals[TAG_ADDED], 0, tag);
   return TRUE;
 }
@@ -470,5 +490,12 @@ _gtk_text_tag_table_tag_changed (GtkTextTagTable *table,
                                  GtkTextTag      *tag,
                                  gboolean         size_changed)
 {
+  check_visible (table, tag);
   g_signal_emit (table, signals[TAG_CHANGED], 0, tag, size_changed);
 }
+
+gboolean
+_gtk_text_tag_table_affects_visibility (GtkTextTagTable *table)
+{
+  return table->priv->seen_invisible;
+}

gtk/gtktexttagtableprivate.h

@@ -36,6 +36,7 @@ void _gtk_text_tag_table_remove_buffer (GtkTextTagTable *table,
 void     _gtk_text_tag_table_tag_changed        (GtkTextTagTable *table,
                                                  GtkTextTag      *tag,
                                                  gboolean         size_changed);
+gboolean _gtk_text_tag_table_affects_visibility (GtkTextTagTable *table);
 
 G_END_DECLS