textview: add undo/redo support to GtkTextView

This builds upon the GtkTextHistory helper to provide undo and redo support
for the GtkTextView widget and GtkTextBuffer object.

You can undo/redo using familiar shortcuts such as Primary+Z,
Primary+Shift+Z, ad Primary+Y.

Developers that wish to disable undo, should set the
GtkTextBuffer:enable-undo property to FALSE.

You can wrap irreversible actions
gtk_text_buffer_begin_irreversible_action() and
gtk_text_buffer_end_irreversible_action(). This will cause the undo stack
to drop all undo/redo actions and the changes made between them will be
the "initial state" of the buffer.

Calling gtk_text_buffer_set_text() will do this automatically for you.

1 files changed, 2 insertions, 0 deletions

diff --git a/gtk/gtktextprivate.h b/gtk/gtktextprivate.h
index daeed71bce..500389824d 100644
--- a/gtk/gtktextprivate.h
+++ b/gtk/gtktextprivate.h
@@ -85,6 +85,8 @@ struct _GtkTextClass
   void (* paste_clipboard)    (GtkText         *self);
   void (* toggle_overwrite)   (GtkText         *self);
   void (* insert_emoji)       (GtkText         *self);
+  void (* undo)               (GtkText         *self);
+  void (* redo)               (GtkText         *self);
 };
 
 char *              gtk_text_get_display_text   (GtkText    *entry,