Fix various cursor problems.

[ardour.git] / gtk2_ardour / cursor_context.h

diff --git a/gtk2_ardour/cursor_context.h b/gtk2_ardour/cursor_context.h
new file mode 100644 (file)
index 0000000..9ce0862
--- /dev/null
+++ b/gtk2_ardour/cursor_context.h
@@ -0,0 +1,75 @@
+/*
+    Copyright (C) 2014 Paul Davis
+    Author: David Robillard
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#ifndef __ardour_gtk_cursor_context_h__
+#define __ardour_gtk_cursor_context_h__
+
+#include <boost/shared_ptr.hpp>
+#include <gdkmm/cursor.h>
+
+class Editor;
+
+/**
+   A scoped handle for changing the editor mouse cursor.
+
+   This is a safe way to change the cursor that ensures it is only modified in
+   a strict stack-like fashion.  Whenever this handle goes out of scope, the
+   cursor is restored to the previous one.
+
+   This is not quite entirely fool-proof, there is one case to be careful of:
+   if a cursor context handle exists, to change it, you must first reset that
+   handle (destroying the context) then set it.  Assigning a new context to a
+   non-NULL handle will create the new context (pushing a cursor), then destroy
+   the old one, which would attempt to pop a non-top context which is an
+   error.  To account for this, when replacing a possibly existing context, use
+   set() which will automatically do the right thing.
+*/
+class CursorContext
+{
+public:
+       /** A smart handle for a cursor change context. */
+       typedef boost::shared_ptr<CursorContext> Handle;
+
+       ~CursorContext();
+
+       /** Change the editor cursor and return a cursor context handle.
+        *
+        * When the returned handle goes out of scope, the cursor will be reset to
+        * the previous value.
+        */
+       static Handle create(Editor& editor, Gdk::Cursor* cursor);
+
+       /** Change the editor cursor of an existing cursor context. */
+       void change(Gdk::Cursor* cursor);
+
+       /** Set a context handle to a new context.
+        *
+        * If the handle points to an existing context, it will first be reset
+        * before the new context is created.
+        */
+       static void set(Handle* handle, Editor& editor, Gdk::Cursor* cursor);
+
+private:
+       Editor&      _editor;
+       size_t       _index;
+
+       CursorContext(Editor& editor, Gdk::Cursor* cursor);
+};
+
+#endif /* __ardour_gtk_cursor_context_h__ */