Disable low-priority rendering after text input: it did not work correctly and caused WPF to render twice per character entered into AvalonEdit.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@5528 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Rendering/TextView.cs

@@ -136,9 +136,12 @@ namespace ICSharpCode.AvalonEdit.Rendering
 		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
 		{
 			if (managerType == typeof(TextDocumentWeakEventManager.Changing)) {
-				// put redraw into background so that other input events can be handled before the redraw
+				// TODO: put redraw into background so that other input events can be handled before the redraw.
+				// Unfortunately the "easy" approach (just use DispatcherPriority.Background) here makes the editor twice as slow because
+				// the caret position change forces an immediate redraw, and the text input then forces a background redraw.
+				// When fixing this, make sure performance on the SharpDevelop "type text in C# comment" stress test doesn't get significantly worse.
 				DocumentChangeEventArgs change = (DocumentChangeEventArgs)e;
-				Redraw(change.Offset, change.RemovalLength, DispatcherPriority.Background);
+				Redraw(change.Offset, change.RemovalLength, DispatcherPriority.Normal);
 				return true;
 			} else if (managerType == typeof(PropertyChangedWeakEventManager)) {
 				OnOptionChanged((PropertyChangedEventArgs)e);