View Full Version : QMdiArea slow resize of child windows

9th June 2010, 21:11

I'm porting my app from Qt 3.3 to Qt 4.6. My app has a MDI area as a main window. In the past I have used QWorkspace but that is no longer available and I don't want to use the Q3 compatibility classes. So I switched to QMdiArea since that seems to be the successor of QWorkspace. When I resize a subwindow the resize operation is very slow and it looks ugly (all kind of distortions while resizing, the scrollbars move outsize the child window before the child gets redrawn). I know that I could turn on the rubberband resize mode but I want the feedback for the user (the subwindow contains an edit control). I know it is not the widget (edit control) that is the main widget of the subWindow since I can resize it fine when it is hosted in a dialog window. However, when I delete all text from the edit contol (TPlainTextEdit) it does seem to update ok...

You can test this by using the mdi applications in the example folder. Choose a moderate size file to open a child window and resize.

I have been running this on Windows 7.

My old app running under Qt 3.3 has no such performance issues. Any suggestions on how to speed this up?