View Full Version : Turn off backing store

7th February 2007, 18:11
I am helping to develop an OpenGl plotting system with ToddAtWSU. The plotting system works well, except when another window covers the plot, however briefly. When covered and uncovered, the drawing slows down to a halt and hangs the system. Someone I work with mentioned a "backing store" and trying to disable it. Looking through the forums, there is mention that "...I think backing store can be disabled" but not concrete yes/no. Is this possible in Qt4.1.4+? If so, how do you do it? We are interested in if this solves our problem in the drawing.

Mucho Thanks in advance

7th February 2007, 18:51
AFAIK OpenGL backend doesn't use a backing store.

7th February 2007, 18:58
AFAIK OpenGL backend doesn't use a backing store.

Does anything in Qt other than QPainter use a backing store? For instance, the QWidgets that make up the UI? The slowdown only occurs when another window (print dialog, open dialog etc) covers up any portion of the plot.

7th February 2007, 20:04
QPainter is only an interface. It is QPaintDevice/QPaintEngine that is or is not backstore enabled (at least I think so).

Try to see if default Qt examples that use OpenGL experience simmilar slowdowns. If not, then the problem is probably in your code.

8th February 2007, 19:01
AFAIK, only QPainters targeted to a QWidget* use the backing store. On Mac and MSWin, you can't disable this, despite the somewhat contradictory documentation. (Some places say you can, some say you can't.) I believe in X, you can disable the backing store.

*But, as others have mentioned, GL does not use the backing store, even if it's a 'widget'.