From: Chris Cannam <cannam@al...> - 2004-06-29 14:44:32
On Monday 28 Jun 2004 4:11 pm, Guillaume Laurent wrote:
[quoting from Achim Spangler on kde-devel]
> I tried to control the double buffering with
> QCanvas::setDoubleBuffering( bool ) based on the hide and show
> events of the QCanvasView class
Interesting. The principle here seems to be that QCanvas
double-buffering takes up extra memory (as you might expect) and that
that memory is simply wasted if the canvas is not actually visible at
the time. That's no surprise either, I guess.
We never actually set double-buffering explicitly on any of our
canvases, I think, but it appears from the Qt documentation to be on
by default. I just tried switching it off for the notation canvas
and it made no visible difference to either speed (on my faster
machine) or memory usage. I don't quite understand that, at least as
regards memory usage.
Anyway -- since we don't routinely expect to have large numbers of
hidden canvases around, we probably don't need the fix discussed
here, although I guess it wouldn't hurt. The more obvious question
for me is whether we need to use QCanvas double buffering at all.