> Sent: Thursday, December 17, 2015 at 11:45 AM > From: "william.croc...@analog.com" <william.croc...@analog.com> > To: No recipient address > Cc: "interest@qt-project.org" <interest@qt-project.org> > Subject: Re: [Interest] Unnecessary repaints. > > On 12/17/2015 11:16 AM, Jason H wrote: > > > >> > >> My very first Qt app is large and a little sloppy in > >> that the QWidget::update() function is being called > >> *someplace* where it should not, This is causing > >> unnecessary repaints. > >> > >> Is there one place I can put a break to find the calls > >> which actually cause a repaint (and not the calls > >> which are made when a repaint is already pending). > >> > >> Or, can you recommend a better way to diagnose > >> this problem. (The whole thing needs to be rewritten > >> now that I am older and wiser, but not just yet.) > > > > Why do you think they are unnecessary? > > Which update() is being called? There's like 4 overloads. Also, realize > > that Qt will optimize out unneeded updates, or combine multiple into one. I > > find that Qt is very good about not doing more than needed. It's better to > > track the paintEvent()s. > > > > I do not think there is a Qt issue here. > I'm sure it is me that is calling update when I should not. > > I know they are unnecessary because my app responds with multiple > screen refreshes (paints) from a single user action. And for me those > paints can be expensive.
Did you write a widget that calls update()? I'm not sure I understand your concern. update() should only be called when a redraw is needed. This is primarily done to reflect new data, or occasionally because something obscured the widget, which was not stored on a double buffer, and it needs to be redrawn. See also invalidate(). What single user action is happening? _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
