On 7 April 2017 at 15:02, Patrick Stinson <patrickk...@gmail.com> wrote: > >> On Apr 6, 2017, at 7:57 PM, Ch'Gans <chg...@gna.org> wrote: >> >> On 7 April 2017 at 14:38, Patrick Stinson <patrickk...@gmail.com> wrote: >>> I am implementing a pan and zoom on pinch via raw touch events and am >>> finding setTransform() to be very slow, even with an empty scene. The touch >>> events are backed up in a queue by slow synchronous calls to >>> QGraphicsView.setTransform(). >> >> If it's slow with an empty scene, then you have a problem that has >> nothing to do with QTransform. Maybe you have a cascade of events that >> bounce on each other until it stabilise... >> Maybe your synchronous calls are too frequent. I would advise to use >> the animation framework to do this sort of things. > > This is possible. I will check further. > >> >> Whats your environment, which HW, which OS, which Qt, … > > I am using Qt-5.8.1 and PyQt-5.8.1, latest sierra with latest MacBook pro > >> >>> >>> Without stripping down my code into a runnable example, is setTransform >>> considered to be too slow for 60Hz frame-rate updates from touch events? If >>> so, is there a better way to smoothly zoom and pan the graphics view? >> >> Use the animation framework. no need for a queue mechanism, should >> work without any problems unless you hardware is not powerful enough. >> > > How would one animate the transform without a "transform" property? Or am I > missing something? (I’ve been away from qt for a while - since before the > animation framework) >
I didn't say w/o a "transform" property, i said w/o a queue. My point is that using the animation framework will likely be easier and gives smoother result than using QTimer and a "command queue". BTW, you cannot animate the "transform" property without providing your own interpolation function. But you can work around that by animating scale factor and translation. PS: I've just found this https://wiki.qt.io/Smooth_Zoom_In_QGraphicsView, haven't tried it, but this might help you in your quest. Chris > >> Chris >> >>> >>> Thanks! >>> -P >>> _______________________________________________ >>> Interest mailing list >>> Interest@qt-project.org >>> http://lists.qt-project.org/mailman/listinfo/interest > _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
