> On Oct 7, 2017, at 8:00 PM, Christian Gagneraud <chg...@gmail.com> wrote: > > On 8 October 2017 at 06:27, Patrick Stinson <patrickk...@gmail.com> wrote: >> Hmm. Actually, I think that the elastic node example is implemented in the >> same way as my app. Because of the delayed response of the “elasticity” in >> the algorithm it is not possible to demonstrate a solution to my problem >> even if it solved it. >> >> Like the elastic node example, I am implementing QGraphicsItem::itemChange >> for the node listening for QGraphicsItem::ItemPositionHasChanged, and then >> updating the edges’s geometry just after calling ::prepareGeometryChange. >> This queues an update for the next paint buffer, which is what causes my >> problem. > > If you can notice the time lag b/w the 2 paint events, it means that > something is slow. Slow enough to cause a 20+ ms delay. > So maybe your problem is elsewhere. Do you have this problem even > without the opengl view?
What I mean is that this is visible if I move the mouse one pixel, or event more visible (and quite annoying) if I nudge the node (say, 10 pixels at a time) with the arrow keys. > > If i'm not wrong, although the paint() on the edge item is not called > within your mouse event of the node. the edge should be repainted > right after the mouse event has finished, which should be a very short > time period. > > But maybe you’re talking about "paint buffer" in the OpenGL pipeline? I think you had me right. I (sadly) don’t know anything about OpenGL! > >> What I am wondering is if it is possible to implement painting in a >> synchronous way, where all paint events which result from a single mouse >> event are done in the same buffer frame. > > Or maybe your python code is too slow to make the 2 paint event fits > in a single buffer frame timeline. > > Chris > >> >> Make sense? >> >> >> On Oct 7, 2017, at 1:01 AM, Christian Gagneraud <chg...@gmail.com> wrote: >> >> On 7 October 2017 at 16:08, Patrick Stinson <patrickk...@gmail.com> wrote: >> >> Hi there! >> >> I have a graph-ish diagram app where dragging some objects (like nodes) >> necessitates dragging other objects (like connecting edges). However, if I >> update an edge from the mouse event or ItemChanged(position) event then the >> edge isn’t painted until the next paint event. At times, this is quite >> obvious for example when nudging a node with an arrow key and the node is >> going in one direction and edge goes in the other direction for one frame >> because it is one buffer behind. >> >> Any thoughts on synchronous painting? >> >> >> Have you check the "Elastic node" example? It does exactly what >> you're describing. And last time i tried it, it worked very well, no >> painting artifact. >> How is your "update" done exactly? >> >> Chris >> >> >> Thank you >> -Patrick >> _______________________________________________ >> Interest mailing list >> Interest@qt-project.org >> http://lists.qt-project.org/mailman/listinfo/interest >> >>
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