<![CDATA[In which cases does QGraphicsScene::render not work?]]>And again, good day to everyone!
Can anyone tell under what conditions the procedure scene->render(...) won't do anything?
I observe a number of situations when, with a completely correct "input", the rendering of the specified area simply does not occur, although there are objects to draw (thousands of polygons) (and the execution time of the render() operation takes 0.0 ms).
If no one has any ideas offhand, then I will give a clipping from the code demonstrating the problem.
Thank you in advance for any help!

]]>https://forum.qt.io/topic/139705/in-which-cases-does-qgraphicsscene-render-not-workRSS for NodeWed, 23 Sep 2026 03:34:27 GMTFri, 30 Sep 2022 17:00:24 GMT60<![CDATA[Reply to In which cases does QGraphicsScene::render not work? on Fri, 30 Sep 2022 22:47:56 GMT]]>@JonB , yes, indeed, the problem was with the boundingRect() function, which I forgot to update when installing the "crutch". Now everything works correctly :) Thank you for the tip!

]]>https://forum.qt.io/post/730918https://forum.qt.io/post/730918Fri, 30 Sep 2022 22:47:56 GMT<![CDATA[Reply to In which cases does QGraphicsScene::render not work? on Fri, 30 Sep 2022 22:46:09 GMT]]>@SGaist , look, while I was making a cropped copy of the program, I solved my original problem xD
However, the solution is a "crutch" that I would like not to use.
At the moment, the problem is this - when zooming the map, there is a moment when the rendering time of a new map section begins to take ten times longer than before. I can't understand why this is happening and hope for your help :)
Google disc program archive
P.S. I use Qt 5.12.

]]>https://forum.qt.io/post/730917https://forum.qt.io/post/730917Fri, 30 Sep 2022 22:46:09 GMT<![CDATA[Reply to In which cases does QGraphicsScene::render not work? on Fri, 30 Sep 2022 18:28:18 GMT]]>@RoApPr
Fair enough. Are you able to test whether if you do not pass in any rectangles (so whole scene) these objects do show? Then we know it seems to be a source rectangle issue.

]]>https://forum.qt.io/post/730891https://forum.qt.io/post/730891Fri, 30 Sep 2022 18:28:18 GMT<![CDATA[Reply to In which cases does QGraphicsScene::render not work? on Fri, 30 Sep 2022 18:27:38 GMT]]>Hi,

Can you provide a minimal compilable example that shows that issue ?

]]>https://forum.qt.io/post/730890https://forum.qt.io/post/730890Fri, 30 Sep 2022 18:27:38 GMT<![CDATA[Reply to In which cases does QGraphicsScene::render not work? on Fri, 30 Sep 2022 18:25:57 GMT]]>@JonB said in In which cases does QGraphicsScene::render not work?:

If you are, you are quite certain they are correct?

Yes, I use them, and I am absolutely sure of their correctness. BUT, even if this is not the case, I manually checked some of their correct values, at which rendering also does not occur.

]]>https://forum.qt.io/post/730888https://forum.qt.io/post/730888Fri, 30 Sep 2022 18:25:57 GMT<![CDATA[Reply to In which cases does QGraphicsScene::render not work? on Fri, 30 Sep 2022 17:40:22 GMT]]>@RoApPr said in In which cases does QGraphicsScene::render not work?:

with a completely correct "input"

Are you passing target or source rectangles? If you are, you are quite certain they are correct? That would be my first thought.

]]>https://forum.qt.io/post/730872https://forum.qt.io/post/730872Fri, 30 Sep 2022 17:40:22 GMT