Egon Schaal wrote: > Is there a way to found out the highest scaling factor for zooming up the > scene. If scaling is to big, the performance going down if there is a big > QPainterPath to draw. We found that 4.5 improved the situation a lot with regard to the scene, however before 4.5 came out we had already done 3 things.
1, In the Path paint event cache the path as a pixmap and output that. Whenever the path is changed you have to invalidate the pixmap of course but for resize operations its a smooth as a pixmap. The downside to this is that with our application we have a main view of the scene and thumbnail views, the thumbnails are zoomed out (15% of the original size) and loose quality due to them being pixmaps at heart. 2, Draw the path on the view as lots of little paths and then on mouse up join them as one big path and add it to the scene, which then gets the benefit of pixmap caching. Obviously you have to also remove the view path which you have just drawn. 3, Switched from Mingw GCC (v3.4) to visual studio on windows (linux was Ok but that was gcc 4.3). We are not sure we need all of these now that 4.5 has been improved, however we are not going to roll back working code just to see. Hope that helps. Regards Phil Hannent
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