> So using QGIS to convert my .shp files to .svg, and then loading the result > in a > QGraphicsSVGItem works like a charm - thanks! The only drawback I’m seeing > is zooming performance. It *looks* good, but is a tad sluggish. When using > QGIS, I noticed that it was compiled against Qt as well, but when they zoom, > the actual image redraw is delayed until the zoom is complete. That is, when > zooming in, things get pixelated until you pause, whereupon they are re-drawn > correctly. When zooming out, areas that were outside the window remain empty > until you pause, at which point they are drawn. The end result is that things > look > worse when zooming, but zoom performance is lag-free. Is this behavior easily > obtainable, such as through a setting on the QGraphicsSVGItem or perhaps the > QGraphicsView, or is QGIS doing something completely different, such that I > would have to do a lot of re-implementation to accomplish said effect?
It sounds like their strategy is something like this: when the initial image is loaded (or when the user stops zooming), they show that image and they also make a raster version of it. Then as the user requests a zoom, they instantly rescale/resize/crop the raster image to present the pixelated (on zoom in) or the empty areas (on zoom out) versions. At the same time they start a timer, if the user continues to zoom before that timer expires they just keep working with the raster image and keep resetting the timer. Only once the timer expires (which is when the user stops zooming) do they actual do the real zoom and redraw the scene at the new desired resolution. This should give you faster speed, while not having you go through all the work of the intermediate zoom levels - you'll only have to generate the final zoomed scene for each zoom sequence. Sean This message has been scanned for malware by Forcepoint. www.forcepoint.com _______________________________________________ Interest mailing list Interest@qt-project.org https://lists.qt-project.org/listinfo/interest