Hi All, For some time I've been noticing that QGIS 3.0 on MacOSX has sluggish canvas redraw speeds. When comparing between QGIS 2.18 and 3.0 I see ~4x more CPU activity in 3.0 when performing the same set of operations on the same dataset.
My test case was using a single raster VRT with overviews, and zooming in and panning around the map cavnas for 20 sec. On average each time I tested this case the total used CPU time for 2.18 was about 6 secs, but in 3.0dev-64369f8099 (complied against QT 5.10.0 with homebrew) I get total CPU time of 25 secs. In QGIS 3.0 most of the time the application is using 100% CPU (one core) and spikes to about 180-200% CPU when the canvas redraws are performed. When using a profiler it seems much of the time is taken up in QImage::copy(QRect const&) within two seperate, but equivalent, call subtrees. See [1] for more info. Is anyone else seeing slow map canvas performance in QGIS 3.0 on MacOSX? Cheers, Jeremy [1] - https://imgur.com/a/ZSRTf
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