Rendering performance problems on iMac with Retina 5K
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@mrjj @ShikiSuen there is a real performance problem not with QWidgets, but with QWidgets's macOS implementation. I'm dual booting macOS/Linux on a retina macbook, and all the QWidgets applications I use, QtCreator, Clementine, Wireshark, (and the ones I develop) are much more fluid and smooth under Linux than MacOS even though it's the same hardware and screen resolution.
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@jcelerier
What resolution was it ? -
If anyone's interested I did a pass through Xcode's performance tools and put the trace here :
as you can see, roughly 25% of the time is spent in CGContextDrawImage. This was with QtCreator, but I have similar findings when benchmarking my app.
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Super.
Hopefully a fix comes out of it if possible. -
I experience intolerably poor graphics performance on Macs with QtWidgets in the following constellation:
- Qt 5, any version - Qt 4 on the same hardware is fine.
- macOS 10.10 and up - 10.9 or older on the same hardware is fine.
- not limited to retina displays, though obviously worse on them.
This is becoming a major PITA as it means my cross-platform app remains stuck at Qt 4.8.6 / Quick 1.1 on macOS, vs. Qt 5.6 / Quick 2.3 everywhere else.
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To be precise, by Qt5 widgets being "fine" on macOS 10.9 or older I mean that the lag is "only" ~50ms, not seconds. I suspect (though can't test right now) that adding a GL widget (cf QTBUG-61384) might get me in the same 50ms ballpark on newer versions of macOS, but that's still too much for my software (a strobe tuner, which needs fast rendering).
@jcelerier Right on, the last Qt version with decent QWidgets rendering performance on macOS was 4.8 with the raster engine. Qt5 widgets have been unusable for real-time graphics on Macs from the start, and it hasn't gotten any better. @ShikiSuen Steinberg has my full sympathies, I know how it feels like.
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