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  1. Qt
  2. QTBUG-71162

Layer-backed backingstore flush copies whole backingstore on each flush

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Details

    • macOS
    • 77a4915bf900aac0c96260018c0a4ccfbdd7c094 (qt/qtbase/5.12)
    • Bug Fixing Week Q2/2020

    Description

      Painting on a layer-backed window on macOS (which is apparently unavoidable now when building agains the 10.14 SDK?) performs poorly because of QImage::detach copying the image. This is related to QTBUG-63559. The commit message for that issue indicates that it isn't expected to be fixed for layer-backed windows.

      Is there any way to avoid the copy or disable the layer-backed backing store? I tried setting QT_MAC_WANTS_LAYER=0 without success.

      Attachments

        1. detach-in-flush.png
          225 kB
          Jason Haslam
        2. layer-backed.png
          199 kB
          Jason Haslam
        3. layer-backed-detach.diff
          1 kB
          Jason Haslam
        4. non-layer-backed.png
          245 kB
          Jason Haslam
        5. test.cpp
          0.7 kB
          Jason Haslam

        Issue Links

          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-73073 Animation uses CPU time too much

          • Not Evaluated - Not yet evaluated/prioritized
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. QTBUG-70800 When using QT_MAC_WANTS_LAYER then the CPU usage can be really high in comparison to without it

          • P2: Important - Urgent, should be fixed, but will not stop the release.
          • Closed

          Activity

            People

              vestbo Tor Arne Vestbø
              jasonhaslam Jason Haslam
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              Dates

                Created:
                Updated:
                Resolved: