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  1. Qt
  2. QTBUG-103464

Raster paint engine choosing wrong transformation path

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    Details

    • Type: Bug
    • Status: Reported
    • Priority: P2: Important
    • Resolution: Unresolved
    • Affects Version/s: 6.2, 6.3
    • Fix Version/s: None
    • Component/s: GUI: Painting
    • Labels:
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      Description

      QRasterPaintEngine::drawImage() checks a number of factors to compute "exceedsPrecision", a flag to decide whether it can use the faster scale/transform functions. However, it will sometimes get it wrong, ref. the linked bug(s).
      The decision logic seems to be a bit ad hoc; it is not clear what the actual limits of the underlying fast functions are. Also:

      • The dimensions of "r" are checked, but not "sr" (source rect), even that is also passed
      • The amount of scaling in s->matrix is checked, but not the implicit scaling from the target rect having a different size than the source
      • Not clear if the same limits should apply to simple scaling as to more general transform
      • upscaling is limited, but not downscaling.

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              Assignee:
              vgt Eirik Aavitsland
              Reporter:
              vgt Eirik Aavitsland
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                Updated:

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