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  1. Qt
  2. QTBUG-66036

QTextLayout draw() rendering issues with "some" font sizes

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Details

    • Bug
    • Resolution: Unresolved
    • P2: Important
    • 5.12.0 Alpha
    • 5.10.0, 5.13.0
    • GUI: Painting
    • None
    • Can be reproduced with latest Qt on at least X11 and macOS (you just need to zoom in your text document, you surely will hit some font size that is bad)
    • macOS
    • 47904bb08aeb5dc63c78357aba6003460a65d4b3

    Description

      Different applications using the QTextLayout mechanism to render text have the same rendering glitches with some font sizes.

      You will get horizontal or vertical "non-filled" pixels in your textlines.

      E.g. If you have some "white" background and paint over text with some different background, you sometimes will get small "gaps" in the painted text.

      This happens e.g. on X11 or macOS.

      Example bug in Kate/KWrite (that uses QTextLayout directly without QTextDocument) can be seen here (horizontal lines, the same can happen vertically):

       

      https://bugs.kde.org/show_bug.cgi?id=379727

      https://bugsfiles.kde.org/attachment.cgi?id=105445

       

      Effect with QtCreator using 5.10.0 on macOS:

       

       

      Given two totally different code bases have the same issue (and QtCreator uses QTextDocument), I think this is some rendering issue in Qt.

      Attachments

        1. Bildschirmfoto 2018-01-27 um 16.50.19.png
          110 kB
          Christoph Cullmann
        2. Bildschirmfoto 2018-02-10 um 21.00.11.png
          37 kB
          Christoph Cullmann
        3. Bildschirmfoto 2018-02-10 um 21.00.19.png
          38 kB
          Christoph Cullmann
        4. kwrite_scale_1_2_qrect_clip.png
          321 kB
          Christoph Cullmann
        5. kwrite_scale_1_2_qrectF_clip.png
          320 kB
          Christoph Cullmann
        6. screenshot.png
          49 kB
          Christoph Cullmann
        7. vertical_white_lines.png
          119 kB
          Christoph Cullmann
        8. white_artifacts.png
          10 kB
          Christoph Cullmann
        For Gerrit Dashboard: QTBUG-66036
        # Subject Branch Project Status CR V

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            sletta Gunnar Sletta
            cullmann Christoph Cullmann
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            Dates

              Created:
              Updated:

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