Uploaded image for project: 'Qt'
  1. Qt
  2. QTBUG-78964

fillRect + Anti-Aliasing + hi-dpi Scaling => missing filled pixels

    XMLWordPrintable

    Details

    • Type: Bug
    • Status: Closed
    • Priority: P1: Critical
    • Resolution: Invalid
    • Affects Version/s: 5.13.1
    • Fix Version/s: None
    • Component/s: GUI: Painting
    • Labels:
      None
    • Platform/s:
      Linux/X11

      Description

      fillRect misses to fill one pixel high lines at start or end of area if the scaling is fractional.

      This even happens if you e.g. just fill simple x * 14 pixel regions, you will often have 1 pixel empty lines in-between such groups.

      see https://bugreports.qt.io/browse/QTBUG-66036?focusedCommentId=479175&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-479175

      Turning off anti-aliasing rectifies this issue.

      This leads to strange rendering artifacts in many applications, like linked above in KWrite.
      There I worked around this by turning AA off before I call fillRect, thought this is not expected.
      (and seems only to happen in combination with some QT_SCALE_FACTOR or otherwise triggered fractional hi-dpi scaling)

        Attachments

        No reviews matched the request. Check your Options in the drop-down menu of this sections header.

          Activity

            People

            • Assignee:
              vgt Eirik Aavitsland
              Reporter:
              cullmann Christoph Cullmann
            • Votes:
              3 Vote for this issue
              Watchers:
              6 Start watching this issue

              Dates

              • Created:
                Updated:
                Resolved:

                Gerrit Reviews

                There are no open Gerrit changes