[konsole] [Bug 406770] New: Recent anti-aliasing change is causing black lines on HiDPI displays

[Bo Simonsen]

https://bugs.kde.org/show_bug.cgi?id=406770

            Bug ID: 406770
           Summary: Recent anti-aliasing change is causing black lines on
                    HiDPI displays
           Product: konsole
           Version: master
          Platform: Other
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: general
          Assignee: konsole-devel at kde.org
          Reporter: bo at geekworld.dk
  Target Milestone: ---

Created attachment 119556
  --> https://bugs.kde.org/attachment.cgi?id=119556&action=edit
screenshot of mc after antialiasing change

SUMMARY

The commit ed5fa1f855a05ba82fe4f2f6d3ead803aa5eefdb introduced painter
antialiasing which added unwanted black lines in programs like mc, iptraf-ng,
etc, i.e. console applications with colored background when running with a
scale factor e.g. 1.5. I would suggest to only use antialiasing in the painter
when scaling is not activated until a real fix is there.

Commenting out TerminalDisplay.cpp:1262 fixes the problem (but reintroduces
#397985, so a real fix is needed), the line:

    paint.setRenderHint(QPainter::Antialiasing, _antialiasText);

STEPS TO REPRODUCE
1. Set scale to 1.5
2. Start konsole
3. Run mc

OBSERVED RESULT

Black lines under every row

EXPECTED RESULT

A clean look

SOFTWARE/OS VERSIONS
KDE Plasma Version: 5.12.8
KDE Frameworks Version: 5.55.0
Qt Version: 5.9.7

Konsole master gives the result in the screenshot

ADDITIONAL INFORMATION

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