[dolphin] [Bug 472208] New: 24bpp .ico thumbnails render incorrectly, ignoring their mask.

[John Chadwick]

https://bugs.kde.org/show_bug.cgi?id=472208

            Bug ID: 472208
           Summary: 24bpp .ico thumbnails render incorrectly, ignoring
                    their mask.
    Classification: Applications
           Product: dolphin
           Version: unspecified
          Platform: NixOS
                OS: Linux
            Status: REPORTED
          Severity: minor
          Priority: NOR
         Component: general
          Assignee: dolphin-bugs-null at kde.org
          Reporter: john at jchw.io
                CC: kfm-devel at kde.org
  Target Milestone: ---

Created attachment 160260
  --> https://bugs.kde.org/attachment.cgi?id=160260&action=edit
An ico file that demonstrates the problem, created by me. CC0 license. Rendered
correctly, it should display as a circle, but KDE displays it as a rectangle.

SUMMARY
Some Windows .ico files (handled by the windows image thumcreator in
kio-extras) render improperly in Dolphin and other areas of KDE that render
file thumbnails. 32bpp icons render using their alpha channel and ignore the
mask as expected, but 24bpp icon files do not use their mask as expected.

This is caused by QTBUG-113319, which was fixed in Qt6 dev (and cherrypicked
into the active Qt release branches.) Since release versions of KDE currently
use Qt 5, the fix would need to be cherry-picked into the KDE Qt fork in order
to solve the problem in KDE.  This issue only causes graphical artifacts, so it
may not be important enough to warrant a cherry-pick.

STEPS TO REPRODUCE
1. Simply try to view a thumbnail for a 24bpp .ico file with a mask.

OBSERVED RESULT
The mask is not respected: all pixels are opaque.

EXPECTED RESULT
Pixels should be opaque or transparent based on their respective mask bits.

SOFTWARE/OS VERSIONS
KDE Frameworks Version: 5.107.0
Qt Version: 5.15.9

ADDITIONAL INFORMATION

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