This makes no sense.
You can't round it to icon sizes *after* scaling, it means the shorter size is always just wrong.

If we do merge this patch, you want:

m_iconPixmap.size().scaled(QSize(Units.roundtoIconSize(actualContainerSize.width), Units.roundToIconSize(actualContainerSize.height)

You're using references a lot in a few patches that don't make any sense.

paintedSize returns a new QSize object; you're keeping a reference to a value that would just be immediately discarded. This doesn't result in an optimisation but instead doing something that would crash if it wasn't for a magic C++ feature where it lengthens the lifespan of the object.

the final size should be:
the *biggest* between width and height should be rounded to icon size
the other dimension should be scaled accordingly keeping the same proportions, so for example, if the original is
200*100 pixels, and you paint of a 32x32 icon canvas, the final image should be 32x16 (possibly painted centered)

Copying a better explanation of the bug here from on IRC:

‎[13:09] ‎<‎d_ed‎>‎ kbroulik: assuming the standard icon sizes are 16,32,48 if I have an icon that is 48x45 your paintedSize will return 48x32

‎[13:12] ‎<‎d_ed‎>‎and your unit test currently only passes because roundToIcon size has a code path of if size > KIconLoader::SizeHuge return size