This patch ports the Effects KCM to QQC2, which yields the following benefits:
- General performance enhancements of only using QQC2 rather than a mix of 1 and 2
- Some code simplification is possible
- Improves the appearance of the checkable menu items in the dropdown menu, fixing https://bugs.kde.org/show_bug.cgi?id=402701
- Improves the appearance when using a fractional scale factor, fixing https://bugs.kde.org/show_bug.cgi?id=396725
- Fixes the incorrect size when opened from kcmshell5
Along the way, two visual changes are introduced as a by-product of porting:
- The scrollbar is inline, so it overlaps some of the buttons in the content. This is somewhat undesirable, but adopting a Kirigami scrollview would fix this.
- The button that displays a dropdown menu no longer has a downward-pointing arrow to indicate as such. This is not my preference, but there's a benefit to being consistent, and eventually we could can change this in one place to impeove the appearance of buttons that display dropdown menus everywhere in one fell swoop.