D11244: Fix text scaling with non-integer scale factors when PLASMA_USE_QT_SCALING=1 is set

[Nathaniel Graham]

ngraham created this revision.
ngraham added reviewers: Plasma, davidedmundson.
Restricted Application added a project: Frameworks.
Restricted Application added a subscriber: Frameworks.
ngraham requested review of this revision.

REVISION SUMMARY
  When `PLASMA_USE_QT_SCALING=1` is set, Plasma uses native Qt scaling. This works fine for integer scale factors, and fixes a lot of bugs (see Bug 356446 <https://bugs.kde.org/show_bug.cgi?id=356446> but it introduces a new one: with non-integer scale factors, text becomes blurry and pixellated, because NativeRenderins is used, and PlasmaComponents QML objects don't implement the fix that QQC2-desktop-style does to force the use of Qt font rendering for non-integer scale factors. This patch fixes that, and gets us one step closer to being able to use Qt scaling in Plasmashell.
  
  There is no effect when `PLASMA_USE_QT_SCALING=1` is not being used.
  
  FIXED-IN 5.13
  BUG: 391691

TEST PLAN
  Before: `PLASMA_USE_QT_SCALING=1` set, 1.2 scale factor: Plasma text looks awful
  
  After: `PLASMA_USE_QT_SCALING=1` set, 1.2 scale factor: Plasma text looks amazing!
  
  Witout both `PLASMA_USE_QT_SCALING=1` and a non-integer scale factor set, there is no visual change.

REPOSITORY
  R242 Plasma Framework (Library)

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D11244

AFFECTED FILES
  examples/applets/testtheme/contents/ui/FontGizmo.qml
  src/declarativeimports/plasmacomponents/qml/Label.qml
  src/declarativeimports/plasmacomponents/qml/private/DualStateButton.qml
  src/declarativeimports/plasmacomponents3/ComboBox.qml
  src/declarativeimports/plasmacomponents3/Label.qml
  src/declarativeimports/plasmacomponents3/TextArea.qml
  src/declarativeimports/plasmacomponents3/TextField.qml
  src/declarativeimports/plasmastyle/ComboBoxStyle.qml
  src/declarativeimports/plasmastyle/SpinBoxStyle.qml
  src/declarativeimports/plasmastyle/TextAreaStyle.qml
  src/declarativeimports/plasmastyle/TextFieldStyle.qml

To: ngraham, #plasma, davidedmundson
Cc: #frameworks, michaelh
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