The gtk_fixed widget was used as a reference to obtain a fixed font
and HeaderViewFont.
This is a mistake, because the gtk_fixed widget is a container for
other widgets with fixed geometries and no layouting.
This patch makes the default style being used for a fixed font and, as
a drive-by, the combo box as a reference for a header view font.
A monospace based css provider as explicitly added to the style
context, in case a fixed font is requested. The provider is removed
afterwards.
Task-number: QTBUG-112896
Pick-to: 6.5
Change-Id: I6bfb2ee9e7befdd2102bdcc6e53ced954a024034
Reviewed-by: Oliver Eftevaag <oliver.eftevaag@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
034a071bda