Move QT_FONT_DPI to cross-platform code

This makes it possible to test the effects of setting
Qt::AA_HighDpiScaling/QT_AUTO_SCREEN_SCALE_FACTOR, with different DPI
values on all platforms.

This also makes it possible to access the actual DPI values reported
by the OS/WS via the QPlatformScreen API.

A drawback is that there is no single place to check the environment
variable; currently done in three places. This may be
further simplified later on.

Done-with: Friedemann Kleint <Friedemann.Kleint@qt.io>
Task-number: QTBUG-53022
Change-Id: Idd6463219d3ae58fe0ab72c17686cce2eb9dbadd
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/src/gui/kernel/qhighdpiscaling.cpp b/src/gui/kernel/qhighdpiscaling.cpp
index 7ffbfbe1e5..c8a2634929 100644
--- a/src/gui/kernel/qhighdpiscaling.cpp
+++ b/src/gui/kernel/qhighdpiscaling.cpp
@@ -276,7 +276,7 @@ qreal QHighDpiScaling::rawScaleFactor(const QPlatformScreen *screen)
         qreal platformPhysicalDpi = screen->screen()->physicalDotsPerInch();
         factor = qreal(platformPhysicalDpi) / qreal(platformBaseDpi.first);
     } else {
-        QDpi platformLogicalDpi = screen->logicalDpi();
+        const QDpi platformLogicalDpi = QPlatformScreen::overrideDpi(screen->logicalDpi());
         factor = qreal(platformLogicalDpi.first) / qreal(platformBaseDpi.first);
     }
 
@@ -629,7 +629,7 @@ QDpi QHighDpiScaling::logicalDpi(const QScreen *screen)
         return QDpi(96, 96);
 
     if (!m_usePixelDensity)
-        return screen->handle()->logicalDpi();
+        return QPlatformScreen::overrideDpi(screen->handle()->logicalDpi());
 
     const qreal scaleFactor = rawScaleFactor(screen->handle());
     const qreal roundedScaleFactor = roundScaleFactor(scaleFactor);