Android: set logicalDpi based on DisplayMetrics.scaledDensity

The mathematically correct way would be to set logicalDPi to
160*scaledDensity, but then a 12 pt font would be gigantic. On
iOS, we use a factor of 72 to be compatible with the native APIs,
but that means that a 12 pt font is very small.

A factor of 100 means that desktop apps look reasonable by default.

Task-number: QTBUG-29674

Change-Id: I607f110150fb95685a6980b92f6f92f2b489f959
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

2 files changed, 7 insertions, 0 deletions

diff --git a/src/plugins/platforms/android/src/raster/qandroidplatformscreen.cpp b/src/plugins/platforms/android/src/raster/qandroidplatformscreen.cpp
index 2779d7cffd..409c833db3 100644
--- a/src/plugins/platforms/android/src/raster/qandroidplatformscreen.cpp
+++ b/src/plugins/platforms/android/src/raster/qandroidplatformscreen.cpp
@@ -69,3 +69,9 @@ QRegion QAndroidPlatformScreen::doRedraw()
     QtAndroid::flushImage(mGeometry.topLeft(), *mScreenImage, touched.boundingRect());
     return touched;
 }
+
+QDpi QAndroidPlatformScreen::logicalDpi() const
+{
+    qreal lDpi = QtAndroid::scaledDensity() * 100;
+    return QDpi(lDpi, lDpi);
+}
diff --git a/src/plugins/platforms/android/src/raster/qandroidplatformscreen.h b/src/plugins/platforms/android/src/raster/qandroidplatformscreen.h
index df08e43af4..cfd503d611 100644
--- a/src/plugins/platforms/android/src/raster/qandroidplatformscreen.h
+++ b/src/plugins/platforms/android/src/raster/qandroidplatformscreen.h
@@ -50,6 +50,7 @@ class QAndroidPlatformScreen: public QFbScreen
 public:
     QAndroidPlatformScreen();
     void topWindowChanged(QWindow *w);
+    QDpi logicalDpi() const;
 
 public slots:
     QRegion doRedraw();