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>

1 files changed, 9 insertions, 2 deletions

diff --git a/src/plugins/platforms/android/src/androidjnimain.cpp b/src/plugins/platforms/android/src/androidjnimain.cpp
index ae94e75e34..36d95b0816 100644
--- a/src/plugins/platforms/android/src/androidjnimain.cpp
+++ b/src/plugins/platforms/android/src/androidjnimain.cpp
@@ -123,6 +123,7 @@ static QAndroidPlatformIntegration *m_androidPlatformIntegration = 0;
 
 static int m_desktopWidthPixels  = 0;
 static int m_desktopHeightPixels = 0;
+static double m_scaledDensity = 0;
 
 static volatile bool m_pauseApplication;
 
@@ -287,6 +288,11 @@ namespace QtAndroid
         return m_desktopHeightPixels;
     }
 
+    double scaledDensity()
+    {
+        return m_scaledDensity;
+    }
+
     JavaVM *javaVM()
     {
         return m_javaVM;
@@ -623,10 +629,11 @@ static void destroySurface(JNIEnv *env, jobject /*thiz*/)
 static void setDisplayMetrics(JNIEnv */*env*/, jclass /*clazz*/,
                             jint /*widthPixels*/, jint /*heightPixels*/,
                             jint desktopWidthPixels, jint desktopHeightPixels,
-                            jdouble xdpi, jdouble ydpi)
+                            jdouble xdpi, jdouble ydpi, jdouble scaledDensity)
 {
     m_desktopWidthPixels = desktopWidthPixels;
     m_desktopHeightPixels = desktopHeightPixels;
+    m_scaledDensity = scaledDensity;
 
     if (!m_androidPlatformIntegration) {
         QAndroidPlatformIntegration::setDefaultDisplayMetrics(desktopWidthPixels,desktopHeightPixels,
@@ -687,7 +694,7 @@ static JNINativeMethod methods[] = {
     {"resumeQtApp", "()V", (void *)resumeQtApp},
     {"quitQtAndroidPlugin", "()V", (void *)quitQtAndroidPlugin},
     {"terminateQt", "()V", (void *)terminateQt},
-    {"setDisplayMetrics", "(IIIIDD)V", (void *)setDisplayMetrics},
+    {"setDisplayMetrics", "(IIIIDDD)V", (void *)setDisplayMetrics},
     {"setSurface", "(Ljava/lang/Object;)V", (void *)setSurface},
     {"destroySurface", "()V", (void *)destroySurface},
     {"lockSurface", "()V", (void *)lockSurface},