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>

8 files changed, 38 insertions, 9 deletions

diff --git a/src/android/jar/src/org/qtproject/qt5/android/QtActivityDelegate.java b/src/android/jar/src/org/qtproject/qt5/android/QtActivityDelegate.java
index b6e6e3397e..c1fe8920f5 100644
--- a/src/android/jar/src/org/qtproject/qt5/android/QtActivityDelegate.java
+++ b/src/android/jar/src/org/qtproject/qt5/android/QtActivityDelegate.java
@@ -476,7 +476,7 @@ public class QtActivityDelegate
             m_activity.getWindowManager().getDefaultDisplay().getMetrics(metrics);
             QtNative.setApplicationDisplayMetrics(metrics.widthPixels, metrics.heightPixels,
                                                   metrics.widthPixels, metrics.heightPixels,
-                                                  metrics.xdpi, metrics.ydpi);
+                                                  metrics.xdpi, metrics.ydpi, metrics.scaledDensity);
         }
         m_layout = new QtLayout(m_activity);
         m_surface = new QtSurface(m_activity, 0);
diff --git a/src/android/jar/src/org/qtproject/qt5/android/QtNative.java b/src/android/jar/src/org/qtproject/qt5/android/QtNative.java
index 7cb3fdff45..4586ae2002 100644
--- a/src/android/jar/src/org/qtproject/qt5/android/QtNative.java
+++ b/src/android/jar/src/org/qtproject/qt5/android/QtNative.java
@@ -72,6 +72,7 @@ public class QtNative
     private static int m_displayMetricsDesktopHeightPixels = 0;
     private static double m_displayMetricsXDpi = .0;
     private static double m_displayMetricsYDpi = .0;
+    private static double m_displayMetricsScaledDensity = 1.0;
     private static int m_oldx, m_oldy;
     private static final int m_moveThreshold = 0;
     private static ClipboardManager m_clipboardManager = null;
@@ -195,7 +196,8 @@ public class QtNative
                               m_displayMetricsDesktopWidthPixels,
                               m_displayMetricsDesktopHeightPixels,
                               m_displayMetricsXDpi,
-                              m_displayMetricsYDpi);
+                              m_displayMetricsYDpi,
+                              m_displayMetricsScaledDensity);
             if (params.length() > 0)
                 params = "\t" + params;
             startQtApplication(f.getAbsolutePath() + "\t" + params, environment);
@@ -209,7 +211,8 @@ public class QtNative
                                                     int desktopWidthPixels,
                                                     int desktopHeightPixels,
                                                     double XDpi,
-                                                    double YDpi)
+                                                    double YDpi,
+                                                    double scaledDensity)
     {
         /* Fix buggy dpi report */
         if (XDpi < android.util.DisplayMetrics.DENSITY_LOW)
@@ -224,7 +227,8 @@ public class QtNative
                                   desktopWidthPixels,
                                   desktopHeightPixels,
                                   XDpi,
-                                  YDpi);
+                                  YDpi,
+                                  scaledDensity);
             } else {
                 m_displayMetricsScreenWidthPixels = screenWidthPixels;
                 m_displayMetricsScreenHeightPixels = screenHeightPixels;
@@ -232,6 +236,7 @@ public class QtNative
                 m_displayMetricsDesktopHeightPixels = desktopHeightPixels;
                 m_displayMetricsXDpi = XDpi;
                 m_displayMetricsYDpi = YDpi;
+                m_displayMetricsScaledDensity = scaledDensity;
             }
         }
     }
@@ -535,7 +540,8 @@ public class QtNative
                                                 int desktopWidthPixels,
                                                 int desktopHeightPixels,
                                                 double XDpi,
-                                                double YDpi);
+                                                double YDpi,
+                                                double scaledDensity);
     public static native void handleOrientationChanged(int newOrientation);
     // screen methods
 
diff --git a/src/android/jar/src/org/qtproject/qt5/android/QtSurface.java b/src/android/jar/src/org/qtproject/qt5/android/QtSurface.java
index 77126ec1c8..b994a43ac4 100644
--- a/src/android/jar/src/org/qtproject/qt5/android/QtSurface.java
+++ b/src/android/jar/src/org/qtproject/qt5/android/QtSurface.java
@@ -103,7 +103,7 @@ public class QtSurface extends SurfaceView implements SurfaceHolder.Callback
         DisplayMetrics metrics = new DisplayMetrics();
         ((Activity) getContext()).getWindowManager().getDefaultDisplay().getMetrics(metrics);
         QtNative.setApplicationDisplayMetrics(metrics.widthPixels,
-            metrics.heightPixels, getWidth(), getHeight(), metrics.xdpi, metrics.ydpi);
+                                              metrics.heightPixels, getWidth(), getHeight(), metrics.xdpi, metrics.ydpi, metrics.scaledDensity);
 
         if (m_usesGL)
             holder.setFormat(PixelFormat.RGBA_8888);
@@ -136,7 +136,8 @@ public class QtSurface extends SurfaceView implements SurfaceHolder.Callback
                                               width,
                                               height,
                                               metrics.xdpi,
-                                              metrics.ydpi);
+                                              metrics.ydpi,
+                                              metrics.scaledDensity);
 
         if (!m_started)
             return;
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},
diff --git a/src/plugins/platforms/android/src/androidjnimain.h b/src/plugins/platforms/android/src/androidjnimain.h
index 618bd87cdb..f75df55e02 100644
--- a/src/plugins/platforms/android/src/androidjnimain.h
+++ b/src/plugins/platforms/android/src/androidjnimain.h
@@ -81,6 +81,7 @@ namespace QtAndroid
     QWindow *topLevelWindowAt(const QPoint &globalPos);
     int desktopWidthPixels();
     int desktopHeightPixels();
+    double scaledDensity();
     JavaVM *javaVM();
     jclass findClass(const QString &className, JNIEnv *env);
     AAssetManager *assetManager();
diff --git a/src/plugins/platforms/android/src/opengl/qeglfshooks_android.cpp b/src/plugins/platforms/android/src/opengl/qeglfshooks_android.cpp
index cd415843a7..4734d47eb3 100644
--- a/src/plugins/platforms/android/src/opengl/qeglfshooks_android.cpp
+++ b/src/plugins/platforms/android/src/opengl/qeglfshooks_android.cpp
@@ -56,6 +56,7 @@ public:
     EGLNativeDisplayType platformDisplay() const;
     QSize screenSize() const;
     QSizeF physicalScreenSize() const;
+    QDpi logicalDpi() const;
     int screenDepth() const;
     QSurfaceFormat surfaceFormatFor(const QSurfaceFormat &inputFormat) const;
     EGLNativeWindowType createNativeWindow(const QSize &size, const QSurfaceFormat &format);
@@ -86,6 +87,12 @@ QSizeF QEglFSAndroidHooks::physicalScreenSize() const
     return QSizeF(QAndroidPlatformIntegration::m_defaultPhysicalSizeWidth, QAndroidPlatformIntegration::m_defaultPhysicalSizeHeight);
 }
 
+QDpi QEglFSAndroidHooks::logicalDpi() const
+{
+    qreal lDpi = QtAndroid::scaledDensity() * 100;
+    return QDpi(lDpi, lDpi);
+}
+
 
 EGLNativeWindowType QEglFSAndroidHooks::createNativeWindow(const QSize &size, const QSurfaceFormat &format)
 {
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();