5 files changed, 114 insertions, 14 deletions
diff --git a/src/gui/kernel/qplatformscreen_qpa.cpp b/src/gui/kernel/qplatformscreen_qpa.cpp
index 1a8e6d8f7c..86dc0bd588 100644
--- a/src/gui/kernel/qplatformscreen_qpa.cpp
+++ b/src/gui/kernel/qplatformscreen_qpa.cpp
@@ -127,20 +127,41 @@ QScreen *QPlatformScreen::screen() const
 
 /*!
     Reimplement this function in subclass to return the physical size of the
-    screen. This function is used by QFont to convert point sizes to pixel
-    sizes.
+    screen. The physical size represents the actual physical dimensions of
+    the display.
 
     The default implementation takes the pixel size of the screen, considers a
     resolution of 100 dots per inch, and returns the calculated physical size.
     A device with a screen that has different resolutions will need to be
     supported by a suitable reimplementation of this function.
+
+    \sa logcalDpi
 */
-QSize QPlatformScreen::physicalSize() const
+QSizeF QPlatformScreen::physicalSize() const
 {
     static const int dpi = 100;
-    int width = geometry().width() / dpi * qreal(25.4) ;
-    int height = geometry().height() / dpi * qreal(25.4) ;
-    return QSize(width,height);
+    return QSizeF(geometry().size()) / dpi * qreal(25.4);
+}
+
+/*!
+    Reimplement this function in subclass to return the logical horizontal
+    and vertical dots per inch metrics of the screen.
+
+    The logical dots per inch metrics are used by QFont to convert point sizes
+    to pixel sizes.
+
+    The default implementation uses the screen pixel size and physical size to
+    compute the metrics.
+
+    \sa physicalSize
+*/
+QDpi QPlatformScreen::logicalDpi() const
+{
+    QSizeF ps = physicalSize();
+    QSize s = geometry().size();
+
+    return QDpi(25.4 * s.width() / ps.width(),
+                25.4 * s.height() / ps.height());
 }
 
 QPlatformScreen * QPlatformScreen::platformScreenForWindow(const QWindow *window)
diff --git a/src/gui/kernel/qplatformscreen_qpa.h b/src/gui/kernel/qplatformscreen_qpa.h
index 7c20fba0ba..6917d5eca5 100644
--- a/src/gui/kernel/qplatformscreen_qpa.h
+++ b/src/gui/kernel/qplatformscreen_qpa.h
@@ -67,6 +67,8 @@ class QPlatformWindow;
 class QScreen;
 class QSurfaceFormat;
 
+typedef QPair<qreal, qreal> QDpi;
+
 class Q_GUI_EXPORT QPlatformScreenPageFlipper : public QObject
 {
     Q_OBJECT
@@ -93,7 +95,9 @@ public:
 
     virtual int depth() const = 0;
     virtual QImage::Format format() const = 0;
-    virtual QSize physicalSize() const;
+
+    virtual QSizeF physicalSize() const;
+    virtual QDpi logicalDpi() const;
 
     virtual QWindow *topLevelAt(const QPoint &point) const;
     virtual QList<QPlatformScreen *> virtualSiblings() const;
diff --git a/src/gui/kernel/qscreen.cpp b/src/gui/kernel/qscreen.cpp
index 96ed2bd410..c2049af1e5 100644
--- a/src/gui/kernel/qscreen.cpp
+++ b/src/gui/kernel/qscreen.cpp
@@ -102,6 +102,75 @@ QSize QScreen::size() const
 }
 
 /*!
+  Gets the number of physical dots or pixels per inch in the horizontal direction.
+
+  This value represents the actual horizontal pixel density on the screen's display.
+  Depending on what information the underlying system provides the value might not be
+  entirely accurate.
+
+  \sa physicalDotsPerInchY()
+*/
+qreal QScreen::physicalDotsPerInchX() const
+{
+    return size().width() / physicalSize().width() * 25.4;
+}
+
+/*!
+  Gets the number of physical dots or pixels per inch in the vertical direction.
+
+  This value represents the actual vertical pixel density on the screen's display.
+  Depending on what information the underlying system provides the value might not be
+  entirely accurate.
+
+  \sa physicalDotsPerInchX()
+*/
+qreal QScreen::physicalDotsPerInchY() const
+{
+    return size().height() / physicalSize().height() * 25.4;
+}
+
+/*!
+  Gets the number of logical dots or pixels per inch in the horizontal direction.
+
+  This value is used to convert font point sizes to pixel sizes.
+
+  \sa logicalDotsPerInchY()
+*/
+qreal QScreen::logicalDotsPerInchX() const
+{
+    Q_D(const QScreen);
+    return d->platformScreen->logicalDpi().first;
+}
+
+/*!
+  Gets the number of logical dots or pixels per inch in the vertical direction.
+
+  This value is used to convert font point sizes to pixel sizes.
+
+  \sa logicalDotsPerInchX()
+*/
+qreal QScreen::logicalDotsPerInchY() const
+{
+    Q_D(const QScreen);
+    return d->platformScreen->logicalDpi().second;
+}
+
+/*!
+  Get the screen's physical size (in millimeters).
+
+  The physical size represents the actual physical dimensions of the
+  screen's display.
+
+  Depending on what information the underlying system provides the value
+  might not be entirely accurate.
+*/
+QSizeF QScreen::physicalSize() const
+{
+    Q_D(const QScreen);
+    return d->platformScreen->physicalSize();
+}
+
+/*!
   Get the screen's available size.
 
   The available size is the size excluding window manager reserved areas
diff --git a/src/gui/kernel/qscreen.h b/src/gui/kernel/qscreen.h
index ea068cd834..72681eb6da 100644
--- a/src/gui/kernel/qscreen.h
+++ b/src/gui/kernel/qscreen.h
@@ -44,6 +44,9 @@
 
 #include <QtCore/QList>
 #include <QtCore/QObject>
+#include <QtCore/QRect>
+#include <QtCore/QSize>
+#include <QtCore/QSizeF>
 
 QT_BEGIN_HEADER
 
@@ -54,7 +57,6 @@ QT_MODULE(Gui)
 class QPlatformScreen;
 class QScreenPrivate;
 class QWindow;
-class QSize;
 class QRect;
 
 class Q_GUI_EXPORT QScreen : public QObject
@@ -72,6 +74,14 @@ public:
     QSize size() const;
     QRect geometry() const;
 
+    QSizeF physicalSize() const;
+
+    qreal physicalDotsPerInchX() const;
+    qreal physicalDotsPerInchY() const;
+
+    qreal logicalDotsPerInchX() const;
+    qreal logicalDotsPerInchY() const;
+
     QSize availableSize() const;
     QRect availableGeometry() const;
 
diff --git a/src/gui/text/qfont.cpp b/src/gui/text/qfont.cpp
index e8308dba06..3d2dfb9c76 100644
--- a/src/gui/text/qfont.cpp
+++ b/src/gui/text/qfont.cpp
@@ -170,9 +170,7 @@ Q_GUI_EXPORT int qt_defaultDpiX()
 #elif defined(Q_WS_QPA)
     QScreen *screen = QGuiApplication::primaryScreen();
     if (screen) {
-        const QSize screenSize = screen->geometry().size();
-        const QSize physicalSize = screen->handle()->physicalSize();
-        dpi = qRound(screenSize.width() / (physicalSize.width() / qreal(25.4)));
+        dpi = qRound(screen->logicalDotsPerInchX());
     } else {
         //PI has not been initialised, or it is being initialised. Give a default dpi
         dpi = 100;
@@ -200,9 +198,7 @@ Q_GUI_EXPORT int qt_defaultDpiY()
 #elif defined(Q_WS_QPA)
     QScreen *screen = QGuiApplication::primaryScreen();
     if (screen) {
-        const QSize screenSize = screen->geometry().size();
-        const QSize physicalSize = screen->handle()->physicalSize();
-        dpi = qRound(screenSize.height() / (physicalSize.height() / qreal(25.4)));
+        dpi = qRound(screen->logicalDotsPerInchY());
     } else {
         //PI has not been initialised, or it is being initialised. Give a default dpi
         dpi = 100;