Basic high-dpi "retina" support for Qt 5.

Bring Qt 5 on par with Qt 4, prepare for more comprehensive
support later on.

Introduce device independent pixels (dips), device pixels,
and devicePixelRatio. Add high-dpi support to QPainter,
QGLWidget, the cocoa platform plugin, mac and fusion styles.

Dips are similar to CSS pixels, Apple points and
Android density-independent pixels. Device pixels
are pixels in the backing store/physical pixels on screen.
devicePixelRatio is the ratio between them, which is
1.0 on standard displays and 2.0 on "retina" displays.

New API:
QImage::devicePixelRatio() and setDevicePixelRatio()
QPixmap::devicePixelRatio() and setDevicePixelRatio()
QWindow::devicePixelRatio()
QScreen::devicePixelRatio()
QGuiApplicaiton::devicePixelRatio()

Change-Id: If98c3ca9bfdf0e1bdbcf7574cd5b912c9ff63856
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.mm b/src/plugins/platforms/cocoa/qcocoaintegration.mm
index 3767fa014d..393c471c25 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.mm
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.mm
@@ -115,6 +115,18 @@ void QCocoaScreen::updateGeometry()
     QWindowSystemInterface::handleScreenAvailableGeometryChange(screen(), availableGeometry());
 }
 
+qreal QCocoaScreen::devicePixelRatio() const
+{
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
+    if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_7) {
+        return qreal([m_screen backingScaleFactor]);
+    } else
+#endif
+    {
+        return 1.0;
+    }
+}
+
 extern CGContextRef qt_mac_cg_context(const QPaintDevice *pdev);
 
 QPixmap QCocoaScreen::grabWindow(WId window, int x, int y, int width, int height) const