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, 15 insertions, 0 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index 77073d9bc6..c3b2139998 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -39,6 +39,7 @@
 **
 ****************************************************************************/
 #include "qcocoawindow.h"
+#include "qcocoaintegration.h"
 #include "qnswindowdelegate.h"
 #include "qcocoaautoreleasepool.h"
 #include "qcocoaeventdispatcher.h"
@@ -820,6 +821,20 @@ QCocoaMenuBar *QCocoaWindow::menubar() const
     return m_menubar;
 }
 
+qreal QCocoaWindow::devicePixelRatio() const
+{
+    if (!m_nsWindow)
+        return 1.0;
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
+    if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_7) {
+        return qreal([m_nsWindow backingScaleFactor]);
+    } else
+#endif
+    {
+        return 1.0;
+    }
+}
+
 QMargins QCocoaWindow::frameMargins() const
 {
     NSRect frameW = [m_nsWindow frame];