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, 22 insertions, 4 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoabackingstore.mm b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
index 7bd7e4ce38..ec3168ce99 100644
--- a/src/plugins/platforms/cocoa/qcocoabackingstore.mm
+++ b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
@@ -59,10 +59,22 @@ QCocoaBackingStore::~QCocoaBackingStore()
 
 QPaintDevice *QCocoaBackingStore::paintDevice()
 {
-    if (m_qImage.size() != m_requestedSize) {
+    if (m_qImage.size() / m_qImage.devicePixelRatio() != m_requestedSize) {
         CGImageRelease(m_cgImage);
         m_cgImage = 0;
-        m_qImage = QImage(m_requestedSize, QImage::Format_ARGB32_Premultiplied);
+
+        int scaleFactor = 1;
+#if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
+        if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_7) {
+            QCocoaWindow *cocoaWindow = static_cast<QCocoaWindow *>(window()->handle());
+            if (cocoaWindow && cocoaWindow->m_contentView) {
+                scaleFactor = int([[cocoaWindow->m_contentView window] backingScaleFactor]);
+            }
+        }
+#endif
+
+        m_qImage = QImage(m_requestedSize * scaleFactor, QImage::Format_ARGB32_Premultiplied);
+        m_qImage.setDevicePixelRatio(scaleFactor);
     }
     return &m_qImage;
 }
@@ -90,10 +102,11 @@ void QCocoaBackingStore::resize(const QSize &size, const QRegion &)
 bool QCocoaBackingStore::scroll(const QRegion &area, int dx, int dy)
 {
     extern void qt_scrollRectInImage(QImage &img, const QRect &rect, const QPoint &offset);
-    QPoint qpoint(dx, dy);
+    const qreal devicePixelRatio = m_qImage.devicePixelRatio();
+    QPoint qpoint(dx * devicePixelRatio, dy * devicePixelRatio);
     const QVector<QRect> qrects = area.rects();
     for (int i = 0; i < qrects.count(); ++i) {
-        const QRect &qrect = qrects.at(i);
+        const QRect &qrect = QRect(qrects.at(i).topLeft() * devicePixelRatio, qrects.at(i).size() * devicePixelRatio);
         qt_scrollRectInImage(m_qImage, qrect, qpoint);
     }
     return true;
@@ -110,4 +123,9 @@ CGImageRef QCocoaBackingStore::getBackingStoreCGImage()
     return m_cgImage;
 }
 
+qreal QCocoaBackingStore::getBackingStoreDevicePixelRatio()
+{
+    return m_qImage.devicePixelRatio();
+}
+
 QT_END_NAMESPACE