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, 6 insertions, 4 deletions

diff --git a/src/widgets/itemviews/qitemdelegate.cpp b/src/widgets/itemviews/qitemdelegate.cpp
index e7ca2d0c6c..7631403933 100644
--- a/src/widgets/itemviews/qitemdelegate.cpp
+++ b/src/widgets/itemviews/qitemdelegate.cpp
@@ -1060,10 +1060,12 @@ QRect QItemDelegate::rect(const QStyleOptionViewItem &option,
         switch (value.type()) {
         case QVariant::Invalid:
             break;
-        case QVariant::Pixmap:
-            return QRect(QPoint(0, 0), qvariant_cast<QPixmap>(value).size());
-        case QVariant::Image:
-            return QRect(QPoint(0, 0), qvariant_cast<QImage>(value).size());
+        case QVariant::Pixmap: {
+            const QPixmap &pixmap = qvariant_cast<QPixmap>(value);
+            return QRect(QPoint(0, 0), pixmap.size() / pixmap.devicePixelRatio() ); }
+        case QVariant::Image: {
+            const QImage &image = qvariant_cast<QImage>(value);
+            return QRect(QPoint(0, 0), image.size() /  image.devicePixelRatio() ); }
         case QVariant::Icon: {
             QIcon::Mode mode = d->iconMode(option.state);
             QIcon::State state = d->iconState(option.state);