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, 5 insertions, 2 deletions

diff --git a/src/gui/image/qimage_p.h b/src/gui/image/qimage_p.h
index 74a79a8425..2bb989c03b 100644
--- a/src/gui/image/qimage_p.h
+++ b/src/gui/image/qimage_p.h
@@ -74,6 +74,7 @@ struct Q_GUI_EXPORT QImageData {        // internal image data
     int height;
     int depth;
     int nbytes;               // number of bytes data
+    qreal devicePixelRatio;
     QVector<QRgb> colortable;
     uchar *data;
     QImage::Format format;
@@ -81,8 +82,10 @@ struct Q_GUI_EXPORT QImageData {        // internal image data
     int ser_no;               // serial number
     int detach_no;
 
-    qreal  dpmx;                // dots per meter X (or 0)
-    qreal  dpmy;                // dots per meter Y (or 0)
+    qreal  ldpmx;               // logical dots per meter X (or 0)
+    qreal  ldpmy;               // logical dots per meter Y (or 0)
+    qreal  dpmx;                // device dots per meter X (or 0)
+    qreal  dpmy;                // device dots per meter Y (or 0)
     QPoint  offset;           // offset in pixels
 
     uint own_data : 1;