doc: Brush up QPaintEngine documentation for Qt 5

The paint engine story has changed drastically in Qt 5,
and we no longer need the reference to Qt 3.

Change-Id: I66090582e5c66d2a3cd9de355c34b33a94b67dfe
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

diff --git a/src/gui/painting/qpaintengine.cpp b/src/gui/painting/qpaintengine.cpp
index 91c4e35..09b1f0a 100644 (file)
--- a/src/gui/painting/qpaintengine.cpp
+++ b/src/gui/painting/qpaintengine.cpp
@@ -152,14 +152,16 @@ QFont QTextItem::font() const
   \brief The QPaintEngine class provides an abstract definition of how
   QPainter draws to a given device on a given platform.
 
-  Qt 4.0 provides several premade implementations of QPaintEngine for the
-  different painter backends we support. We provide one paint engine for each
-  window system and painting framework we support. This includes X11 on
-  Unix/Linux and CoreGraphics on Mac OS X. In addition we provide QPaintEngine
-  implementations for OpenGL (accessible through QOpenGLWidget) and PostScript
-  (accessible through QPSPrinter on X11). Additionally there is a raster-based
-  paint engine that is a fallback for when an engine does not support a certain
-  capability.
+  Qt provides several premade implementations of QPaintEngine for the
+  different painter backends we support. The primary paint engine
+  provided is the raster paint engine, which contains a software
+  rasterizer which supports the full feature set on all supported platforms.
+  This is the default for painting on QWidget-based classes in e.g. on Windows,
+  X11 and Mac OS X, it is the backend for painting on QImage and it is
+  used as a fallback for paint engines that do not support a certain
+  capability. In addition we provide QPaintEngine implementations for
+  OpenGL (accessible through QGLWidget) and printing (which allows using
+  QPainter to draw on a QPrinter object).
 
   If one wants to use QPainter to draw to a different backend,
   one must subclass QPaintEngine and reimplement all its virtual
@@ -169,11 +171,6 @@ QFont QTextItem::font() const
 
   QPaintEngine is created and owned by the QPaintDevice that created it.
 
-  The big advantage of the QPaintEngine approach opposed to
-  Qt 3's QPainter/QPaintDevice::cmd() approach is that it is now
-  possible to adapt to multiple technologies on each platform and take
-  advantage of each to the fullest.
-
   \sa QPainter, QPaintDevice::paintEngine(), {Paint System}
 */