|author||Tor Arne Vestbø <firstname.lastname@example.org>||2016-09-08 21:51:00 +0200|
|committer||Tor Arne Vestbø <email@example.com>||2016-09-27 20:59:09 +0000|
UIKit: Document the history and implementation of QIOSBackingStore
Change-Id: Icca393afa84bc7dae7f28669a3e73268ffed68b7 Reviewed-by: Richard Moe Gustavsen <firstname.lastname@example.org>
Diffstat (limited to 'src')
1 files changed, 27 insertions, 0 deletions
diff --git a/src/plugins/platforms/ios/qiosbackingstore.mm b/src/plugins/platforms/ios/qiosbackingstore.mm
index 357a3db3c9..076e34c1a5 100644
@@ -66,6 +66,33 @@ void QIOSPaintDevice::ensureActiveTarget()
+ \class QIOSBackingStore
+ \brief The QPlatformBackingStore on iOS.
+ QBackingStore enables the use of QPainter to paint on a QWindow, as opposed
+ to rendering to a QWindow through the use of OpenGL with QOpenGLContext.
+ Historically, the iOS port initially implemented the backing store by using
+ an QOpenGLPaintDevice as its paint device, triggering the use of the OpenGL
+ paint engine for QPainter based drawing. This was due to raster drawing
+ operations being too slow when not being NEON-optimized, and got the port
+ up and running quickly.
+ As of 3e892e4a97, released in Qt 5.7, the backing store now uses a QImage,
+ for its paint device, giving normal raster-based QPainter operations, and
+ enabling features such as antialiased drawing.
+ To account for regressions in performance, the old code path is still
+ available by setting the surface type of the QWindow to OpenGLSurface.
+ This surface type is normally used when rendering though QOpenGLContext,
+ but will in the case of QIOSBackingStore trigger the old OpenGL based
+ This fallback path is not too intrusive, as the QImage based path still
+ uses OpenGL to composite the image at flush() time using composeAndFlush.
, m_context(new QOpenGLContext)