diff options
author | Tor Arne Vestbø <tor.arne.vestbo@qt.io> | 2016-09-08 21:51:00 +0200 |
---|---|---|
committer | Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com> | 2016-09-27 20:59:09 +0000 |
commit | aaf16b2f4367cf3ab1c4c025093806242ecd03eb (patch) | |
tree | f21c810174ffaf6d248556a343758dc4968becc9 /src/plugins/platforms/ios | |
parent | cd78457c6d33bdd7c01fbcd78e50bc99e9c9acce (diff) |
UIKit: Document the history and implementation of QIOSBackingStore
Change-Id: Icca393afa84bc7dae7f28669a3e73268ffed68b7
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
Diffstat (limited to 'src/plugins/platforms/ios')
-rw-r--r-- | src/plugins/platforms/ios/qiosbackingstore.mm | 27 |
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 --- a/src/plugins/platforms/ios/qiosbackingstore.mm +++ b/src/plugins/platforms/ios/qiosbackingstore.mm @@ -66,6 +66,33 @@ void QIOSPaintDevice::ensureActiveTarget() m_backingStore->makeCurrent(); } +/*! + \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 + painter. + + This fallback path is not too intrusive, as the QImage based path still + uses OpenGL to composite the image at flush() time using composeAndFlush. +*/ QIOSBackingStore::QIOSBackingStore(QWindow *window) : QRasterBackingStore(window) , m_context(new QOpenGLContext) |