From aaf16b2f4367cf3ab1c4c025093806242ecd03eb Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Tor=20Arne=20Vestb=C3=B8?= Date: Thu, 8 Sep 2016 21:51:00 +0200 Subject: UIKit: Document the history and implementation of QIOSBackingStore Change-Id: Icca393afa84bc7dae7f28669a3e73268ffed68b7 Reviewed-by: Richard Moe Gustavsen --- src/plugins/platforms/ios/qiosbackingstore.mm | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) (limited to 'src/plugins/platforms/ios') 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) -- cgit v1.2.3