iOS: Allow QBackingStore::flush() without beginPaint()

The QBackingStore API doesn't require clients to precede flush() with a
beginPaint() call, but our backingstore is backed by a GL context, so
it's up to us to ensure it's current before swapping.

Change-Id: Ia6119bf0e835448b1fd383d933df6f88fa4f298a
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/src/plugins/platforms/ios/qiosbackingstore.mm b/src/plugins/platforms/ios/qiosbackingstore.mm
index 2dadc5672b..80b603bb8e 100644
--- a/src/plugins/platforms/ios/qiosbackingstore.mm
+++ b/src/plugins/platforms/ios/qiosbackingstore.mm
@@ -56,6 +56,9 @@ QIOSBackingStore::QIOSBackingStore(QWindow *window)
     fmt.setDepthBufferSize(16);
     fmt.setStencilBufferSize(8);
 
+    // Needed to prevent QOpenGLContext::makeCurrent() from failing
+    window->setSurfaceType(QSurface::OpenGLSurface);
+
     m_context->setFormat(fmt);
     m_context->setScreen(window->screen());
     m_context->create();
@@ -69,9 +72,6 @@ QIOSBackingStore::~QIOSBackingStore()
 
 void QIOSBackingStore::beginPaint(const QRegion &)
 {
-    // Needed to prevent QOpenGLContext::makeCurrent() from failing
-    window()->setSurfaceType(QSurface::OpenGLSurface);
-
     m_context->makeCurrent(window());
 
     QIOSWindow *iosWindow = static_cast<QIOSWindow *>(window()->handle());
@@ -102,6 +102,8 @@ void QIOSBackingStore::flush(QWindow *window, const QRegion &region, const QPoin
         // the child window overlaps a sibling window that's draws using a separate QOpenGLContext.
         return;
     }
+
+    m_context->makeCurrent(window);
     m_context->swapBuffers(window);
 }