path: root/src/platformsupport
diff options
authorLaszlo Agocs <>2014-09-01 10:43:42 +0200
committerLaszlo Agocs <>2014-09-01 14:10:12 +0200
commitda2b3c4479e1d23ea6ead555cadc96a56967887a (patch)
tree20ebe47749dcf233f70f3db00d22125c41116e5c /src/platformsupport
parentd06fb5609c02d639e44e932988f428c13aab71c3 (diff)
Prevent current context from becoming inconsistent upon create()
Platform plugins have a tendency to make the newly created native context current with a temporary surface. This is usually needed to query some information related to the new context. Afterwards most of them just reset to having nothing current. This has two issues: It unexpectedly changes the current context/surface. A call into QOpenGLContext::create() does not imply that the current context will get changed. This is the minor issue and we could probably live with it (at least if it had been documented). However, the real issue is that QOpenGLContext::currentContext() will become inconsistent: it will still report whatever was current before the create() even though on the EGL/WGL/GLX level that's not the case anymore. To prevent all this confusion the platform plugins can easily be changed to restore whatever context/surface was current before they altered it. Change-Id: I6a5b4597c86571327524ddb13e0d02538593cc7b Reviewed-by: Friedemann Kleint <> Reviewed-by: Gunnar Sletta <>
Diffstat (limited to 'src/platformsupport')
1 files changed, 10 insertions, 1 deletions
diff --git a/src/platformsupport/eglconvenience/qeglplatformcontext.cpp b/src/platformsupport/eglconvenience/qeglplatformcontext.cpp
index 148c5d9b2f..dce8bd888c 100644
--- a/src/platformsupport/eglconvenience/qeglplatformcontext.cpp
+++ b/src/platformsupport/eglconvenience/qeglplatformcontext.cpp
@@ -249,6 +249,15 @@ void QEGLPlatformContext::adopt(const QVariant &nativeHandle, QPlatformOpenGLCon
void QEGLPlatformContext::updateFormatFromGL()
#ifndef QT_NO_OPENGL
+ // Have to save & restore to prevent QOpenGLContext::currentContext() from becoming
+ // inconsistent after QOpenGLContext::create().
+ EGLDisplay prevDisplay = eglGetCurrentDisplay();
+ if (prevDisplay == EGL_NO_DISPLAY) // when no context is current
+ prevDisplay = m_eglDisplay;
+ EGLContext prevContext = eglGetCurrentContext();
+ EGLSurface prevSurfaceDraw = eglGetCurrentSurface(EGL_DRAW);
+ EGLSurface prevSurfaceRead = eglGetCurrentSurface(EGL_READ);
// Make the context current to ensure the GL version query works. This needs a surface too.
const EGLint pbufferAttributes[] = {
@@ -300,7 +309,7 @@ void QEGLPlatformContext::updateFormatFromGL()
- eglMakeCurrent(m_eglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
+ eglMakeCurrent(prevDisplay, prevSurfaceDraw, prevSurfaceRead, prevContext);
eglDestroySurface(m_eglDisplay, pbuffer);
#endif // QT_NO_OPENGL