1 files changed, 49 insertions, 14 deletions

diff --git a/src/gui/kernel/qopenglcontext.cpp b/src/gui/kernel/qopenglcontext.cpp
index 99c13257a3..02781f4aa0 100644
--- a/src/gui/kernel/qopenglcontext.cpp
+++ b/src/gui/kernel/qopenglcontext.cpp
@@ -42,7 +42,7 @@ static QOpenGLContext *global_share_context = nullptr;
 
 #ifndef QT_NO_DEBUG
 QHash<QOpenGLContext *, bool> QOpenGLContextPrivate::makeCurrentTracker;
-QMutex QOpenGLContextPrivate::makeCurrentTrackerMutex;
+Q_CONSTINIT QMutex QOpenGLContextPrivate::makeCurrentTrackerMutex;
 #endif
 
 /*!
@@ -69,6 +69,7 @@ QOpenGLContext *qt_gl_global_share_context()
 
 /*!
     \class QOpenGLContext
+    \ingroup painting-3D
     \inmodule QtGui
     \since 5.0
     \brief The QOpenGLContext class represents a native OpenGL context, enabling
@@ -137,6 +138,22 @@ QOpenGLContext *qt_gl_global_share_context()
     application is portable between different platforms. However, if you use
     QOpenGLFunctions::glBindFramebuffer(), this is done automatically for you.
 
+    \warning WebAssembly
+
+    We recommend that only one QOpenGLContext is made current with a QSurface,
+    for the entire lifetime of the QSurface. Should more than once context be used,
+    it is important to understand that multiple QOpenGLContext instances may be
+    backed by the same native context underneath with the WebAssembly platform.
+    Therefore, calling makeCurrent() with the same QSurface on two QOpenGLContext
+    objects may not switch to a different native context in the second call. As
+    a result, any OpenGL state changes done after the second makeCurrent() may
+    alter the state of the first QOpenGLContext as well, as they are all backed
+    by the same native context.
+
+    \note This means that when targeting WebAssembly with existing OpenGL-based
+    Qt code, some porting may be required to cater to these limitations.
+
+
     \sa QOpenGLFunctions, QOpenGLBuffer, QOpenGLShaderProgram, QOpenGLFramebufferObject
 */
 
@@ -362,10 +379,6 @@ bool QOpenGLContext::create()
 
 QOpenGLContextPrivate::~QOpenGLContextPrivate()
 {
-    //do not delete the QOpenGLContext handle here as it is deleted in
-    //QWidgetPrivate::deleteTLSysExtra()
-
-    delete versionFunctions;
 }
 
 void QOpenGLContextPrivate::adopt(QPlatformOpenGLContext *context)
@@ -403,30 +416,47 @@ void QOpenGLContextPrivate::adopt(QPlatformOpenGLContext *context)
 void QOpenGLContext::destroy()
 {
     Q_D(QOpenGLContext);
+
+    // Notify that the native context and the QPlatformOpenGLContext are going
+    // to go away.
     if (d->platformGLContext)
         emit aboutToBeDestroyed();
-    if (QOpenGLContext::currentContext() == this)
-        doneCurrent();
-    if (d->shareGroup)
-        d->shareGroup->d_func()->removeContext(this);
-    d->shareGroup = nullptr;
-    delete d->platformGLContext;
-    d->platformGLContext = nullptr;
-    delete d->functions;
-    d->functions = nullptr;
 
+    // Invoke callbacks for helpers and invalidate.
     if (d->textureFunctionsDestroyCallback) {
         d->textureFunctionsDestroyCallback();
         d->textureFunctionsDestroyCallback = nullptr;
     }
     d->textureFunctions = nullptr;
 
+    delete d->versionFunctions;
+    d->versionFunctions = nullptr;
+
     if (d->vaoHelperDestroyCallback) {
         Q_ASSERT(d->vaoHelper);
         d->vaoHelperDestroyCallback(d->vaoHelper);
         d->vaoHelperDestroyCallback = nullptr;
     }
     d->vaoHelper = nullptr;
+
+    // Tear down function wrappers.
+    delete d->versionFunctions;
+    d->versionFunctions = nullptr;
+
+    delete d->functions;
+    d->functions = nullptr;
+
+    // Clean up and destroy the native context machinery.
+    if (QOpenGLContext::currentContext() == this)
+        doneCurrent();
+
+    if (d->shareGroup)
+        d->shareGroup->d_func()->removeContext(this);
+
+    d->shareGroup = nullptr;
+
+    delete d->platformGLContext;
+    d->platformGLContext = nullptr;
 }
 
 /*!
@@ -438,6 +468,11 @@ void QOpenGLContext::destroy()
 
     If you wish to make the context current in order to do clean-up, make sure
     to only connect to the signal using a direct connection.
+
+    \note In Qt for Python, this signal will not be received when emitted
+    from the destructor of QOpenGLWidget or QOpenGLWindow due to the Python
+    instance already being destroyed. We recommend doing cleanups
+    in QWidget::hideEvent() instead.
 */
 
 /*!