Introduced QOpenGLContext::aboutToBeDestroyed() signal.

This signal can be used to clean up OpenGL resources in a safe way
before the context is destroyed.

Task-number: QTBUG-20083
Change-Id: I45a4be01b06af4ee7196fa502116f099d50afeab
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>

2 files changed, 16 insertions, 0 deletions

diff --git a/src/gui/kernel/qopenglcontext.cpp b/src/gui/kernel/qopenglcontext.cpp
index 6a9cb43028..29a9e92e5c 100644
--- a/src/gui/kernel/qopenglcontext.cpp
+++ b/src/gui/kernel/qopenglcontext.cpp
@@ -174,6 +174,8 @@ bool QOpenGLContext::create()
 void QOpenGLContext::destroy()
 {
     Q_D(QOpenGLContext);
+    if (d->platformGLContext)
+        emit aboutToBeDestroyed();
     if (QOpenGLContext::currentContext() == this)
         doneCurrent();
     if (d->shareGroup)
@@ -186,6 +188,17 @@ void QOpenGLContext::destroy()
 }
 
 /*!
+    \fn void QOpenGLContext::aboutToBeDestroyed()
+
+    This signal is emitted before the underlying native OpenGL context is
+    destroyed, such that users may clean up OpenGL resources that might otherwise
+    be left dangling in the case of shared OpenGL contexts.
+
+    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.
+*/
+
+/*!
   If this is the current context for the thread, doneCurrent is called
 */
 QOpenGLContext::~QOpenGLContext()
diff --git a/src/gui/kernel/qopenglcontext.h b/src/gui/kernel/qopenglcontext.h
index b5a19a0ebc..0d02cfe613 100644
--- a/src/gui/kernel/qopenglcontext.h
+++ b/src/gui/kernel/qopenglcontext.h
@@ -118,6 +118,9 @@ public:
 
     QOpenGLFunctions *functions() const;
 
+Q_SIGNALS:
+    void aboutToBeDestroyed();
+
 private:
     friend class QGLContext;
     friend class QOpenGLContextResourceBase;