Fix to QGLWidget rendering with VG graphics system

QEGLContext don't expect EGL based API to change
on runtime (e.g. VG->GL). QEGLContext caches current API
context pointer and uses this cached value to determine whether
to make eglMakeCurrent call or not. VG graphics system and
QGLWidget creates own separate QEGLContext objects, but both
of those objects consider themself to be current context, so
no eglMakeCurrent call occurs even though the API has changed.
This patch adds ifdef'd current context check for Symbian
which enables eglMakeCurrent call if EGL API has changed.
(Symbian is the only supported platform currently where this scenario happens).

Task-number: QT-5012
Reviewed-by: Samuel Rødal

2 files changed, 21 insertions, 1 deletions

diff --git a/src/gui/egl/qegl.cpp b/src/gui/egl/qegl.cpp
index d9c5ea2..4db4a6a 100644
--- a/src/gui/egl/qegl.cpp
+++ b/src/gui/egl/qegl.cpp
@@ -94,6 +94,7 @@ QEglContext::QEglContext()
     , current(false)
     , ownsContext(true)
     , sharing(false)
+    , apiChanged(false)
 {
     QEglContextTracker::ref();
 }
@@ -435,9 +436,20 @@ bool QEglContext::makeCurrent(EGLSurface surface)
         return false;
     }
 
+#ifdef Q_OS_SYMBIAN
+    apiChanged = false;
+    if (currentContext(apiType)
+            && currentContext(apiType)->ctx != eglGetCurrentContext()) {
+        // some other EGL based API active. Complete its rendering
+        eglWaitClient();
+        apiChanged = true;
+    }
+#endif
+
     // If lazyDoneCurrent() was called on the surface, then we may be able
     // to assume that it is still current within the thread.
-    if (surface == currentSurface && currentContext(apiType) == this) {
+    if (surface == currentSurface && currentContext(apiType) == this
+            && !apiChanged) {
         current = true;
         return true;
     }
@@ -512,6 +524,13 @@ bool QEglContext::swapBuffers(EGLSurface surface)
     bool ok = eglSwapBuffers(QEgl::display(), surface);
     if (!ok)
         qWarning() << "QEglContext::swapBuffers():" << QEgl::errorString();
+
+#ifdef Q_OS_SYMBIAN
+    if (apiChanged) {
+        eglWaitClient();
+        apiChanged = false;
+    }
+#endif
     return ok;
 }
 
diff --git a/src/gui/egl/qeglcontext_p.h b/src/gui/egl/qeglcontext_p.h
index 6cd76b3..0cdaae7 100644
--- a/src/gui/egl/qeglcontext_p.h
+++ b/src/gui/egl/qeglcontext_p.h
@@ -104,6 +104,7 @@ private:
     bool current;
     bool ownsContext;
     bool sharing;
+    bool apiChanged;
 
     static QEglContext *currentContext(QEgl::API api);
     static void setCurrentContext(QEgl::API api, QEglContext *context);