Set EGL_SWAP_BEHAVIOR to EGL_BUFFER_PRESERVED for regular QWidgets

QGLWidgets are assumed to be buffer destroyed, however regular
QWidgets assume they can to partial updates and thus need the
preserved swap behaviour.

Reviewed-By: Trond
Task-number: QTBUG-9554

2 files changed, 7 insertions, 0 deletions

diff --git a/src/gui/egl/qeglproperties.cpp b/src/gui/egl/qeglproperties.cpp
index 5543547..3638de5 100644
--- a/src/gui/egl/qeglproperties.cpp
+++ b/src/gui/egl/qeglproperties.cpp
@@ -241,6 +241,9 @@ void QEglProperties::setRenderableType(QEgl::API api)
 // reductions in complexity are possible.
 bool QEglProperties::reduceConfiguration()
 {
+    if (value(EGL_SWAP_BEHAVIOR) != EGL_DONT_CARE)
+        removeValue(EGL_SWAP_BEHAVIOR);
+
 #ifdef EGL_VG_ALPHA_FORMAT_PRE_BIT
     // For OpenVG, we sometimes try to create a surface using a pre-multiplied format. If we can't
     // find a config which supports pre-multiplied formats, remove the flag on the surface type:
diff --git a/src/opengl/qgl_x11egl.cpp b/src/opengl/qgl_x11egl.cpp
index 6f210ce..d67a3ea 100644
--- a/src/opengl/qgl_x11egl.cpp
+++ b/src/opengl/qgl_x11egl.cpp
@@ -199,6 +199,10 @@ bool QGLContext::chooseContext(const QGLContext* shareContext)
         configProps.setRenderableType(QEgl::OpenGL);
         qt_eglproperties_set_glformat(configProps, d->glFormat);
 
+        // Set buffer preserved for regular QWidgets, QGLWidgets are ok with either preserved or destroyed:
+        if ((devType == QInternal::Widget) && qobject_cast<QGLWidget*>(static_cast<QWidget*>(device())) == 0)
+            configProps.setValue(EGL_SWAP_BEHAVIOR, EGL_BUFFER_PRESERVED);
+
         if (!d->eglContext->chooseConfig(configProps, QEgl::BestPixelFormat)) {
             delete d->eglContext;
             d->eglContext = 0;