1 files changed, 22 insertions, 2 deletions
diff --git a/src/opengl/qwindowsurface_gl.cpp b/src/opengl/qwindowsurface_gl.cpp
index 7efa9bc..e9da452 100644
--- a/src/opengl/qwindowsurface_gl.cpp
+++ b/src/opengl/qwindowsurface_gl.cpp
@@ -354,8 +354,22 @@ void QGLWindowSurface::hijackWindow(QWidget *widget)
     ctx->create(qt_gl_share_widget()->context());
 
 #ifndef QT_NO_EGL
-    if (ctx->d_func()->eglContext->configAttrib(EGL_SWAP_BEHAVIOR) != EGL_BUFFER_PRESERVED)
+    static bool checkedForNOKSwapRegion = false;
+    static bool haveNOKSwapRegion = false;
+
+    if (!checkedForNOKSwapRegion) {
+        haveNOKSwapRegion = QEgl::hasExtension("EGL_NOK_swap_region2");
+        checkedForNOKSwapRegion = true;
+
+        if (haveNOKSwapRegion)
+            qDebug() << "Found EGL_NOK_swap_region2 extension. Using partial updates.";
+    }
+
+    if (ctx->d_func()->eglContext->configAttrib(EGL_SWAP_BEHAVIOR) != EGL_BUFFER_PRESERVED &&
+        ! haveNOKSwapRegion)
         setPartialUpdateSupport(false); // Force full-screen updates
+    else
+        setPartialUpdateSupport(true);
 #endif
 
     widgetPrivate->extraData()->glContext = ctx;
@@ -480,8 +494,14 @@ void QGLWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoint &
                 }
             }
 #endif
+            if (d_ptr->paintedRegion.boundingRect() != geometry()) {
+                // Emits warning if not supported. Should never happen unless
+                // setPartialUpdateSupport(true) has been called.
+                context()->d_func()->swapRegion(&d_ptr->paintedRegion);
+            } else
+                context()->swapBuffers();
+
             d_ptr->paintedRegion = QRegion();
-            context()->swapBuffers();
         } else {
             glFlush();
         }