1 files changed, 17 insertions, 26 deletions

diff --git a/src/opengl/qwindowsurface_gl.cpp b/src/opengl/qwindowsurface_gl.cpp
index eae1c9b..4682d0d 100644
--- a/src/opengl/qwindowsurface_gl.cpp
+++ b/src/opengl/qwindowsurface_gl.cpp
@@ -338,7 +338,7 @@ struct QGLWindowSurfacePrivate
     QGLWindowSurfaceGLPaintDevice glDevice;
     QGLWindowSurface* q_ptr;
 
-    bool partialUpdateSupport;
+    bool swap_region_support;
 };
 
 QGLFormat QGLWindowSurface::surfaceFormat;
@@ -391,7 +391,7 @@ QGLWindowSurface::QGLWindowSurface(QWidget *window)
     d_ptr->q_ptr = this;
     d_ptr->geometry_updated = false;
     d_ptr->did_paint = false;
-    d_ptr->partialUpdateSupport = false;
+    d_ptr->swap_region_support = false;
 }
 
 QGLWindowSurface::~QGLWindowSurface()
@@ -491,22 +491,10 @@ void QGLWindowSurface::hijackWindow(QWidget *widget)
         if (haveNOKSwapRegion)
             qDebug() << "Found EGL_NOK_swap_region2 extension. Using partial updates.";
     }
-    bool swapBehaviourPreserved = (ctx->d_func()->eglContext->configAttrib(EGL_SWAP_BEHAVIOR) != EGL_BUFFER_PRESERVED)
-        || (ctx->d_func()->eglContext->configAttrib(EGL_SURFACE_TYPE)&EGL_SWAP_BEHAVIOR_PRESERVED_BIT);
-    if (ctx->d_func()->eglContext->configAttrib(EGL_SURFACE_TYPE)&EGL_SWAP_BEHAVIOR_PRESERVED_BIT) {
-        EGLint swapBehavior;
-        if (eglQuerySurface(ctx->d_func()->eglContext->display(), ctx->d_func()->eglSurface
-                            , EGL_SWAP_BEHAVIOR, &swapBehavior)) {
-            swapBehaviourPreserved = (swapBehavior == EGL_BUFFER_PRESERVED);
-        }
-    }
 
-    if (!swapBehaviourPreserved && !haveNOKSwapRegion)
-        d_ptr->partialUpdateSupport = false; // Force full-screen updates
-    else
-        d_ptr->partialUpdateSupport = true;
-#else
-    d_ptr->partialUpdateSupport = false;
+    d_ptr->destructive_swap_buffers = !swapBehaviourPreserved;
+
+    d_ptr->swap_region_support = haveNOKSwapRegion;
 #endif
 
     widgetPrivate->extraData()->glContext = ctx;
@@ -622,7 +610,7 @@ void QGLWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoint &
     // mistake to call swapBuffers if nothing was painted unless
     // EGL_BUFFER_PRESERVED is set. This check protects the flush func from
     // being executed if it's for nothing.
-    if (!hasPartialUpdateSupport() && !d_ptr->did_paint)
+    if (!d_ptr->destructive_swap_buffers && !d_ptr->did_paint)
         return;
 
     QWidget *parent = widget->internalWinId() ? widget : widget->nativeParentWidget();
@@ -698,12 +686,12 @@ void QGLWindowSurface::flush(QWidget *widget, const QRegion &rgn, const QPoint &
             }
 #endif
             bool doingPartialUpdate = false;
-            if (QGLWindowSurface::swapBehavior == QGLWindowSurface::AutomaticSwap)
-                doingPartialUpdate = hasPartialUpdateSupport() && br.width() * br.height() < parent->geometry().width() * parent->geometry().height() * 0.2;
-            else if (QGLWindowSurface::swapBehavior == QGLWindowSurface::AlwaysFullSwap)
-                doingPartialUpdate = false;
-            else if (QGLWindowSurface::swapBehavior == QGLWindowSurface::AlwaysPartialSwap)
-                doingPartialUpdate = hasPartialUpdateSupport();
+            if (d_ptr->swap_region_support) {
+                if (QGLWindowSurface::swapBehavior == QGLWindowSurface::AutomaticSwap)
+                    doingPartialUpdate = br.width() * br.height() < parent->geometry().width() * parent->geometry().height() * 0.2;
+                else if (QGLWindowSurface::swapBehavior == QGLWindowSurface::AlwaysPartialSwap)
+                    doingPartialUpdate = true;
+            }
 
             QGLContext *ctx = reinterpret_cast<QGLContext *>(parent->d_func()->extraData()->glContext);
             if (widget != window()) {
@@ -1168,10 +1156,13 @@ QImage *QGLWindowSurface::buffer(const QWidget *widget)
 
 bool QGLWindowSurface::hasPartialUpdateSupport() const
 {
-    return d_ptr->partialUpdateSupport;
+    return !d_ptr->destructive_swap_buffers || d_ptr->swap_region_support;
 }
 
-
+bool QGLWindowSurface::hasPreservedContents() const
+{
+    return !d_ptr->destructive_swap_buffers;
+}
 
 QT_END_NAMESPACE