From 7394aadc24bc5318fdd9498931a882f8b8533365 Mon Sep 17 00:00:00 2001
From: Michael Dominic K <mdk@codethink.co.uk>
Date: Thu, 1 Jul 2010 15:19:51 +0200
Subject: QGLWindowSurface support for partial updates via EGL_NOK_swap_region2
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(if extension available).

Merge-request: 712
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>
---
 src/opengl/qgl.cpp               | 10 ++++++++++
 src/opengl/qgl_egl.cpp           |  8 ++++++++
 src/opengl/qgl_p.h               |  1 +
 src/opengl/qwindowsurface_gl.cpp | 24 ++++++++++++++++++++++--
 4 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index e05db96..72ed0c6 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -2092,6 +2092,16 @@ void QGLContextPrivate::syncGlState()
 }
 #undef ctx
 
+#ifdef QT_NO_EGL
+void QGLContextPrivate::swapRegion(const QRegion *region)
+{
+    static bool firstWarning = true;
+    if (firstWarning) {
+        qWarning() << "::swapRegion called but not supported!";
+        firstWarning = false;
+    }
+}
+#endif
 
 /*!
     \overload
diff --git a/src/opengl/qgl_egl.cpp b/src/opengl/qgl_egl.cpp
index eafa181..3763926 100644
--- a/src/opengl/qgl_egl.cpp
+++ b/src/opengl/qgl_egl.cpp
@@ -274,6 +274,14 @@ EGLSurface QGLContextPrivate::eglSurfaceForDevice() const
     return eglSurface;
 }
 
+void QGLContextPrivate::swapRegion(const QRegion *region)
+{
+    if (!valid || !eglContext)
+        return;
+
+    eglContext->swapBuffersRegion2NOK(eglSurfaceForDevice(), region);
+}
+
 void QGLWidget::setMouseTracking(bool enable)
 {
     QWidget::setMouseTracking(enable);
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 34a6b7c..32feacd 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -334,6 +334,7 @@ public:
 
     void setVertexAttribArrayEnabled(int arrayIndex, bool enabled = true);
     void syncGlState(); // Makes sure the GL context's state is what we think it is
+    void swapRegion(const QRegion *region);
 
 #if defined(Q_WS_WIN)
     void updateFormatVersion();
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();
         }
-- 
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