Enabled compilation of both GL and GL2 paint engine.

Compile both GL and GL2 paint engine on desktop, and choose between them
at run-time based on GL version flags.

Reviewed-by: Tom

13 files changed, 109 insertions, 124 deletions

diff --git a/src/opengl/gl2paintengineex/qglgradientcache.cpp b/src/opengl/gl2paintengineex/qglgradientcache.cpp
index b4591b2..59d4bf8 100644
--- a/src/opengl/gl2paintengineex/qglgradientcache.cpp
+++ b/src/opengl/gl2paintengineex/qglgradientcache.cpp
@@ -44,7 +44,7 @@
 
 #include "qglgradientcache_p.h"
 
-void QGLGradientCache::cleanCache() {
+void QGL2GradientCache::cleanCache() {
     QGLGradientColorTableHash::const_iterator it = cache.constBegin();
     for (; it != cache.constEnd(); ++it) {
         const CacheInfo &cache_info = it.value();
@@ -53,7 +53,7 @@ void QGLGradientCache::cleanCache() {
     cache.clear();
 }
 
-GLuint QGLGradientCache::getBuffer(const QGradient &gradient, qreal opacity, const QGLContext *ctx)
+GLuint QGL2GradientCache::getBuffer(const QGradient &gradient, qreal opacity, const QGLContext *ctx)
 {
     if (buffer_ctx && !qgl_share_reg()->checkSharing(buffer_ctx, ctx))
         cleanCache();
@@ -84,7 +84,7 @@ GLuint QGLGradientCache::getBuffer(const QGradient &gradient, qreal opacity, con
 }
 
 
-GLuint QGLGradientCache::addCacheElement(quint64 hash_val, const QGradient &gradient, qreal opacity)
+GLuint QGL2GradientCache::addCacheElement(quint64 hash_val, const QGradient &gradient, qreal opacity)
 {
     if (cache.size() == maxCacheSize()) {
         int elem_to_remove = qrand() % maxCacheSize();
@@ -129,7 +129,7 @@ static inline uint qtToGlColor(uint c)
 }
 
 //TODO: Let GL generate the texture using an FBO
-void QGLGradientCache::generateGradientColorTable(const QGradient& gradient, uint *colorTable, int size, qreal opacity) const
+void QGL2GradientCache::generateGradientColorTable(const QGradient& gradient, uint *colorTable, int size, qreal opacity) const
 {
     int pos = 0;
     QGradientStops s = gradient.stops();
diff --git a/src/opengl/gl2paintengineex/qglgradientcache_p.h b/src/opengl/gl2paintengineex/qglgradientcache_p.h
index 346ea13..6acaa00 100644
--- a/src/opengl/gl2paintengineex/qglgradientcache_p.h
+++ b/src/opengl/gl2paintengineex/qglgradientcache_p.h
@@ -54,7 +54,7 @@
 #include <QObject>
 #include <QtOpenGL>
 
-class QGLGradientCache : public QObject
+class QGL2GradientCache : public QObject
 {
     Q_OBJECT
     struct CacheInfo
@@ -71,7 +71,7 @@ class QGLGradientCache : public QObject
     typedef QMultiHash<quint64, CacheInfo> QGLGradientColorTableHash;
 
 public:
-    QGLGradientCache() : QObject(), buffer_ctx(0)
+    QGL2GradientCache() : QObject(), buffer_ctx(0)
     {
 /*
         connect(QGLSignalProxy::instance(),
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 1c0d7e0..9f2384d 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -240,7 +240,7 @@ void QGL2PaintEngineExPrivate::useSimpleShader()
 }
 
 
-Q_GLOBAL_STATIC(QGLGradientCache, qt_opengl_gradient_cache)
+Q_GLOBAL_STATIC(QGL2GradientCache, qt_opengl_gradient_cache)
 
 void QGL2PaintEngineExPrivate::updateBrushTexture()
 {
@@ -941,7 +941,7 @@ void QGL2PaintEngineEx::drawTextItem(const QPointF &p, const QTextItem &textItem
     Q_D(QGL2PaintEngineEx);
 
     ensureActive();
-    QOpenGLPaintEngineState *s = state();
+    QOpenGL2PaintEngineState *s = state();
 
     const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
 
@@ -967,7 +967,7 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(const QPointF &p, const QTextIte
     transferMode(TextDrawingMode);
 
     Q_Q(QGL2PaintEngineEx);
-    QOpenGLPaintEngineState *s = q->state();
+    QOpenGL2PaintEngineState *s = q->state();
 
     QVarLengthArray<QFixedPoint> positions;
     QVarLengthArray<glyph_t> glyphs;
@@ -1364,9 +1364,9 @@ void QGL2PaintEngineEx::setState(QPainterState *new_state)
 
     Q_D(QGL2PaintEngineEx);
 
-    QOpenGLPaintEngineState *s = static_cast<QOpenGLPaintEngineState *>(new_state);
+    QOpenGL2PaintEngineState *s = static_cast<QOpenGL2PaintEngineState *>(new_state);
 
-    QOpenGLPaintEngineState *old_state = state();
+    QOpenGL2PaintEngineState *old_state = state();
     const bool needsDepthClipUpdate = !old_state
             || s->clipEnabled != old_state->clipEnabled
             || (s->clipEnabled && s->clipRegion != old_state->clipRegion);
@@ -1386,28 +1386,28 @@ void QGL2PaintEngineEx::setState(QPainterState *new_state)
 
 QPainterState *QGL2PaintEngineEx::createState(QPainterState *orig) const
 {
-    QOpenGLPaintEngineState *s;
+    QOpenGL2PaintEngineState *s;
     if (!orig)
-        s = new QOpenGLPaintEngineState();
+        s = new QOpenGL2PaintEngineState();
     else
-        s = new QOpenGLPaintEngineState(*static_cast<QOpenGLPaintEngineState *>(orig));
+        s = new QOpenGL2PaintEngineState(*static_cast<QOpenGL2PaintEngineState *>(orig));
 
     return s;
 }
 
-QOpenGLPaintEngineState::QOpenGLPaintEngineState(QOpenGLPaintEngineState &other)
+QOpenGL2PaintEngineState::QOpenGL2PaintEngineState(QOpenGL2PaintEngineState &other)
     : QPainterState(other)
 {
     clipRegion = other.clipRegion;
     hasClipping = other.hasClipping;
 }
 
-QOpenGLPaintEngineState::QOpenGLPaintEngineState()
+QOpenGL2PaintEngineState::QOpenGL2PaintEngineState()
 {
     hasClipping = false;
 }
 
-QOpenGLPaintEngineState::~QOpenGLPaintEngineState()
+QOpenGL2PaintEngineState::~QOpenGL2PaintEngineState()
 {
 }
 
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
index b31f685..76a4fe0 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
@@ -58,12 +58,12 @@
 class QGL2PaintEngineExPrivate;
 
 
-class QOpenGLPaintEngineState : public QPainterState
+class QOpenGL2PaintEngineState : public QPainterState
 {
 public:
-    QOpenGLPaintEngineState(QOpenGLPaintEngineState &other);
-    QOpenGLPaintEngineState();
-    ~QOpenGLPaintEngineState();
+    QOpenGL2PaintEngineState(QOpenGL2PaintEngineState &other);
+    QOpenGL2PaintEngineState();
+    ~QOpenGL2PaintEngineState();
 
     QRegion clipRegion;
     bool hasClipping;
@@ -107,11 +107,11 @@ public:
     // State stuff is just for clipping and ripped off from QGLPaintEngine
     void setState(QPainterState *s);
     QPainterState *createState(QPainterState *orig) const;
-    inline QOpenGLPaintEngineState *state() {
-        return static_cast<QOpenGLPaintEngineState *>(QPaintEngineEx::state());
+    inline QOpenGL2PaintEngineState *state() {
+        return static_cast<QOpenGL2PaintEngineState *>(QPaintEngineEx::state());
     }
-    inline const QOpenGLPaintEngineState *state() const {
-        return static_cast<const QOpenGLPaintEngineState *>(QPaintEngineEx::state());
+    inline const QOpenGL2PaintEngineState *state() const {
+        return static_cast<const QOpenGL2PaintEngineState *>(QPaintEngineEx::state());
     }
     void updateClipRegion(const QRegion &clipRegion, Qt::ClipOperation op);
 
diff --git a/src/opengl/opengl.pro b/src/opengl/opengl.pro
index cfa9e4f..7eb2503 100644
--- a/src/opengl/opengl.pro
+++ b/src/opengl/opengl.pro
@@ -37,24 +37,21 @@ SOURCES	+= qgl.cpp \
            qglpixmapfilter.cpp \
            qglshaderprogram.cpp
 
-#!contains(QT_CONFIG, opengles2) {
-#    HEADERS += qpaintengine_opengl_p.h
-#    SOURCES += qpaintengine_opengl.cpp
-#}
+!contains(QT_CONFIG, opengles2) {
+    HEADERS += qpaintengine_opengl_p.h
+    SOURCES += qpaintengine_opengl.cpp
+}
 
-#contains(QT_CONFIG, opengles2) {
-    SOURCES +=  gl2paintengineex/qglgradientcache.cpp \
-                gl2paintengineex/qglengineshadermanager.cpp \
-                gl2paintengineex/qgl2pexvertexarray.cpp \
-                gl2paintengineex/qpaintengineex_opengl2.cpp
-
-    HEADERS +=  gl2paintengineex/qglgradientcache_p.h \
-                gl2paintengineex/qglengineshadermanager_p.h \
-                gl2paintengineex/qgl2pexvertexarray_p.h \
-                gl2paintengineex/qpaintengineex_opengl2_p.h \
-                gl2paintengineex/qglengineshadersource_p.h
-#}
+SOURCES +=  gl2paintengineex/qglgradientcache.cpp \
+            gl2paintengineex/qglengineshadermanager.cpp \
+            gl2paintengineex/qgl2pexvertexarray.cpp \
+            gl2paintengineex/qpaintengineex_opengl2.cpp
 
+HEADERS +=  gl2paintengineex/qglgradientcache_p.h \
+            gl2paintengineex/qglengineshadermanager_p.h \
+            gl2paintengineex/qgl2pexvertexarray_p.h \
+            gl2paintengineex/qpaintengineex_opengl2_p.h \
+            gl2paintengineex/qglengineshadersource_p.h
 
 x11 {
     contains(QT_CONFIG, opengles1)|contains(QT_CONFIG, opengles1cl)|contains(QT_CONFIG, opengles2) {
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index ccb6080..779ed9a 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -65,9 +65,9 @@
 #include "qimage.h"
 #include "qgl_p.h"
 
-#if 1 || defined(QT_OPENGL_ES_2)
 #include "gl2paintengineex/qpaintengineex_opengl2_p.h"
-#else
+
+#ifndef QT_OPENGL_ES_2
 #include <private/qpaintengine_opengl_p.h>
 #endif
 
@@ -2125,9 +2125,6 @@ void QGLContext::deleteTexture(QMacCompatGLuint id)
 }
 #endif
 
-// qpaintengine_opengl.cpp
-#if !defined(QT_OPENGL_ES_2)
-//extern void qt_add_rect_to_array(const QRectF &r, q_vertexType *array);
 void qt_add_rect_to_array(const QRectF &r, q_vertexType *array)
 {
     qreal left = r.left();
@@ -2145,9 +2142,17 @@ void qt_add_rect_to_array(const QRectF &r, q_vertexType *array)
     array[7] = f2vt(bottom);
 }
 
-#else
-void qt_add_rect_to_array(const QRectF &r, q_vertexType *array) {};
-#endif
+void qt_add_texcoords_to_array(qreal x1, qreal y1, qreal x2, qreal y2, q_vertexType *array)
+{
+    array[0] = f2vt(x1);
+    array[1] = f2vt(y1);
+    array[2] = f2vt(x2);
+    array[3] = f2vt(y1);
+    array[4] = f2vt(x2);
+    array[5] = f2vt(y2);
+    array[6] = f2vt(x1);
+    array[7] = f2vt(y2);
+}
 
 static void qDrawTextureRect(const QRectF &target, GLint textureWidth, GLint textureHeight, GLenum textureTarget)
 {
@@ -4154,9 +4159,9 @@ void QGLWidget::drawTexture(const QPointF &point, QMacCompatGLuint textureId, QM
 }
 #endif
 
-#if 1 || defined(QT_OPENGL_ES_2)
-Q_GLOBAL_STATIC(QGL2PaintEngineEx, qt_gl_engine)
-#else
+Q_GLOBAL_STATIC(QGL2PaintEngineEx, qt_gl_2_engine)
+
+#ifndef QT_OPENGL_ES_2
 Q_GLOBAL_STATIC(QOpenGLPaintEngine, qt_gl_engine)
 #endif
 
@@ -4179,7 +4184,11 @@ Q_OPENGL_EXPORT QPaintEngine* qt_qgl_paint_engine()
 */
 QPaintEngine *QGLWidget::paintEngine() const
 {
-    return qt_gl_engine();
+#ifndef QT_OPENGL_ES_2
+    if (!qt_gl_preferGL2Engine())
+        return qt_gl_engine();
+#endif
+    return qt_gl_2_engine();
 }
 
 #ifdef QT3_SUPPORT
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index f7b9392..1513ee8 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -419,6 +419,17 @@ extern QOpenGLPaintEngine* qt_qgl_paint_engine();
 extern EGLDisplay qt_qgl_egl_display();
 #endif
 
+inline bool qt_gl_preferGL2Engine()
+{
+#if defined(QT_OPENGL_ES_2)
+    return true;
+#else
+    QGLFormat::OpenGLVersionFlags flags = QGLFormat::openGLVersionFlags();
+    bool hasOpenGL2 = (flags & QGLFormat::OpenGL_Version_2_0);
+    return hasOpenGL2 && qgetenv("QT_GL_NO_OPENGL2ENGINE").isEmpty();
+#endif
+}
+
 inline GLenum qt_gl_preferredTextureFormat()
 {
     return QSysInfo::ByteOrder == QSysInfo::BigEndian ? GL_RGBA : GL_BGRA;
@@ -426,16 +437,16 @@ inline GLenum qt_gl_preferredTextureFormat()
 
 inline GLenum qt_gl_preferredTextureTarget()
 {
-#if 1 || defined(QT_OPENGL_ES_2)
+#if defined(QT_OPENGL_ES_2)
     return GL_TEXTURE_2D;
 #else
     return (QGLExtensions::glExtensions & QGLExtensions::TextureRectangle)
+           && !qt_gl_preferGL2Engine()
            ? GL_TEXTURE_RECTANGLE_NV
            : GL_TEXTURE_2D;
 #endif
 }
 
-
 QT_END_NAMESPACE
 
 #endif // QGL_P_H
diff --git a/src/opengl/qglframebufferobject.cpp b/src/opengl/qglframebufferobject.cpp
index aa5dfc5..87e0dda 100644
--- a/src/opengl/qglframebufferobject.cpp
+++ b/src/opengl/qglframebufferobject.cpp
@@ -43,11 +43,12 @@
 
 #include <qdebug.h>
 #include <private/qgl_p.h>
-#if 1 || defined(QT_OPENGL_ES_2)
 #include <private/qpaintengineex_opengl2_p.h>
-#else
+
+#ifndef QT_OPENGL_ES_2
 #include <private/qpaintengine_opengl_p.h>
 #endif
+
 #include <qglframebufferobject.h>
 #include <qlibrary.h>
 #include <qimage.h>
@@ -896,17 +897,20 @@ QImage QGLFramebufferObject::toImage() const
     return image;
 }
 
-#if 1 || defined(QT_OPENGL_ES_2)
-Q_GLOBAL_STATIC(QGL2PaintEngineEx, qt_buffer_paintengine)
-#else
-Q_GLOBAL_STATIC(QOpenGLPaintEngine, qt_buffer_paintengine)
+Q_GLOBAL_STATIC(QGL2PaintEngineEx, qt_buffer_2_engine)
+
+#ifndef QT_OPENGL_ES_2
+Q_GLOBAL_STATIC(QOpenGLPaintEngine, qt_buffer_engine)
 #endif
 
 /*! \reimp */
 QPaintEngine *QGLFramebufferObject::paintEngine() const
 {
 #if !defined(QT_OPENGL_ES_2)
-    return qt_buffer_paintengine();
+    if (qt_gl_preferGL2Engine())
+        return qt_buffer_2_engine();
+    else
+        return qt_buffer_engine();
 #else
     return 0;
 #endif
diff --git a/src/opengl/qglpixelbuffer.cpp b/src/opengl/qglpixelbuffer.cpp
index 6a207c8..cb24177 100644
--- a/src/opengl/qglpixelbuffer.cpp
+++ b/src/opengl/qglpixelbuffer.cpp
@@ -81,15 +81,15 @@
 #include <private/qglpixelbuffer_p.h>
 #include <qimage.h>
 
-#if 1 || defined(QT_OPENGL_ES_2)
 #include <private/qpaintengineex_opengl2_p.h>
-#else
+
+#ifndef QT_OPENGL_ES_2
 #include <private/qpaintengine_opengl_p.h>
 #endif
 
 QT_BEGIN_NAMESPACE
 
-#if 0 && !defined(QT_OPENGL_ES_2)
+#if !defined(QT_OPENGL_ES_2)
 extern void qgl_cleanup_glyph_cache(QGLContext *);
 #else
 void qgl_cleanup_glyph_cache(QGLContext *) {}
@@ -365,17 +365,20 @@ bool QGLPixelBuffer::isValid() const
     return !d->invalid;
 }
 
-#if 1 || defined(QT_OPENGL_ES_2)
-Q_GLOBAL_STATIC(QGL2PaintEngineEx, qt_buffer_paintengine)
-#else
-Q_GLOBAL_STATIC(QOpenGLPaintEngine, qt_buffer_paintengine)
+Q_GLOBAL_STATIC(QGL2PaintEngineEx, qt_buffer_2_engine)
+
+#ifndef QT_OPENGL_ES_2
+Q_GLOBAL_STATIC(QOpenGLPaintEngine, qt_buffer_engine)
 #endif
 
 /*! \reimp */
 QPaintEngine *QGLPixelBuffer::paintEngine() const
 {
 #if !defined(QT_OPENGL_ES_2)
-    return qt_buffer_paintengine();
+    if (qt_gl_preferGL2Engine())
+        return qt_buffer_2_engine();
+    else
+        return qt_buffer_engine();
 #else
     return 0;
 #endif
diff --git a/src/opengl/qglpixmapfilter.cpp b/src/opengl/qglpixmapfilter.cpp
index 5d4d5bf..eb3298b 100644
--- a/src/opengl/qglpixmapfilter.cpp
+++ b/src/opengl/qglpixmapfilter.cpp
@@ -116,21 +116,8 @@ QPixmapFilter *QGLContextPrivate::createPixmapFilter(int type) const
     return 0;
 }
 
-#if !defined(QT_OPENGL_ES_2)
 extern void qt_add_rect_to_array(const QRectF &r, q_vertexType *array);
-//extern void qt_add_texcoords_to_array(qreal x1, qreal y1, qreal x2, qreal y2, q_vertexType *array);
-void qt_add_texcoords_to_array(qreal x1, qreal y1, qreal x2, qreal y2, q_vertexType *array)
-{
-    array[0] = f2vt(x1);
-    array[1] = f2vt(y1);
-    array[2] = f2vt(x2);
-    array[3] = f2vt(y1);
-    array[4] = f2vt(x2);
-    array[5] = f2vt(y2);
-    array[6] = f2vt(x1);
-    array[7] = f2vt(y2);
-}
-#endif
+extern void qt_add_texcoords_to_array(qreal x1, qreal y1, qreal x2, qreal y2, q_vertexType *array);
 
 static void qgl_drawTexture(const QRectF &rect, int tx_width, int tx_height, const QRectF & src)
 {
diff --git a/src/opengl/qpaintengine_opengl.cpp b/src/opengl/qpaintengine_opengl.cpp
index 612168e..9197ebc 100644
--- a/src/opengl/qpaintengine_opengl.cpp
+++ b/src/opengl/qpaintengine_opengl.cpp
@@ -123,35 +123,6 @@ struct QT_PointF {
     qreal y;
 };
 
-void qt_add_rect_to_array(const QRectF &r, q_vertexType *array)
-{
-    qreal left = r.left();
-    qreal right = r.right();
-    qreal top = r.top();
-    qreal bottom = r.bottom();
-
-    array[0] = f2vt(left);
-    array[1] = f2vt(top);
-    array[2] = f2vt(right);
-    array[3] = f2vt(top);
-    array[4] = f2vt(right);
-    array[5] = f2vt(bottom);
-    array[6] = f2vt(left);
-    array[7] = f2vt(bottom);
-}
-
-void qt_add_texcoords_to_array(qreal x1, qreal y1, qreal x2, qreal y2, q_vertexType *array)
-{
-    array[0] = f2vt(x1);
-    array[1] = f2vt(y1);
-    array[2] = f2vt(x2);
-    array[3] = f2vt(y1);
-    array[4] = f2vt(x2);
-    array[5] = f2vt(y2);
-    array[6] = f2vt(x1);
-    array[7] = f2vt(y2);
-}
-
 struct QGLTrapezoid
 {
     QGLTrapezoid()
@@ -3124,6 +3095,9 @@ QGLTrapezoidMaskGenerator::QGLTrapezoidMaskGenerator(const QPainterPath &path, c
 {
 }
 
+extern void qt_add_rect_to_array(const QRectF &r, q_vertexType *array);
+extern void qt_add_texcoords_to_array(qreal x1, qreal y1, qreal x2, qreal y2, q_vertexType *array);
+
 void QGLTrapezoidMaskGenerator::drawMask(const QRect &rect)
 {
 #ifdef QT_OPENGL_ES
diff --git a/src/opengl/qpixmapdata_gl.cpp b/src/opengl/qpixmapdata_gl.cpp
index cb0b4d1..89e6749 100644
--- a/src/opengl/qpixmapdata_gl.cpp
+++ b/src/opengl/qpixmapdata_gl.cpp
@@ -49,11 +49,7 @@
 #include <private/qgl_p.h>
 #include <private/qdrawhelper_p.h>
 
-#if 1 || defined(QT_OPENGL_ES_2)
 #include <private/qpaintengineex_opengl2_p.h>
-#else
-#include <private/qpaintengine_opengl_p.h>
-#endif
 
 QT_BEGIN_NAMESPACE
 
diff --git a/src/opengl/qwindowsurface_gl.cpp b/src/opengl/qwindowsurface_gl.cpp
index 576da12..2f111f4 100644
--- a/src/opengl/qwindowsurface_gl.cpp
+++ b/src/opengl/qwindowsurface_gl.cpp
@@ -69,9 +69,10 @@
 
 #include <private/qglpixelbuffer_p.h>
 #include <private/qgraphicssystem_gl_p.h>
-#if 1 || defined(QT_OPENGL_ES_2)
+
 #include <private/qpaintengineex_opengl2_p.h>
-#else
+
+#ifndef QT_OPENGL_ES_2
 #include <private/qpaintengine_opengl_p.h>
 #endif
 
@@ -292,17 +293,20 @@ void QGLWindowSurface::hijackWindow(QWidget *widget)
     qDebug() << "hijackWindow() context created for" << widget << d_ptr->contexts.size();
 }
 
-#if 1 || defined(QT_OPENGL_ES_2)
-Q_GLOBAL_STATIC(QGL2PaintEngineEx, qt_gl_window_surface_paintengine)
-#else
-Q_GLOBAL_STATIC(QOpenGLPaintEngine, qt_gl_window_surface_paintengine)
+Q_GLOBAL_STATIC(QGL2PaintEngineEx, qt_gl_window_surface_2_engine)
+
+#ifndef QT_OPENGL_ES_2
+Q_GLOBAL_STATIC(QOpenGLPaintEngine, qt_gl_window_surface_engine)
 #endif
 
 /*! \reimp */
 QPaintEngine *QGLWindowSurface::paintEngine() const
 {
 #if !defined(QT_OPENGL_ES_2)
-    return qt_gl_window_surface_paintengine();
+    if (qt_gl_preferGL2Engine())
+        return qt_gl_window_surface_2_engine();
+    else
+        return qt_gl_window_surface_engine();
 #else
     return 0;
 #endif