Fixed QGLWidget::renderText().

Fall back and use the GL 1 engine for the renderText() functions.
Getting it to work with the GL 2 engine is a futile effort.
Making it work with renderPixmap() in the GL 2 engine is not possible
at all, since software contexts in general do not support shader
programs.

Task-number: QTBUG-5002, QTBUG-6931
Reviewed-by: Kim
(cherry picked from commit 5394052c422f7087263ad6dc6d6a4448b4c4afba)

3 files changed, 13 insertions, 109 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 0a59cd8..6622e55 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -227,11 +227,6 @@ void QGLTextureGlyphCache::resizeTextureData(int width, int height)
 
     pex->transferMode(BrushDrawingMode);
 
-#ifndef QT_OPENGL_ES_2
-    if (pex->inRenderText)
-        glPushAttrib(GL_ENABLE_BIT | GL_VIEWPORT_BIT | GL_SCISSOR_BIT);
-#endif
-
     glDisable(GL_STENCIL_TEST);
     glDisable(GL_DEPTH_TEST);
     glDisable(GL_SCISSOR_TEST);
@@ -283,11 +278,6 @@ void QGLTextureGlyphCache::resizeTextureData(int width, int height)
 
     glViewport(0, 0, pex->width, pex->height);
     pex->updateClipScissorTest();
-
-#ifndef QT_OPENGL_ES_2
-    if (pex->inRenderText)
-        glPopAttrib();
-#endif
 }
 
 void QGLTextureGlyphCache::fillTexture(const Coord &c, glyph_t glyph)
@@ -984,20 +974,11 @@ void QGL2PaintEngineExPrivate::fill(const QVectorPath& path)
             // Pass when high bit is set, replace stencil value with 0
             glStencilFunc(GL_NOTEQUAL, 0, GL_STENCIL_HIGH_BIT);
         }
-
         prepareForDraw(currentBrush.isOpaque());
 
-        if (inRenderText)
-            prepareDepthRangeForRenderText();
-
         // Stencil the brush onto the dest buffer
         composite(vertexCoordinateArray.boundingRect());
-
-        if (inRenderText)
-            restoreDepthRangeForRenderText();
-
         glStencilMask(0);
-
         updateClipScissorTest();
     }
 }
@@ -1036,13 +1017,6 @@ void QGL2PaintEngineExPrivate::fillStencilWithVertexArray(const float *data,
     useSimpleShader();
     glEnable(GL_STENCIL_TEST); // For some reason, this has to happen _after_ the simple shader is use()'d
 
-#ifndef QT_OPENGL_ES_2
-    if (inRenderText) {
-        glPushAttrib(GL_ENABLE_BIT);
-        glDisable(GL_DEPTH_TEST);
-    }
-#endif
-
     if (mode == WindingFillMode) {
         Q_ASSERT(stops && !count);
         if (q->state()->clipTestEnabled) {
@@ -1105,12 +1079,6 @@ void QGL2PaintEngineExPrivate::fillStencilWithVertexArray(const float *data,
 
     // Enable color writes & disable stencil writes
     glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
-
-#ifndef QT_OPENGL_ES_2
-    if (inRenderText)
-        glPopAttrib();
-#endif
-
 }
 
 /*
@@ -1256,30 +1224,6 @@ void QGL2PaintEngineExPrivate::drawVertexArrays(const float *data, int *stops, i
     glDisableVertexAttribArray(QT_VERTEX_COORDS_ATTR);
 }
 
-void QGL2PaintEngineExPrivate::prepareDepthRangeForRenderText()
-{
-#ifndef QT_OPENGL_ES_2
-    // Get the z translation value from the model view matrix and
-    // transform it using the ortogonal projection with z-near = 0,
-    // and z-far = 1, which is used in QGLWidget::renderText()
-    GLdouble model[4][4];
-    glGetDoublev(GL_MODELVIEW_MATRIX, &model[0][0]);
-    float deviceZ = -2 * model[3][2] - 1;
-
-    glGetFloatv(GL_DEPTH_RANGE, depthRange);
-    float windowZ = depthRange[0] + (deviceZ + 1) * 0.5 * (depthRange[1] - depthRange[0]);
-
-    glDepthRange(windowZ, windowZ);
-#endif
-}
-
-void QGL2PaintEngineExPrivate::restoreDepthRangeForRenderText()
-{
-#ifndef QT_OPENGL_ES_2
-    glDepthRange(depthRange[0], depthRange[1]);
-#endif
-}
-
 /////////////////////////////////// Public Methods //////////////////////////////////////////
 
 QGL2PaintEngineEx::QGL2PaintEngineEx()
@@ -1297,10 +1241,7 @@ void QGL2PaintEngineEx::fill(const QVectorPath &path, const QBrush &brush)
 
     if (qbrush_style(brush) == Qt::NoBrush)
         return;
-
-    if (!d->inRenderText)
-        ensureActive();
-
+    ensureActive();
     d->setBrush(brush);
     d->fill(path);
 }
@@ -1518,8 +1459,7 @@ void QGL2PaintEngineEx::drawTextItem(const QPointF &p, const QTextItem &textItem
 {
     Q_D(QGL2PaintEngineEx);
 
-    if (!d->inRenderText)
-        ensureActive();
+    ensureActive();
     QOpenGL2PaintEngineState *s = state();
 
     const QTextItemInt &ti = static_cast<const QTextItemInt &>(textItem);
@@ -1538,7 +1478,7 @@ void QGL2PaintEngineEx::drawTextItem(const QPointF &p, const QTextItem &textItem
                                             ? QFontEngineGlyphCache::Type(ti.fontEngine->glyphFormat)
                                             : d->glyphCacheType;
 
-    if (d->inRenderText || txtype > QTransform::TxTranslate)
+    if (txtype > QTransform::TxTranslate)
         glyphType = QFontEngineGlyphCache::Raster_A8;
 
     if (glyphType == QFontEngineGlyphCache::Raster_RGBMask
@@ -1580,8 +1520,6 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(const QPointF &p, QFontEngineGly
     if (cache->width() == 0 || cache->height() == 0)
         return;
 
-    if (inRenderText)
-        transferMode(BrushDrawingMode);
     transferMode(TextDrawingMode);
 
     int margin = cache->glyphMargin();
@@ -1617,9 +1555,6 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(const QPointF &p, QFontEngineGly
     QBrush pensBrush = q->state()->pen.brush();
     setBrush(pensBrush);
 
-    if (inRenderText)
-        prepareDepthRangeForRenderText();
-
     if (glyphType == QFontEngineGlyphCache::Raster_RGBMask) {
 
         // Subpixel antialiasing without gamma correction
@@ -1704,9 +1639,6 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(const QPointF &p, QFontEngineGly
 
     shaderManager->currentProgram()->setUniformValue(location(QGLEngineShaderManager::MaskTexture), QT_MASK_TEXTURE_UNIT);
     glDrawArrays(GL_TRIANGLES, 0, 6 * glyphs.size());
-
-    if (inRenderText)
-        restoreDepthRangeForRenderText();
 }
 
 void QGL2PaintEngineEx::drawPixmaps(const QDrawPixmaps::Data *drawingData, int dataCount, const QPixmap &pixmap, QDrawPixmaps::DrawingHints hints)
@@ -1854,11 +1786,9 @@ bool QGL2PaintEngineEx::begin(QPaintDevice *pdev)
 
     d->shaderManager = new QGLEngineShaderManager(d->ctx);
 
-    if (!d->inRenderText) {
-        glDisable(GL_STENCIL_TEST);
-        glDisable(GL_DEPTH_TEST);
-        glDisable(GL_SCISSOR_TEST);
-    }
+    glDisable(GL_STENCIL_TEST);
+    glDisable(GL_DEPTH_TEST);
+    glDisable(GL_SCISSOR_TEST);
 
 #if !defined(QT_OPENGL_ES_2)
     glDisable(GL_MULTISAMPLE);
@@ -2298,12 +2228,6 @@ QPainterState *QGL2PaintEngineEx::createState(QPainterState *orig) const
     return s;
 }
 
-void QGL2PaintEngineEx::setRenderTextActive(bool active)
-{
-    Q_D(QGL2PaintEngineEx);
-    d->inRenderText = active;
-}
-
 QOpenGL2PaintEngineState::QOpenGL2PaintEngineState(QOpenGL2PaintEngineState &other)
     : QPainterState(other)
 {
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
index ae1f2fc..8562678 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
@@ -168,8 +168,7 @@ public:
             ctx(0),
             useSystemClip(true),
             addOffset(false),
-            inverseScale(1),
-            inRenderText(false)
+            inverseScale(1)
     { }
 
     ~QGL2PaintEngineExPrivate();
@@ -215,10 +214,6 @@ public:
         return shaderManager->getUniformLocation(uniform);
     }
 
-
-    void prepareDepthRangeForRenderText();
-    void restoreDepthRangeForRenderText();
-
     void clearClip(uint value);
     void writeClip(const QVectorPath &path, uint value);
     void resetClipIfNeeded();
@@ -228,7 +223,6 @@ public:
     void regenerateClip();
     void systemStateChanged();
 
-
     static QGLEngineShaderManager* shaderManagerForEngine(QGL2PaintEngineEx *engine) { return engine->d_func()->shaderManager; }
     static QGL2PaintEngineExPrivate *getData(QGL2PaintEngineEx *engine) { return engine->d_func(); }
     static void cleanupVectorPath(QPaintEngineEx *engine, void *data);
@@ -273,7 +267,6 @@ public:
     GLuint lastTextureUsed;
 
     bool needsSync;
-    bool inRenderText;
     bool multisamplingAlwaysEnabled;
 
     GLfloat depthRange[2];
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 49d0959..ea2ea63 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -4378,9 +4378,9 @@ void QGLWidget::renderText(int x, int y, const QString &str, const QFont &font,
     int height = d->glcx->device()->height();
     bool auto_swap = autoBufferSwap();
 
+    QPaintEngine::Type oldEngineType = qgl_engine_selector()->preferredPaintEngine();
+    qgl_engine_selector()->setPreferredPaintEngine(QPaintEngine::OpenGL);
     QPaintEngine *engine = paintEngine();
-    if (engine->type() == QPaintEngine::OpenGL2)
-        static_cast<QGL2PaintEngineEx *>(engine)->setRenderTextActive(true);
     QPainter *p;
     bool reuse_painter = false;
     if (engine->isActive()) {
@@ -4400,11 +4400,6 @@ void QGLWidget::renderText(int x, int y, const QString &str, const QFont &font,
         setAutoBufferSwap(false);
         // disable glClear() as a result of QPainter::begin()
         d->disable_clear_on_painter_begin = true;
-        if (engine->type() == QPaintEngine::OpenGL2) {
-            qt_save_gl_state();
-            glMatrixMode(GL_MODELVIEW);
-            glLoadIdentity();
-        }
         p = new QPainter(this);
     }
 
@@ -4428,11 +4423,8 @@ void QGLWidget::renderText(int x, int y, const QString &str, const QFont &font,
         delete p;
         setAutoBufferSwap(auto_swap);
         d->disable_clear_on_painter_begin = false;
-        if (engine->type() == QPaintEngine::OpenGL2)
-            qt_restore_gl_state();
     }
-    if (engine->type() == QPaintEngine::OpenGL2)
-        static_cast<QGL2PaintEngineEx *>(engine)->setRenderTextActive(false);
+    qgl_engine_selector()->setPreferredPaintEngine(oldEngineType);
 #else // QT_OPENGL_ES
     Q_UNUSED(x);
     Q_UNUSED(y);
@@ -4480,9 +4472,9 @@ void QGLWidget::renderText(double x, double y, double z, const QString &str, con
                 &win_x, &win_y, &win_z);
     win_y = height - win_y; // y is inverted
 
+    QPaintEngine::Type oldEngineType = qgl_engine_selector()->preferredPaintEngine();
+    qgl_engine_selector()->setPreferredPaintEngine(QPaintEngine::OpenGL);
     QPaintEngine *engine = paintEngine();
-    if (engine->type() == QPaintEngine::OpenGL2)
-        static_cast<QGL2PaintEngineEx *>(engine)->setRenderTextActive(true);
     QPainter *p;
     bool reuse_painter = false;
     bool use_depth_testing = glIsEnabled(GL_DEPTH_TEST);
@@ -4496,8 +4488,6 @@ void QGLWidget::renderText(double x, double y, double z, const QString &str, con
         setAutoBufferSwap(false);
         // disable glClear() as a result of QPainter::begin()
         d->disable_clear_on_painter_begin = true;
-        if (engine->type() == QPaintEngine::OpenGL2)
-            qt_save_gl_state();
         p = new QPainter(this);
     }
 
@@ -4526,13 +4516,10 @@ void QGLWidget::renderText(double x, double y, double z, const QString &str, con
     } else {
         p->end();
         delete p;
-        if (engine->type() == QPaintEngine::OpenGL2)
-            qt_restore_gl_state();
         setAutoBufferSwap(auto_swap);
         d->disable_clear_on_painter_begin = false;
     }
-    if (engine->type() == QPaintEngine::OpenGL2)
-        static_cast<QGL2PaintEngineEx *>(engine)->setRenderTextActive(false);
+    qgl_engine_selector()->setPreferredPaintEngine(oldEngineType);
 #else // QT_OPENGL_ES
     Q_UNUSED(x);
     Q_UNUSED(y);