Remove VBO caching and glDrawElements path in QStaticText

glDrawElements needs to be handled properly, using triangle strips
rather than triangle lists, so the code has been removed for now.
The VBO caching did not gain us any particular performance. We rather
cache the client-side buffers for the same speed-up but with less
clean-up complexity.

1 files changed, 43 insertions, 124 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index c66472c..18d67e9 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -1279,50 +1279,25 @@ void QGL2PaintEngineEx::drawTextItem(const QPointF &p, const QTextItem &textItem
     QPaintEngineEx::drawTextItem(p, ti);
 }
 
-#define QSTATICTEXT_USE_INDEXARRAY
+namespace {
 
-class QOpenGLStaticTextUserData: public QObject, public QStaticTextUserData
-{
-    Q_OBJECT
-public:
-    QOpenGLStaticTextUserData(QGLContext *glContext)
-        : QStaticTextUserData(OpenGLUserData),
-          vertexCoordVBOId(0), textureCoordVBOId(0), ctx(glContext)
-    {
-        connect(QGLSignalProxy::instance(),
-                SIGNAL(aboutToDestroyContext(const QGLContext*)),
-                SLOT(cleanupGLContextRefs(const QGLContext*)));
-    }
-
-    ~QOpenGLStaticTextUserData()
+    class QOpenGLStaticTextUserData: public QStaticTextUserData
     {
-        if (ctx != 0)
-            cleanupGLContextRefs(ctx);
-    }
-
-    QGLContext *ctx;
-    GLuint vertexCoordVBOId;
-    GLuint textureCoordVBOId;       
-
-#if defined(QSTATICTEXT_USE_INDEXARRAY)
-    QVector<GLuint> indices;
-#endif
+    public:
+        QOpenGLStaticTextUserData()
+            : QStaticTextUserData(OpenGLUserData)
+        {
+        }
 
-public Q_SLOTS:
-    void cleanupGLContextRefs(const QGLContext *context)
-    {
-        if (context == ctx) {
-            if (vertexCoordVBOId != 0)
-                glDeleteBuffers(1, &vertexCoordVBOId);
+        ~QOpenGLStaticTextUserData()
+        {
+        }
 
-            if (textureCoordVBOId != 0)
-                glDeleteBuffers(1, &textureCoordVBOId);
+        QGL2PEXVertexArray vertexCoordinateArray;
+        QGL2PEXVertexArray textureCoordinateArray;
+    };
 
-            vertexCoordVBOId = 0;
-            textureCoordVBOId = 0;
-        }
-    }
-};
+}
 
 void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyphType,
                                                 QStaticTextItem *staticTextItem,
@@ -1357,10 +1332,6 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
     GLfloat dx = 1.0 / cache->width();
     GLfloat dy = 1.0 / cache->height();
 
-#if defined(QSTATICTEXT_USE_INDEXARRAY)
-    QVector<GLuint> indices;
-#endif
-
     bool recreateVertexArrays = false;
     if (staticTextItem->userDataNeedsUpdate)
         recreateVertexArrays = true;
@@ -1368,93 +1339,49 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
         recreateVertexArrays = true;
     else if (staticTextItem->userData->type != QStaticTextUserData::OpenGLUserData)
         recreateVertexArrays = true;
-    else if (static_cast<QOpenGLStaticTextUserData *>(staticTextItem->userData)->ctx != ctx)
-        recreateVertexArrays = true;
-
-    if (recreateVertexArrays) {
-        vertexCoordinateArray.clear();
-        textureCoordinateArray.clear();
-
-#if defined(QSTATICTEXT_USE_INDEXARRAY)
-        QStaticTextUserData *uData = staticTextItem->userData;
-        QOpenGLStaticTextUserData *openGlUserData = uData != 0
-                                                    && uData->type == QStaticTextUserData::OpenGLUserData
-                                                    ? static_cast<QOpenGLStaticTextUserData *>(uData)
-                                                    : 0;
-        bool updateIndices = openGlUserData == 0
-                             || openGlUserData->indices.size() < staticTextItem->numGlyphs;
-        int j=0;
-#endif
-
-        for (int i=0; i<staticTextItem->numGlyphs; ++i) {
-            const QTextureGlyphCache::Coord &c = cache->coords.value(staticTextItem->glyphs[i]);
-            int x = staticTextItem->glyphPositions[i].x.toInt() + c.baseLineX - margin;
-            int y = staticTextItem->glyphPositions[i].y.toInt() - c.baseLineY - margin;
-
-            vertexCoordinateArray.addRect(QRectF(x, y, c.w, c.h));
-            textureCoordinateArray.addRect(QRectF(c.x*dx, c.y*dy, c.w * dx, c.h * dy));
-
-#if defined(QSTATICTEXT_USE_INDEXARRAY)
-            if (updateIndices) {
-                for (int k=0; k<6; ++k)
-                    indices.append(j++);
-            }
-#endif
-        }
 
-        if (staticTextItem->useBackendOptimizations) {
-            QOpenGLStaticTextUserData *userData =
-                    staticTextItem->userData != 0 && staticTextItem->userData->type == QStaticTextUserData::OpenGLUserData
-                        ? static_cast<QOpenGLStaticTextUserData *>(staticTextItem->userData)
-                        : new QOpenGLStaticTextUserData(ctx);
+    // Use global arrays by default
+    QGL2PEXVertexArray *vertexCoordinates = &vertexCoordinateArray;
+    QGL2PEXVertexArray *textureCoordinates = &textureCoordinateArray;
 
-            int vertexCoordinateArraySize = vertexCoordinateArray.vertexCount() * sizeof(QGLPoint);
-            if (userData->vertexCoordVBOId == 0)
-                glGenBuffers(1, &userData->vertexCoordVBOId);
-
-            int textureCoordinateArraySize = textureCoordinateArray.vertexCount() * sizeof(QGLPoint);
-            if (userData->textureCoordVBOId == 0)
-                glGenBuffers(1, &userData->textureCoordVBOId);
-
-            glBindBuffer(GL_ARRAY_BUFFER, userData->vertexCoordVBOId);
-            glBufferData(GL_ARRAY_BUFFER, vertexCoordinateArraySize,
-                         vertexCoordinateArray.data(), GL_STATIC_DRAW);
+    if (staticTextItem->useBackendOptimizations) {
+        QOpenGLStaticTextUserData *userData = 0;
 
-            glBindBuffer(GL_ARRAY_BUFFER, userData->textureCoordVBOId);
-            glBufferData(GL_ARRAY_BUFFER, textureCoordinateArraySize,
-                         textureCoordinateArray.data(), GL_STATIC_DRAW);
+        if (staticTextItem->userData == 0
+            || staticTextItem->userData->type != QStaticTextUserData::OpenGLUserData) {
 
-#if defined(QSTATICTEXT_USE_INDEXARRAY)
-            if (updateIndices)
-                userData->indices = indices;
-#endif
-
-            // If a new user data has been created, make sure we delete the old
+            userData = new QOpenGLStaticTextUserData();
             staticTextItem->setUserData(userData);
-            staticTextItem->userDataNeedsUpdate = false;            
 
         } else {
-            setVertexAttributePointer(QT_VERTEX_COORDS_ATTR, (GLfloat*)vertexCoordinateArray.data());
-            setVertexAttributePointer(QT_TEXTURE_COORDS_ATTR, (GLfloat*)textureCoordinateArray.data());
+            userData = static_cast<QOpenGLStaticTextUserData*>(staticTextItem->userData);
         }
+
+        // Use cache if backend optimizations is turned on
+        vertexCoordinates = &userData->vertexCoordinateArray;
+        textureCoordinates = &userData->textureCoordinateArray;
     }
-    if (staticTextItem->useBackendOptimizations) {
-        Q_ASSERT(staticTextItem->userData != 0);
-        Q_ASSERT(staticTextItem->userData->type == QStaticTextUserData::OpenGLUserData);
 
-        QOpenGLStaticTextUserData *userData = static_cast<QOpenGLStaticTextUserData *>(staticTextItem->userData);
 
-        glBindBuffer(GL_ARRAY_BUFFER, userData->vertexCoordVBOId);
-        glVertexAttribPointer(QT_VERTEX_COORDS_ATTR, 2, GL_FLOAT, GL_FALSE, 0, 0);
+    if (recreateVertexArrays) {
+        vertexCoordinates->clear();
+        textureCoordinates->clear();
 
-        glBindBuffer(GL_ARRAY_BUFFER, userData->textureCoordVBOId);
-        glVertexAttribPointer(QT_TEXTURE_COORDS_ATTR, 2, GL_FLOAT, GL_FALSE, 0, 0);
+        for (int i=0; i<staticTextItem->numGlyphs; ++i) {
+            const QTextureGlyphCache::Coord &c = cache->coords.value(staticTextItem->glyphs[i]);
+            int x = staticTextItem->glyphPositions[i].x.toInt() + c.baseLineX - margin;
+            int y = staticTextItem->glyphPositions[i].y.toInt() - c.baseLineY - margin;
 
-#if defined(QSTATICTEXT_USE_INDEXARRAY)
-        indices = userData->indices;
-#endif
+            vertexCoordinates->addRect(QRectF(x, y, c.w, c.h));
+            textureCoordinates->addRect(QRectF(c.x*dx, c.y*dy, c.w * dx, c.h * dy));
+        }
+
+        staticTextItem->userDataNeedsUpdate = false;
     }
 
+    setVertexAttributePointer(QT_VERTEX_COORDS_ATTR, (GLfloat*)vertexCoordinates->data());
+    setVertexAttributePointer(QT_TEXTURE_COORDS_ATTR, (GLfloat*)textureCoordinates->data());
+
     if (addOffset) {
         addOffset = false;
         matrixDirty = true;
@@ -1473,6 +1400,7 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
     QTransform old = s->matrix;
     if (includeMatrixInCache)
         s->matrix = QTransform();
+
     if (glyphType == QFontEngineGlyphCache::Raster_RGBMask) {
 
         // Subpixel antialiasing without gamma correction
@@ -1557,14 +1485,7 @@ void QGL2PaintEngineExPrivate::drawCachedGlyphs(QFontEngineGlyphCache::Type glyp
 
     shaderManager->currentProgram()->setUniformValue(location(QGLEngineShaderManager::MaskTexture), QT_MASK_TEXTURE_UNIT);
 
-#if defined(QSTATICTEXT_USE_INDEXARRAY)
-    glDrawElements(GL_TRIANGLES, 6 * staticTextItem->numGlyphs, GL_UNSIGNED_INT, indices.constData());
-#else
     glDrawArrays(GL_TRIANGLES, 0, 6 * staticTextItem->numGlyphs);
-#endif
-
-    // Reset bindings
-    glBindBuffer(GL_ARRAY_BUFFER, 0);
 
     if (includeMatrixInCache)
         s->matrix = old;
@@ -2191,5 +2112,3 @@ QOpenGL2PaintEngineState::~QOpenGL2PaintEngineState()
 }
 
 QT_END_NAMESPACE
-
-#include "qpaintengineex_opengl2.moc"