Added caching of vectorpaths to the GL paint engine.

The first time a path is drawn we call makeCachable on the path, which
means that if it is drawn again, we start caching it. This is a bit of
a trick to avoid caching paths that are drawn once and discared while
at the same time cache paths that are reused automatically.

The GL engine owns the vertex information and is responsible for cleaning
it up. If the vectorpath is destroyed first, it will call the cleanup function.
if the engine dies first, we still require some hooks to clean up the cache
in the path. More to come. When VBO's are used, these will be a leaked if the
path is destroyed after the engine.

Reviewed-by: Samuel

3 files changed, 116 insertions, 5 deletions

diff --git a/src/opengl/gl2paintengineex/qgl2pexvertexarray_p.h b/src/opengl/gl2paintengineex/qgl2pexvertexarray_p.h
index 03aec17..98eaa91 100644
--- a/src/opengl/gl2paintengineex/qgl2pexvertexarray_p.h
+++ b/src/opengl/gl2paintengineex/qgl2pexvertexarray_p.h
@@ -112,6 +112,8 @@ public:
     int stopCount() const { return vertexArrayStops.size(); }
     QGLRect         boundingRect() const;
 
+    int vertexCount() const { return vertexArray.size(); }
+
     void lineToArray(const GLfloat x, const GLfloat y);
 
 private:
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index 6a708b4..3fce384 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -62,6 +62,8 @@
     and use the correct program when we really need it.
 */
 
+// #define QT_OPENGL_CACHE_AS_VBOS
+
 #include "qpaintengineex_opengl2_p.h"
 
 #include <string.h> //for memcpy
@@ -344,6 +346,13 @@ extern QImage qt_imageForBrush(int brushStyle, bool invert);
 QGL2PaintEngineExPrivate::~QGL2PaintEngineExPrivate()
 {
     delete shaderManager;
+
+    while (pathCaches.size()) {
+        QVectorPath::CacheEntry *e = *(pathCaches.constBegin());
+        e->cleanup(e->engine, e->data);
+        e->data = 0;
+        e->engine = 0;
+    }
 }
 
 void QGL2PaintEngineExPrivate::updateTextureFilter(GLenum target, GLenum wrapMode, bool smoothPixmapTransform, GLuint id)
@@ -846,6 +855,30 @@ void QGL2PaintEngineExPrivate::transferMode(EngineMode newMode)
     mode = newMode;
 }
 
+struct QGL2PEVectorPathCache
+{
+#ifdef QT_OPENGL_CACHE_AS_VBOS
+    GLuint vbo;
+#else
+    float *vertices;
+#endif
+    int vertexCount;
+    GLenum primitiveType;
+    qreal iscale;
+};
+
+void qopengl2paintengine_cleanup_vectorpath(QPaintEngineEx *engine, void *data)
+{
+    QGL2PEVectorPathCache *c = (QGL2PEVectorPathCache *) data;
+#ifdef QT_OPENGL_CACHE_AS_VBOS
+    QGL2PaintEngineExPrivate *d = QGL2PaintEngineExPrivate::getData((QGL2PaintEngineEx *) engine);
+    d->unusedVBOSToClean << c->vbo;
+#else
+    qFree(c->vertices);
+#endif
+    delete c;
+}
+
 // Assumes everything is configured for the brush you want to use
 void QGL2PaintEngineExPrivate::fill(const QVectorPath& path)
 {
@@ -863,10 +896,74 @@ void QGL2PaintEngineExPrivate::fill(const QVectorPath& path)
         prepareForDraw(currentBrush->isOpaque());
         composite(rect);
     } else if (path.isConvex()) {
-        vertexCoordinateArray.clear();
-        vertexCoordinateArray.addPath(path, inverseScale, false);
-        prepareForDraw(currentBrush->isOpaque());
-        drawVertexArrays(vertexCoordinateArray, GL_TRIANGLE_FAN);
+
+        if (path.isCacheable()) {
+            QVectorPath::CacheEntry *data = path.lookupCacheData(q);
+            QGL2PEVectorPathCache *cache;
+
+            if (data) {
+                cache = (QGL2PEVectorPathCache *) data->data;
+                // Check if scale factor is exceeded for curved paths and generate curves if so...
+                if (path.isCurved()) {
+                    qreal scaleFactor = cache->iscale / inverseScale;
+                    if (scaleFactor < 0.5 || scaleFactor > 2.0) {
+#ifdef QT_OPENGL_CACHE_AS_VBOS
+                        glDeleteBuffers(1, &cache->vbo);
+                        cache->vbo = 0;
+#else
+                        qFree(cache->vertices);
+#endif
+                        cache->vertexCount = 0;
+                    }
+                }
+            } else {
+                cache = new QGL2PEVectorPathCache;
+                cache->vertexCount = 0;
+                data = const_cast<QVectorPath &>(path).addCacheData(q, cache, qopengl2paintengine_cleanup_vectorpath);
+            }
+
+            // Flatten the path at the current scale factor and fill it into the cache struct.
+            if (!cache->vertexCount) {
+                vertexCoordinateArray.clear();
+                vertexCoordinateArray.addPath(path, inverseScale, false);
+                int vertexCount = vertexCoordinateArray.vertexCount();
+                int floatSizeInBytes = vertexCount * 2 * sizeof(float);
+                cache->vertexCount = vertexCount;
+                cache->primitiveType = GL_TRIANGLE_FAN;
+                cache->iscale = inverseScale;               
+#ifdef QT_OPENGL_CACHE_AS_VBOS
+                glGenBuffers(1, &cache->vbo);
+                glBindBuffer(GL_ARRAY_BUFFER, cache->vbo);
+                glBufferData(GL_ARRAY_BUFFER, floatSizeInBytes, vertexCoordinateArray.data(), GL_STATIC_DRAW);
+#else
+                cache->vertices = (float *) qMalloc(floatSizeInBytes);
+                memcpy(cache->vertices, vertexCoordinateArray.data(), floatSizeInBytes);
+#endif
+            }
+
+            prepareForDraw(currentBrush->isOpaque());
+            glEnableVertexAttribArray(QT_VERTEX_COORDS_ATTR);
+#ifdef QT_OPENGL_CACHE_AS_VBOS
+            glBindBuffer(GL_ARRAY_BUFFER, cache->vbo);
+            glVertexAttribPointer(QT_VERTEX_COORDS_ATTR, 2, GL_FLOAT, false, 0, 0);
+#else
+            glVertexAttribPointer(QT_VERTEX_COORDS_ATTR, 2, GL_FLOAT, false, 0, cache->vertices);
+#endif
+            glDrawArrays(cache->primitiveType, 0, cache->vertexCount);
+
+        } else {
+      //        printf(" - Marking path as cachable...\n");
+            // Tag it for later so that if the same path is drawn twice, it is assumed to be static and thus cachable
+            // ### Remove before release...
+            static bool do_vectorpath_cache = qgetenv("QT_OPENGL_NO_PATH_CACHE").isEmpty();
+            if (do_vectorpath_cache)
+                path.makeCacheable();
+            vertexCoordinateArray.clear();
+            vertexCoordinateArray.addPath(path, inverseScale, false);
+            prepareForDraw(currentBrush->isOpaque());
+            drawVertexArrays(vertexCoordinateArray, GL_TRIANGLE_FAN);
+        }
+
     } else {
         // The path is too complicated & needs the stencil technique
         vertexCoordinateArray.clear();
@@ -1756,7 +1853,8 @@ bool QGL2PaintEngineEx::begin(QPaintDevice *pdev)
     d->device->beginPaint();
 
 #if !defined(QT_OPENGL_ES_2)
-    bool success = qt_resolve_version_2_0_functions(d->ctx);
+    bool success = qt_resolve_version_2_0_functions(d->ctx)
+                   && qt_resolve_buffer_extensions(d->ctx);
     Q_ASSERT(success);
     Q_UNUSED(success);
 #endif
@@ -1817,6 +1915,13 @@ bool QGL2PaintEngineEx::end()
     delete d->shaderManager;
     d->shaderManager = 0;
 
+#ifdef QT_OPENGL_CACHE_AS_VBOS
+    if (!d->unusedVBOSToClean.isEmpty()) {
+        glDeleteBuffers(d->unusedVBOSToClean.size(), d->unusedVBOSToClean.constData());
+        d->unusedVBOSToClean.clear();
+    }
+#endif
+
     return false;
 }
 
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
index b554f6d..0084476 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2_p.h
@@ -221,6 +221,7 @@ public:
     void restoreDepthRangeForRenderText();
 
     static QGLEngineShaderManager* shaderManagerForEngine(QGL2PaintEngineEx *engine) { return engine->d_func()->shaderManager; }
+    static QGL2PaintEngineExPrivate *getData(QGL2PaintEngineEx *engine) { return engine->d_func(); }
 
     QGL2PaintEngineEx* q;
     QGLPaintDevice* device;
@@ -294,6 +295,9 @@ public:
     QScopedPointer<QPixmapFilter> fastBlurFilter;
     QScopedPointer<QPixmapFilter> dropShadowFilter;
     QScopedPointer<QPixmapFilter> fastDropShadowFilter;
+
+    QSet<QVectorPath::CacheEntry *> pathCaches;
+    QVector<GLuint> unusedVBOSToClean;
 };
 
 QT_END_NAMESPACE