Track which vertex attrib arrays are enabled in QGLContextPrivate

The GL2 engine (and probably Qt/3D) needs to track which vertex
attribute arrays are currently enabled and which are disabled. As
this is per-context state, the logical place to track this is in the
context and not in the paint engine.

This patch also makes the GL2 engine's shader manager enable/disable
the appropriate attribute arrays for a given shader program when it
is used.

Reviewed-By: Kim

6 files changed, 79 insertions, 5 deletions

diff --git a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
index d28d5f3..da33eb3 100644
--- a/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
+++ b/src/opengl/gl2paintengineex/qglengineshadermanager.cpp
@@ -505,7 +505,27 @@ QGLShaderProgram* QGLEngineShaderManager::currentProgram()
     if (currentShaderProg)
         return currentShaderProg->program;
     else
-        return simpleProgram();
+        return sharedShaders->simpleProgram();
+}
+
+void QGLEngineShaderManager::useSimpleProgram()
+{
+    sharedShaders->simpleProgram()->bind();
+    QGLContextPrivate* ctx_d = ctx->d_func();
+    ctx_d->setVertexAttribArrayEnabled(QT_VERTEX_COORDS_ATTR, true);
+    ctx_d->setVertexAttribArrayEnabled(QT_TEXTURE_COORDS_ATTR, false);
+    ctx_d->setVertexAttribArrayEnabled(QT_OPACITY_ATTR, false);
+    shaderProgNeedsChanging = true;
+}
+
+void QGLEngineShaderManager::useBlitProgram()
+{
+    sharedShaders->blitProgram()->bind();
+    QGLContextPrivate* ctx_d = ctx->d_func();
+    ctx_d->setVertexAttribArrayEnabled(QT_VERTEX_COORDS_ATTR, true);
+    ctx_d->setVertexAttribArrayEnabled(QT_TEXTURE_COORDS_ATTR, true);
+    ctx_d->setVertexAttribArrayEnabled(QT_OPACITY_ATTR, false);
+    shaderProgNeedsChanging = true;
 }
 
 QGLShaderProgram* QGLEngineShaderManager::simpleProgram()
@@ -716,6 +736,13 @@ bool QGLEngineShaderManager::useCorrectShaderProg()
             customSrcStage->setUniforms(currentShaderProg->program);
     }
 
+    // Make sure all the vertex attribute arrays the program uses are enabled (and the ones it
+    // doesn't use are disabled)
+    QGLContextPrivate* ctx_d = ctx->d_func();
+    ctx_d->setVertexAttribArrayEnabled(QT_VERTEX_COORDS_ATTR, true);
+    ctx_d->setVertexAttribArrayEnabled(QT_TEXTURE_COORDS_ATTR, currentShaderProg->useTextureCoords);
+    ctx_d->setVertexAttribArrayEnabled(QT_OPACITY_ATTR, currentShaderProg->useOpacityAttribute);
+
     shaderProgNeedsChanging = false;
     return true;
 }
diff --git a/src/opengl/gl2paintengineex/qglengineshadermanager_p.h b/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
index 1ec4cdc..a132e1b 100644
--- a/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
+++ b/src/opengl/gl2paintengineex/qglengineshadermanager_p.h
@@ -468,6 +468,9 @@ public:
     void setDirty(); // someone has manually changed the current shader program
     bool useCorrectShaderProg(); // returns true if the shader program needed to be changed
 
+    void useSimpleProgram();
+    void useBlitProgram();
+
     QGLShaderProgram* currentProgram(); // Returns pointer to the shader the manager has chosen
     QGLShaderProgram* simpleProgram(); // Used to draw into e.g. stencil buffers
     QGLShaderProgram* blitProgram(); // Used to blit a texture into the framebuffer
diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index d3a9547..0574c52 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -248,9 +248,8 @@ void QGLTextureGlyphCache::resizeTextureData(int width, int height)
     glVertexAttribPointer(QT_VERTEX_COORDS_ATTR, 2, GL_FLOAT, GL_FALSE, 0, vertexCoordinateArray);
     glVertexAttribPointer(QT_TEXTURE_COORDS_ATTR, 2, GL_FLOAT, GL_FALSE, 0, textureCoordinateArray);
 
-    pex->shaderManager->blitProgram()->bind();
+    pex->shaderManager->useBlitProgram();
     pex->shaderManager->blitProgram()->setUniformValue("imageTexture", QT_IMAGE_TEXTURE_UNIT);
-    pex->shaderManager->setDirty();
 
     glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
 
@@ -413,8 +412,7 @@ void QGL2PaintEngineExPrivate::setBrush(const QBrush& brush)
 
 void QGL2PaintEngineExPrivate::useSimpleShader()
 {
-    shaderManager->simpleProgram()->bind();
-    shaderManager->setDirty();
+    shaderManager->useSimpleProgram();
 
     if (matrixDirty)
         updateMatrix();
@@ -745,6 +743,10 @@ void QGL2PaintEngineEx::beginNativePainting()
     QGLContext *ctx = d->ctx;
     glUseProgram(0);
 
+    // Disable all the vertex attribute arrays:
+    for (int i = 0; i < QT_GL_VERTEX_ARRAY_TRACKED_COUNT; ++i)
+        glDisableVertexAttribArray(i);
+
 #ifndef QT_OPENGL_ES_2
     // be nice to people who mix OpenGL 1.x code with QPainter commands
     // by setting modelview and projection matrices to mirror the GL 1
@@ -1935,6 +1937,7 @@ void QGL2PaintEngineEx::ensureActive()
         glViewport(0, 0, d->width, d->height);
         d->needsSync = false;
         d->shaderManager->setDirty();
+        d->ctx->d_func()->syncGlState();
         setState(state());
     }
 }
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 466e851..5bb62f7 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -1484,6 +1484,8 @@ void QGLContextPrivate::init(QPaintDevice *dev, const QGLFormat &format)
     current_fbo = 0;
     default_fbo = 0;
     active_engine = 0;
+    for (int i = 0; i < QT_GL_VERTEX_ARRAY_TRACKED_COUNT; ++i)
+        vertexAttributeArraysEnabledState[i] = false;
 }
 
 QGLContext* QGLContext::currentCtx = 0;
@@ -1874,6 +1876,35 @@ void QGLContextPrivate::cleanup()
 {
 }
 
+#define ctx q_ptr
+void QGLContextPrivate::setVertexAttribArrayEnabled(int arrayIndex, bool enabled)
+{
+    Q_ASSERT(arrayIndex < QT_GL_VERTEX_ARRAY_TRACKED_COUNT);
+    Q_ASSERT(glEnableVertexAttribArray);
+
+    if (vertexAttributeArraysEnabledState[arrayIndex] && !enabled)
+        glDisableVertexAttribArray(arrayIndex);
+
+    if (!vertexAttributeArraysEnabledState[arrayIndex] && enabled)
+        glEnableVertexAttribArray(arrayIndex);
+
+    vertexAttributeArraysEnabledState[arrayIndex] = enabled;
+}
+
+void QGLContextPrivate::syncGlState()
+{
+    Q_ASSERT(glEnableVertexAttribArray);
+    for (int i = 0; i < QT_GL_VERTEX_ARRAY_TRACKED_COUNT; ++i) {
+        if (vertexAttributeArraysEnabledState[i])
+            glEnableVertexAttribArray(i);
+        else
+            glDisableVertexAttribArray(i);
+    }
+
+}
+#undef ctx
+
+
 /*!
     \overload
 
diff --git a/src/opengl/qgl.h b/src/opengl/qgl.h
index 2076c46..b6cd128 100644
--- a/src/opengl/qgl.h
+++ b/src/opengl/qgl.h
@@ -393,6 +393,7 @@ private:
     friend class QOpenGLPaintEnginePrivate;
     friend class QGL2PaintEngineEx;
     friend class QGL2PaintEngineExPrivate;
+    friend class QGLEngineShaderManager;
     friend class QGLWindowSurface;
     friend class QGLPixmapData;
     friend class QGLPixmapFilterBase;
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index 99c0f33..834ff96 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -257,6 +257,10 @@ private:
 
 class QGLTexture;
 
+// This probably needs to grow to GL_MAX_VERTEX_ATTRIBS, but 3 is ok for now as that's
+// all the GL2 engine uses:
+#define QT_GL_VERTEX_ARRAY_TRACKED_COUNT 3
+
 class QGLContextPrivate
 {
     Q_DECLARE_PUBLIC(QGLContext)
@@ -276,6 +280,9 @@ public:
 
     void cleanup();
 
+    void setVertexAttribArrayEnabled(int arrayIndex, bool enabled = true);
+    void syncGlState(); // Makes sure the GL context's state is what we think it is
+
 #if defined(Q_WS_WIN)
     HGLRC rc;
     HDC dc;
@@ -332,6 +339,8 @@ public:
     GLuint default_fbo;
     QPaintEngine *active_engine;
 
+    bool vertexAttributeArraysEnabledState[QT_GL_VERTEX_ARRAY_TRACKED_COUNT];
+
     static inline QGLContextGroup *contextGroup(const QGLContext *ctx) { return ctx->d_ptr->group; }
 
 #ifdef Q_WS_WIN