Fixed bugs in GL2 paint engine when several engines are active.

Make sure makeCurrent() on a window surface unbinds any active FBO, and
simplify ensureActive() code in GL2 paint engine a bit. We don't need
the last_engine pointer as ensureActive() will take care of ensuring the
correct engine is active anway.

4 files changed, 41 insertions, 33 deletions

diff --git a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
index f174306..a7c7426 100644
--- a/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
+++ b/src/opengl/gl2paintengineex/qpaintengineex_opengl2.cpp
@@ -175,8 +175,6 @@ public:
     void updateDepthClip();
     void systemStateChanged();
     uint use_system_clip : 1;
-
-    QPaintEngine *last_engine;
 };
 
 
@@ -830,10 +828,11 @@ void QGL2PaintEngineEx::stroke(const QVectorPath &path, const QPen &pen)
 {
     Q_D(QGL2PaintEngineEx);
 
-    ensureActive();
     if (pen.style() == Qt::NoPen)
         return;
 
+    ensureActive();
+
     if ( (pen.isCosmetic() && (pen.style() == Qt::SolidLine)) && (pen.widthF() < 2.5f) )
     {
         // We only handle solid, cosmetic pens with a width of 1 pixel
@@ -1051,10 +1050,19 @@ bool QGL2PaintEngineEx::begin(QPaintDevice *pdev)
     Q_D(QGL2PaintEngineEx);
 
 //     qDebug("QGL2PaintEngineEx::begin()");
-
     d->drawable.setDevice(pdev);
-    d->drawable.makeCurrent();
     d->ctx = d->drawable.context();
+
+    if (d->ctx->d_ptr->active_engine) {
+        QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(d->ctx->d_ptr->active_engine);
+        QGL2PaintEngineExPrivate *p = static_cast<QGL2PaintEngineExPrivate *>(engine->d_ptr);
+        p->transferMode(BrushDrawingMode);
+        p->drawable.doneCurrent();
+    }
+
+    d->ctx->d_ptr->active_engine = this;
+
+    d->drawable.makeCurrent();
     QSize sz = d->drawable.size();
     d->width = sz.width();
     d->height = sz.height();
@@ -1064,14 +1072,6 @@ bool QGL2PaintEngineEx::begin(QPaintDevice *pdev)
     qt_resolve_version_2_0_functions(d->ctx);
 #endif
 
-    d->last_engine = d->ctx->d_ptr->active_engine;
-    d->ctx->d_ptr->active_engine = this;
-
-    if (d->last_engine) {
-        QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(d->last_engine);
-        static_cast<QGL2PaintEngineExPrivate *>(engine->d_ptr)->transferMode(BrushDrawingMode);
-    }
-
     if (!d->shaderManager)
         d->shaderManager = new QGLEngineShaderManager(d->ctx);
 
@@ -1115,8 +1115,8 @@ bool QGL2PaintEngineEx::end()
     Q_D(QGL2PaintEngineEx);
     QGLContext *ctx = d->ctx;
     if (ctx->d_ptr->active_engine != this) {
-        QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(d->last_engine);
-        if (engine) {
+        QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(ctx->d_ptr->active_engine);
+        if (engine && engine->isActive()) {
             QGL2PaintEngineExPrivate *p = static_cast<QGL2PaintEngineExPrivate *>(engine->d_ptr);
             p->transferMode(BrushDrawingMode);
             p->drawable.doneCurrent();
@@ -1128,19 +1128,7 @@ bool QGL2PaintEngineEx::end()
     d->transferMode(BrushDrawingMode);
     d->drawable.swapBuffers();
     d->drawable.doneCurrent();
-    d->ctx->d_ptr->active_engine = d->last_engine;
-
-    if (d->last_engine) {
-        QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(d->last_engine);
-        QGL2PaintEngineExPrivate *p = static_cast<QGL2PaintEngineExPrivate *>(engine->d_ptr);
-
-        glDisable(GL_DEPTH_TEST);
-        glDisable(GL_SCISSOR_TEST);
-
-        glViewport(0, 0, p->width, p->height);
-        engine->setState(engine->state());
-        p->updateDepthClip();
-    }
+    d->ctx->d_ptr->active_engine = 0;
 
     return false;
 }
@@ -1152,7 +1140,7 @@ void QGL2PaintEngineEx::ensureActive()
 
     if (isActive() && ctx->d_ptr->active_engine != this) {
         QGL2PaintEngineEx *engine = static_cast<QGL2PaintEngineEx *>(ctx->d_ptr->active_engine);
-        if (engine) {
+        if (engine && engine->isActive()) {
             QGL2PaintEngineExPrivate *p = static_cast<QGL2PaintEngineExPrivate *>(engine->d_ptr);
             p->transferMode(BrushDrawingMode);
             p->drawable.doneCurrent();
diff --git a/src/opengl/qgl.cpp b/src/opengl/qgl.cpp
index 0a2a196..62a592a 100644
--- a/src/opengl/qgl.cpp
+++ b/src/opengl/qgl.cpp
@@ -4391,6 +4391,15 @@ void QGLDrawable::swapBuffers()
 
 void QGLDrawable::makeCurrent()
 {
+    previous_fbo = 0;
+    if (!pixmapData && !fbo) {
+        QGLContext *ctx = context();
+        previous_fbo = ctx->d_ptr->current_fbo;
+        ctx->d_ptr->current_fbo = 0;
+        if (previous_fbo)
+            glBindFramebuffer(GL_FRAMEBUFFER_EXT, 0);
+    }
+
     if (widget)
         widget->makeCurrent();
 #if !defined(QT_OPENGL_ES_1) && !defined(QT_OPENGL_ES_1_CL)
@@ -4428,6 +4437,12 @@ void QGLDrawable::doneCurrent()
     }
 #endif
 
+    if (previous_fbo) {
+        QGLContext *ctx = context();
+        ctx->d_ptr->current_fbo = previous_fbo;
+        glBindFramebuffer(GL_FRAMEBUFFER_EXT, previous_fbo);
+    }
+
     if (fbo && !wasBound)
         fbo->release();
 }
diff --git a/src/opengl/qgl_p.h b/src/opengl/qgl_p.h
index b421eee..9657416 100644
--- a/src/opengl/qgl_p.h
+++ b/src/opengl/qgl_p.h
@@ -333,6 +333,7 @@ private:
 #if !defined(QT_OPENGL_ES_1) && !defined(QT_OPENGL_ES_1_CL)
     QGLPixmapData *pixmapData;
 #endif
+    int previous_fbo;
 };
 
 // GL extension definitions
diff --git a/src/opengl/qglframebufferobject.cpp b/src/opengl/qglframebufferobject.cpp
index 338ce1f..3e7ca0a 100644
--- a/src/opengl/qglframebufferobject.cpp
+++ b/src/opengl/qglframebufferobject.cpp
@@ -804,8 +804,10 @@ bool QGLFramebufferObject::bind()
     const QGLContext *context = QGLContext::currentContext();
     if (d->valid && context) {
         // Save the previous setting to automatically restore in release().
-        d->previous_fbo = context->d_ptr->current_fbo;
-        context->d_ptr->current_fbo = d->fbo;
+        if (context->d_ptr->current_fbo != d->fbo) {
+            d->previous_fbo = context->d_ptr->current_fbo;
+            context->d_ptr->current_fbo = d->fbo;
+        }
     }
     return d->valid;
 }
@@ -834,8 +836,10 @@ bool QGLFramebufferObject::release()
     const QGLContext *context = QGLContext::currentContext();
     if (context) {
         // Restore the previous setting for stacked framebuffer objects.
-        context->d_ptr->current_fbo = d->previous_fbo;
-        glBindFramebuffer(GL_FRAMEBUFFER_EXT, d->previous_fbo);
+        if (d->previous_fbo != context->d_ptr->current_fbo) {
+            context->d_ptr->current_fbo = d->previous_fbo;
+            glBindFramebuffer(GL_FRAMEBUFFER_EXT, d->previous_fbo);
+        }
         d->previous_fbo = 0;
     }