More QQuickCanvas cleanup handling.

Avoid calling into QQuickContext2D from QQuickContext2DTexture
after QQuickContext2D has been deleted. We acheive this by

1. Giving the texture a direct pointer to the gl context and
   and surface, so that it doesn't need to go through m_context
   to get to them (which may have been deleted).

2. Protect access to QQuickContext2DTexture::m_context with
   a mutex and make sure it is set to 0 in a safe manner
   when the QQuickContext2D object is deleted.

Change-Id: Ie0a30f9fc46f844224838a7cdf2f28a62e8ce322
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

4 files changed, 47 insertions, 28 deletions

diff --git a/src/quick/items/context2d/qquickcontext2d.cpp b/src/quick/items/context2d/qquickcontext2d.cpp
index 8858958dbc..7964f650d6 100644
--- a/src/quick/items/context2d/qquickcontext2d.cpp
+++ b/src/quick/items/context2d/qquickcontext2d.cpp
@@ -4084,6 +4084,8 @@ public:
     QOffscreenSurface *surface;
 };
 
+QMutex QQuickContext2D::mutex;
+
 QQuickContext2D::QQuickContext2D(QObject *parent)
     : QQuickCanvasContext(parent)
     , m_buffer(new QQuickContext2DCommandBuffer)
@@ -4097,6 +4099,8 @@ QQuickContext2D::QQuickContext2D(QObject *parent)
 
 QQuickContext2D::~QQuickContext2D()
 {
+    mutex.lock();
+    m_texture->setItem(0);
     delete m_buffer;
 
     if (m_renderTarget == QQuickCanvasItem::FramebufferObject) {
@@ -4120,6 +4124,7 @@ QQuickContext2D::~QQuickContext2D()
         // currently be doing.
         m_texture->deleteLater();
     }
+    mutex.unlock();
 }
 
 QV4::ReturnedValue QQuickContext2D::v4value() const
@@ -4190,6 +4195,7 @@ void QQuickContext2D::init(QQuickCanvasItem *canvasItem, const QVariantMap &args
          m_glContext->setShareContext(cc);
          if (renderThread != QThread::currentThread())
              m_glContext->moveToThread(renderThread);
+         m_texture->initializeOpenGL(m_glContext, m_surface.data());
     }
 
     connect(m_texture, SIGNAL(textureChanged()), SIGNAL(textureChanged()));
@@ -4379,10 +4385,4 @@ void QQuickContext2D::setV8Engine(QV8Engine *engine)
     }
 }
 
-QQuickContext2DCommandBuffer* QQuickContext2D::nextBuffer()
-{
-    QMutexLocker lock(&m_mutex);
-    return m_bufferQueue.isEmpty() ? 0 : m_bufferQueue.dequeue();
-}
-
 QT_END_NAMESPACE
diff --git a/src/quick/items/context2d/qquickcontext2d_p.h b/src/quick/items/context2d/qquickcontext2d_p.h
index bd1a83ce08..c679bc33cb 100644
--- a/src/quick/items/context2d/qquickcontext2d_p.h
+++ b/src/quick/items/context2d/qquickcontext2d_p.h
@@ -185,7 +185,6 @@ public:
 
     QQuickCanvasItem* canvas() const { return m_canvas; }
     QQuickContext2DCommandBuffer* buffer() const { return m_buffer; }
-    QQuickContext2DCommandBuffer* nextBuffer();
 
     bool bufferValid() const { return m_buffer != 0; }
     void popState();
@@ -255,7 +254,7 @@ public:
     QImage m_grabbedImage;
     bool m_grabbed:1;
 
-    QMutex m_mutex;
+    static QMutex mutex;
 };
 
 
diff --git a/src/quick/items/context2d/qquickcontext2dtexture.cpp b/src/quick/items/context2d/qquickcontext2dtexture.cpp
index 4007713152..c8bea6f97e 100644
--- a/src/quick/items/context2d/qquickcontext2dtexture.cpp
+++ b/src/quick/items/context2d/qquickcontext2dtexture.cpp
@@ -90,6 +90,8 @@ struct GLAcquireContext {
 
 QQuickContext2DTexture::QQuickContext2DTexture()
     : m_context(0)
+    , m_gl(0)
+    , m_surface(0)
     , m_item(0)
     , m_canvasWindowChanged(false)
     , m_dirtyTexture(false)
@@ -146,8 +148,12 @@ void QQuickContext2DTexture::setAntialiasing(bool antialiasing)
 void QQuickContext2DTexture::setItem(QQuickCanvasItem* item)
 {
     m_item = item;
-    m_context = (QQuickContext2D*)item->rawContext(); // FIXME
-    m_state = m_context->state;
+    if (m_item) {
+        m_context = (QQuickContext2D*) item->rawContext(); // FIXME
+        m_state = m_context->state;
+    } else {
+        m_context = 0;
+    }
 }
 
 bool QQuickContext2DTexture::setCanvasWindow(const QRect& r)
@@ -239,12 +245,15 @@ bool QQuickContext2DTexture::canvasDestroyed()
 
 void QQuickContext2DTexture::paint(QQuickContext2DCommandBuffer *ccb)
 {
+    QQuickContext2D::mutex.lock();
     if (canvasDestroyed()) {
         delete ccb;
+        QQuickContext2D::mutex.unlock();
         return;
     }
+    QQuickContext2D::mutex.unlock();
 
-    GLAcquireContext currentContext(m_context->glContext(), m_context->surface());
+    GLAcquireContext currentContext(m_gl, m_surface);
 
     if (!m_tiledCanvas) {
         paintWithoutTiles(ccb);
@@ -434,7 +443,7 @@ QSGTexture *QQuickContext2DFBOTexture::textureForNextFrame(QSGTexture *lastTextu
         }
 
         if (m_dirtyTexture) {
-            if (!m_context->glContext()) {
+            if (!m_gl) {
                 // on a rendering thread, use the fbo directly...
                 texture->setTextureId(m_fbo->texture());
             } else {
@@ -492,18 +501,18 @@ bool QQuickContext2DFBOTexture::doMultisampling() const
 void QQuickContext2DFBOTexture::grabImage(const QRectF& rf)
 {
     Q_ASSERT(rf.isValid());
-    if (!m_fbo) {
-        m_context->setGrabbedImage(QImage());
-        return;
-    }
-
-    QImage grabbed;
-    {
-        GLAcquireContext ctx(m_context->glContext(), m_context->surface());
-        grabbed = m_fbo->toImage().mirrored().copy(rf.toRect());
+    QQuickContext2D::mutex.lock();
+    if (m_context) {
+        if (!m_fbo) {
+            m_context->setGrabbedImage(QImage());
+        } else {
+            QImage grabbed;
+            GLAcquireContext ctx(m_gl, m_surface);
+            grabbed = m_fbo->toImage().mirrored().copy(rf.toRect());
+            m_context->setGrabbedImage(grabbed);
+        }
     }
-
-    m_context->setGrabbedImage(grabbed);
+    QQuickContext2D::mutex.unlock();
 }
 
 void QQuickContext2DFBOTexture::compositeTile(QQuickContext2DTile* tile)
@@ -586,7 +595,7 @@ void QQuickContext2DFBOTexture::endPainting()
     if (m_multisampledFbo)
         QOpenGLFramebufferObject::blitFramebuffer(m_fbo, m_multisampledFbo);
 
-    if (m_context->glContext()) {
+    if (m_gl) {
         /* When rendering happens on the render thread, the fbo's texture is
          * used directly for display. If we are on the GUI thread or a
          * dedicated Canvas render thread, we need to decouple the FBO from
@@ -641,9 +650,12 @@ QQuickContext2DTile* QQuickContext2DImageTexture::createTile() const
 void QQuickContext2DImageTexture::grabImage(const QRectF& rf)
 {
     Q_ASSERT(rf.isValid());
-    Q_ASSERT(m_context);
-    QImage grabbed = m_displayImage.copy(rf.toRect());
-    m_context->setGrabbedImage(grabbed);
+    QQuickContext2D::mutex.lock();
+    if (m_context) {
+        QImage grabbed = m_displayImage.copy(rf.toRect());
+        m_context->setGrabbedImage(grabbed);
+    }
+    QQuickContext2D::mutex.unlock();
 }
 
 QSGTexture *QQuickContext2DImageTexture::textureForNextFrame(QSGTexture *last)
diff --git a/src/quick/items/context2d/qquickcontext2dtexture_p.h b/src/quick/items/context2d/qquickcontext2dtexture_p.h
index 186863c1aa..e41a4809e4 100644
--- a/src/quick/items/context2d/qquickcontext2dtexture_p.h
+++ b/src/quick/items/context2d/qquickcontext2dtexture_p.h
@@ -113,6 +113,11 @@ public:
     virtual QSGTexture *textureForNextFrame(QSGTexture *lastFrame) = 0;
     bool event(QEvent *e);
 
+    void initializeOpenGL(QOpenGLContext *gl, QOffscreenSurface *s) {
+        m_gl = gl;
+        m_surface = s;
+    }
+
 Q_SIGNALS:
     void textureChanged();
 
@@ -135,7 +140,10 @@ protected:
     QRect createTiles(const QRect& window);
 
     QList<QQuickContext2DTile*> m_tiles;
-    QQuickContext2D* m_context;
+    QQuickContext2D *m_context;
+
+    QOpenGLContext *m_gl;
+    QSurface *m_surface;
 
     QQuickContext2D::State m_state;