Make canvas cleanup work propertly...

Depending on which mode we are in, we need to run cleanup
on the right thread and in the right way.

Image canvas doesn't contain any GL resources and can be nuked
right away. The actual QSGTexture is managed by the node, so we
don't need to worry about it.

For FBO it is a bit more complicated.
 - Threaded: We create a cleanup handler that runs makeCurrent
   deleteTexture and doneCurrent and then release the surface
   on the GUI thread.
 - Immediate: Same as threaded, just right away
 - Cooperative: Schedule the texture to be deleted on the
   next sync. The Context doesn't have its own GL context
   in this case, so don't worry about it.

Change-Id: I2d0ae7acfa05561faa52f3cacd767eb18cabaf02
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

3 files changed, 48 insertions, 2 deletions

diff --git a/src/quick/items/context2d/qquickcontext2d.cpp b/src/quick/items/context2d/qquickcontext2d.cpp
index a7d5f7d65f..8858958dbc 100644
--- a/src/quick/items/context2d/qquickcontext2d.cpp
+++ b/src/quick/items/context2d/qquickcontext2d.cpp
@@ -70,6 +70,8 @@
 #include <private/qv4objectproto_p.h>
 #include <private/qv4scopedvalue_p.h>
 
+#include <QtCore/QRunnable>
+
 #if defined(Q_OS_QNX) || defined(Q_OS_ANDROID)
 #include <ctype.h>
 #endif
@@ -4061,6 +4063,27 @@ bool QQuickContext2D::isPointInPath(qreal x, qreal y) const
     return contains;
 }
 
+class QQuickContext2DThreadCleanup : public QObject
+{
+public:
+    QQuickContext2DThreadCleanup(QOpenGLContext *gl, QQuickContext2DTexture *t, QOffscreenSurface *s)
+        : context(gl), texture(t), surface(s)
+    { }
+
+    ~QQuickContext2DThreadCleanup()
+    {
+        context->makeCurrent(surface);
+        delete texture;
+        context->doneCurrent();
+        delete context;
+        surface->deleteLater();
+    }
+
+    QOpenGLContext *context;
+    QQuickContext2DTexture *texture;
+    QOffscreenSurface *surface;
+};
+
 QQuickContext2D::QQuickContext2D(QObject *parent)
     : QQuickCanvasContext(parent)
     , m_buffer(new QQuickContext2DCommandBuffer)
@@ -4075,7 +4098,28 @@ QQuickContext2D::QQuickContext2D(QObject *parent)
 QQuickContext2D::~QQuickContext2D()
 {
     delete m_buffer;
-    m_texture->deleteLater();
+
+    if (m_renderTarget == QQuickCanvasItem::FramebufferObject) {
+        if (m_renderStrategy == QQuickCanvasItem::Immediate && m_glContext) {
+            Q_ASSERT(QThread::currentThread() == m_glContext->thread());
+            m_glContext->makeCurrent(m_surface.data());
+            delete m_texture;
+            m_glContext->doneCurrent();
+            delete m_glContext;
+        } else if (m_texture->isOnCustomThread()) {
+            Q_ASSERT(m_glContext);
+            QQuickContext2DThreadCleanup *cleaner = new QQuickContext2DThreadCleanup(m_glContext, m_texture, m_surface.take());
+            cleaner->moveToThread(m_texture->thread());
+            cleaner->deleteLater();
+        } else {
+            m_texture->deleteLater();
+        }
+    } else {
+        // Image based does not have GL resources, but must still be deleted
+        // on its designated thread after it has completed whatever it might
+        // currently be doing.
+        m_texture->deleteLater();
+    }
 }
 
 QV4::ReturnedValue QQuickContext2D::v4value() const
diff --git a/src/quick/items/context2d/qquickcontext2dtexture.cpp b/src/quick/items/context2d/qquickcontext2dtexture.cpp
index ca66bd7f5a..4007713152 100644
--- a/src/quick/items/context2d/qquickcontext2dtexture.cpp
+++ b/src/quick/items/context2d/qquickcontext2dtexture.cpp
@@ -414,7 +414,8 @@ QQuickContext2DFBOTexture::~QQuickContext2DFBOTexture()
     delete m_multisampledFbo;
     delete m_paint_device;
 
-    glDeleteTextures(2, m_displayTextures);
+    if (QOpenGLContext::currentContext())
+        glDeleteTextures(2, m_displayTextures);
 }
 
 QSGTexture *QQuickContext2DFBOTexture::textureForNextFrame(QSGTexture *lastTexture)
diff --git a/src/quick/items/context2d/qquickcontext2dtexture_p.h b/src/quick/items/context2d/qquickcontext2dtexture_p.h
index cf0e8e3fa9..186863c1aa 100644
--- a/src/quick/items/context2d/qquickcontext2dtexture_p.h
+++ b/src/quick/items/context2d/qquickcontext2dtexture_p.h
@@ -107,6 +107,7 @@ public:
     bool setDirtyRect(const QRect &dirtyRect);
     bool canvasDestroyed();
     void setOnCustomThread(bool is) { m_onCustomThread = is; }
+    bool isOnCustomThread() const { return m_onCustomThread; }
 
     // Called during sync() on the scene graph thread while GUI is blocked.
     virtual QSGTexture *textureForNextFrame(QSGTexture *lastFrame) = 0;