Started implementation of offscreen canvas FBO rendering API

Change-Id: I15b1799982d20d16c9c5e08eee7095cf087b49e1
Reviewed-by: Kim M. Kalland <kim.kalland@nokia.com>

3 files changed, 76 insertions, 9 deletions

diff --git a/src/quick/items/qquickcanvas.cpp b/src/quick/items/qquickcanvas.cpp
index ac7928f286..72300f9ce5 100644
--- a/src/quick/items/qquickcanvas.cpp
+++ b/src/quick/items/qquickcanvas.cpp
@@ -204,6 +204,30 @@ void QQuickCanvasPrivate::polishItems()
     updateFocusItemTransform();
 }
 
+/**
+ * This parameter enables that this canvas can be rendered without
+ * being shown on screen. This feature is very limited in what it supports.
+ *
+ * There needs to be another window actually showing that we can make current
+ * to get a surface to make current AND for this feature to be useful
+ * one needs to hook into beforeRender() and set the render tareget.
+ *
+ */
+void QQuickCanvasPrivate::setRenderWithoutShowing(bool render)
+{
+    if (render == renderWithoutShowing)
+        return;
+
+    Q_Q(QQuickCanvas);
+    renderWithoutShowing = render;
+
+    if (render)
+        windowManager->show(q);
+    else
+        windowManager->hide(q);
+}
+
+
 void forceUpdate(QQuickItem *item)
 {
     if (item->flags() & QQuickItem::ItemHasContents)
@@ -253,6 +277,7 @@ QQuickCanvasPrivate::QQuickCanvasPrivate()
     : rootItem(0)
     , activeFocusItem(0)
     , mouseGrabberItem(0)
+    , renderWithoutShowing(false)
     , dirtyItemList(0)
     , context(0)
     , renderer(0)
diff --git a/src/quick/items/qquickcanvas_p.h b/src/quick/items/qquickcanvas_p.h
index d5021d880a..45b87c67b7 100644
--- a/src/quick/items/qquickcanvas_p.h
+++ b/src/quick/items/qquickcanvas_p.h
@@ -93,7 +93,7 @@ class QTouchEvent;
 class QQuickCanvasRenderLoop;
 class QQuickCanvasIncubationController;
 
-class QQuickCanvasPrivate : public QWindowPrivate
+class Q_QUICK_EXPORT QQuickCanvasPrivate : public QWindowPrivate
 {
 public:
     Q_DECLARE_PUBLIC(QQuickCanvas)
@@ -152,6 +152,9 @@ public:
     void syncSceneGraph();
     void renderSceneGraph(const QSize &size);
 
+    bool renderWithoutShowing;
+    void setRenderWithoutShowing(bool enabled);
+
     QQuickItem::UpdatePaintNodeData updatePaintNodeData;
 
     QQuickItem *dirtyItemList;
diff --git a/src/quick/items/qquickwindowmanager.cpp b/src/quick/items/qquickwindowmanager.cpp
index b5dd2da746..d54be90385 100644
--- a/src/quick/items/qquickwindowmanager.cpp
+++ b/src/quick/items/qquickwindowmanager.cpp
@@ -208,6 +208,16 @@ public:
 
     void run();
 
+    QQuickCanvas *masterCanvas() {
+        QQuickCanvas *win = 0;
+        for (QHash<QQuickCanvas *, CanvasData *>::const_iterator it = m_rendered_windows.constBegin();
+            it != m_rendered_windows.constEnd() && !win; ++it) {
+            if (it.value()->isVisible)
+                win = it.key();
+        }
+        return win;
+    }
+
 public slots:
     void animationStarted();
     void animationStopped();
@@ -249,6 +259,7 @@ private:
         QSize viewportSize;
 
         uint sizeWasChanged : 1;
+        uint isVisible : 1;
     };
 
     QHash<QQuickCanvas *, CanvasData *> m_rendered_windows;
@@ -276,6 +287,7 @@ public:
 
     void canvasDestroyed(QQuickCanvas *canvas);
 
+    void initializeGL();
     void renderCanvas(QQuickCanvas *canvas);
     void paint(QQuickCanvas *canvas);
     QImage grab(QQuickCanvas *canvas);
@@ -329,7 +341,10 @@ QQuickWindowManager *QQuickWindowManager::instance()
 void QQuickRenderThreadSingleContextWindowManager::initialize()
 {
     Q_ASSERT(m_rendered_windows.size());
-    QQuickCanvas *win = m_rendered_windows.constBegin().key();
+
+    QQuickCanvas *win = masterCanvas();
+    if (!win)
+        return;
 
     gl = new QOpenGLContext();
     // Pick up the surface format from one of them
@@ -378,6 +393,7 @@ void QQuickRenderThreadSingleContextWindowManager::handleAddedWindow(QQuickCanva
     CanvasData *data = new CanvasData;
     data->sizeWasChanged = false;
     data->windowSize = canvas->size();
+    data->isVisible = canvas->visible();
     m_rendered_windows[canvas] = data;
 
     isExternalUpdatePending = true;
@@ -489,7 +505,7 @@ void QQuickRenderThreadSingleContextWindowManager::canvasVisibilityChanged()
         CanvasTracker &t = const_cast<CanvasTracker &>(m_tracked_windows.at(i));
         QQuickCanvas *win = t.canvas;
 
-        Q_ASSERT(win->visible() || t.toBeRemoved);
+        Q_ASSERT(win->visible() || QQuickCanvasPrivate::get(win)->renderWithoutShowing || t.toBeRemoved);
         bool canvasVisible = win->width() > 0 && win->height() > 0;
         anyoneShowing |= (canvasVisible && !t.toBeRemoved);
 
@@ -541,6 +557,9 @@ void QQuickRenderThreadSingleContextWindowManager::run()
     wake();
     unlock();
 
+    if (!gl)
+        return;
+
     while (!shouldExit) {
         lock();
 
@@ -591,7 +610,10 @@ void QQuickRenderThreadSingleContextWindowManager::run()
 
             Q_ASSERT(canvasData->windowSize.width() > 0 && canvasData->windowSize.height() > 0);
 
-            gl->makeCurrent(canvas);
+            if (!canvasData->isVisible)
+                gl->makeCurrent(masterCanvas());
+            else
+                gl->makeCurrent(canvas);
 
             if (canvasData->viewportSize != canvasData->windowSize) {
 #ifdef THREAD_DEBUG
@@ -660,7 +682,9 @@ void QQuickRenderThreadSingleContextWindowManager::run()
             printf("                RenderThread: --- wait for swap...\n");
 #endif
 
-            gl->swapBuffers(canvas);
+            if (canvasData->isVisible)
+                gl->swapBuffers(canvas);
+
             canvasPrivate->fireFrameSwapped();
 #ifdef THREAD_DEBUG
             printf("                RenderThread: --- swap complete...\n");
@@ -1141,15 +1165,30 @@ void QQuickTrivialWindowManager::renderCanvas(QQuickCanvas *canvas)
 
     CanvasData &data = const_cast<CanvasData &>(m_windows[canvas]);
 
+    QQuickCanvas *masterCanvas = 0;
+    if (!canvas->visible()) {
+        // Find a "proper surface" to bind...
+        for (QHash<QQuickCanvas *, CanvasData>::const_iterator it = m_windows.constBegin();
+             it != m_windows.constEnd() && !masterCanvas; ++it) {
+            if (it.key()->visible())
+                masterCanvas = it.key();
+        }
+    } else {
+        masterCanvas = canvas;
+    }
+
+    if (!masterCanvas)
+        return;
+
     if (!gl) {
         gl = new QOpenGLContext();
-        gl->setFormat(canvas->requestedFormat());
+        gl->setFormat(masterCanvas->requestedFormat());
         gl->create();
-        if (!gl->makeCurrent(canvas))
+        if (!gl->makeCurrent(masterCanvas))
             qWarning("QQuickCanvas: makeCurrent() failed...");
         sg->initialize(gl);
     } else {
-        gl->makeCurrent(canvas);
+        gl->makeCurrent(masterCanvas);
     }
 
     bool alsoSwap = data.updatePending;
@@ -1165,7 +1204,7 @@ void QQuickTrivialWindowManager::renderCanvas(QQuickCanvas *canvas)
         data.grabOnly = false;
     }
 
-    if (alsoSwap) {
+    if (alsoSwap && canvas->visible()) {
         gl->swapBuffers(canvas);
         cd->fireFrameSwapped();
     }