Renderloop for Windows

The normal GUI thread render loop has several problems on windows.
It does not do vsync animations and on some hardware, where the
vsync delta is higher than the time it takes to fire a 16ms timer,
the eventloop will always contain at least one event and we never
return to processing non-client area events, like resize.

Also, threaded OpenGL seems rather unstable, so the threaded renderer
is not a stable option.

So we introduce a windows based renderloop. It is fully cross platform
but written to make the most out of the limitations which exist.

The overall goal is:
  - vsync animations when allowed by the system. We get this by
    using an animation driver and advancing in sync with rendering
  - Keep system load low and allow for NC processing. The maybeUpdate
    function will start a short timer which will let the renderloop
    idle for few ms, allowing the eventloop to pick up system events.
    (this is similar to what the threaded renderer also does, btw)

Change-Id: Ic192fd0ed7d5ecdaa2c887c08cbeb42c5de6b8a8
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>

1 files changed, 114 insertions, 0 deletions

diff --git a/src/quick/scenegraph/qsgwindowsrenderloop_p.h b/src/quick/scenegraph/qsgwindowsrenderloop_p.h
new file mode 100644
index 0000000000..dc3a409cd5
--- /dev/null
+++ b/src/quick/scenegraph/qsgwindowsrenderloop_p.h
@@ -0,0 +1,114 @@
+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the QtQml module of the Qt Toolkit.
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+** GNU Lesser General Public License Usage
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+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
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+** rights.  These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
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+** $QT_END_LICENSE$
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+****************************************************************************/
+
+#ifndef QSGWINDOWSRENDERLOOP_P_H
+#define QSGWINDOWSRENDERLOOP_P_H
+
+#include <QtCore/QObject>
+#include <QtCore/QElapsedTimer>
+
+#include <QtGui/QOpenGLContext>
+
+#include "qsgrenderloop_p.h"
+
+QT_BEGIN_NAMESPACE
+
+class QSGWindowsRenderLoop : public QObject, public QSGRenderLoop
+{
+    Q_OBJECT
+public:
+    explicit QSGWindowsRenderLoop();
+
+    void show(QQuickWindow *window);
+    void hide(QQuickWindow *window);
+
+    void windowDestroyed(QQuickWindow *window);
+
+    void exposureChanged(QQuickWindow *window);
+    QImage grab(QQuickWindow *window);
+
+    void update(QQuickWindow *window);
+    void maybeUpdate(QQuickWindow *window);
+
+    QAnimationDriver *animationDriver() const { return m_animationDriver; }
+
+    QSGContext *sceneGraphContext() const { return m_sg; }
+
+    void releaseResources(QQuickWindow *) { }
+
+    void render();
+    void renderWindow(QQuickWindow *window);
+
+    void resize(QQuickWindow *, const QSize &) { }
+
+    bool event(QEvent *event);
+
+public slots:
+    void started();
+    void stopped();
+
+private:
+    struct WindowData {
+        QQuickWindow *window;
+        bool pendingUpdate;
+    };
+
+    void handleObscurity();
+    void maybePostUpdateTimer();
+    bool anyoneShowing() const;
+    WindowData *windowData(QQuickWindow *window);
+
+    QList<WindowData> m_windows;
+
+    QOpenGLContext *m_gl;
+    QSGContext *m_sg;
+
+    QAnimationDriver *m_animationDriver;
+
+    int m_updateTimer;
+    int m_animationTimer;
+
+    int m_vsyncDelta;
+};
+
+QT_END_NAMESPACE
+
+#endif // QSGWINDOWSRENDERLOOP_P_H