vo: use UpdateLater event for widgets instead of a signal

fix wang-bin#430 wang-bin#532
Less code and should be faster. Calling update() in User event should be
a solution too but more code is required.
WidgetRenderer::imageReady() is not removed because some people is using
it

src/QtAV/VideoRenderer.h

@@ -206,7 +206,7 @@ class Q_AV_EXPORT VideoRenderer : public AVOutput
     // TODO: parameter VideoFrame
     virtual void drawFrame() = 0; //You MUST reimplement this to display a frame. Other draw functions are not essential
     virtual void handlePaintEvent(); //has default. User don't have to implement it
-    virtual void updateUi(); // by default schedual an UpdateRequest event on ui thread
+    virtual void updateUi(); // by default post an UpdateRequest event for window and UpdateLater event for widget to ensure ui update
 
 private: //used by VideoOutput class
     // property change

src/output/video/OpenGLWidgetRenderer.cpp

@@ -44,12 +44,6 @@ OpenGLWidgetRenderer::OpenGLWidgetRenderer(QWidget *parent, Qt::WindowFlags f):
 {
     setAcceptDrops(true);
     setFocusPolicy(Qt::StrongFocus);
-    connect(this, SIGNAL(frameReady()), SLOT(update()));
-}
-
-void OpenGLWidgetRenderer::updateUi()
-{
-    Q_EMIT frameReady();
 }
 
 void OpenGLWidgetRenderer::initializeGL()

src/output/video/VideoRenderer.cpp

@@ -23,6 +23,7 @@
 #include "QtAV/private/VideoRenderer_p.h"
 #include "QtAV/Filter.h"
 #include <QtCore/QCoreApplication>
+#include <QtCore/QEvent>
 #include "QtAV/private/factory.h"
 #include "QtAV/private/mkid.h"
 #include "utils/Logger.h"
@@ -610,12 +611,26 @@ void VideoRenderer::onFrameSizeChanged(const QSize &size)
 
 void VideoRenderer::updateUi()
 {
-    QObject *obj = (QObject*)qwindow();
-    if (!obj)
-        obj = (QObject*)widget();
+    QObject *obj = (QObject*)widget();
     if (obj) {
-        QCoreApplication::instance()->postEvent(obj, new QEvent(QEvent::UpdateRequest));
+        // UpdateRequest only sync backing store but do not shedule repainting. UpdateLater does
+        // Copy from qwidget_p.h. QWidget::event() will convert UpdateLater to QUpdateLaterEvent and get it's region()
+        class QUpdateLaterEvent : public QEvent
+        {
+        public:
+            explicit QUpdateLaterEvent(const QRegion& paintRegion)
+                : QEvent(UpdateLater), m_region(paintRegion)
+            {}
+            ~QUpdateLaterEvent() {}
+            inline const QRegion &region() const { return m_region; }
+        protected:
+            QRegion m_region;
+        };
+        QCoreApplication::instance()->postEvent(obj, new QUpdateLaterEvent(QRegion(0, 0, rendererWidth(), rendererHeight())));
+    } else {
+        obj = (QObject*)qwindow();
+        if (obj)
+            QCoreApplication::instance()->postEvent(obj, new QEvent(QEvent::UpdateRequest));
     }
 }
-
 } //namespace QtAV

src/output/video/WidgetRenderer.cpp

@@ -60,7 +60,6 @@ WidgetRenderer::WidgetRenderer(QWidget *parent, Qt::WindowFlags f) :
     } else {
         qWarning("FilterContext not available!");
     }
-    connect(this, SIGNAL(imageReady()), SLOT(update()));
 }
 
 WidgetRenderer::WidgetRenderer(WidgetRendererPrivate &d, QWidget *parent, Qt::WindowFlags f)
@@ -76,18 +75,17 @@ WidgetRenderer::WidgetRenderer(WidgetRendererPrivate &d, QWidget *parent, Qt::Wi
     } else {
         qWarning("FilterContext not available!");
     }
-    connect(this, SIGNAL(frameReady()), SLOT(update()));
 }
 
 bool WidgetRenderer::receiveFrame(const VideoFrame &frame)
 {
     prepareFrame(frame);
-    //update();
+    updateUi();
     /*
      * workaround for the widget not updated if has parent. don't know why it works and why update() can't
      * Thanks to Vito Covito and Carlo Scarpato
+     * Now it's fixed by posting a QUpdateLaterEvent
      */
-    Q_EMIT frameReady();
     Q_EMIT imageReady();
     return true;
 }

widgets/QtAVWidgets/OpenGLWidgetRenderer.h

@@ -35,16 +35,12 @@ namespace QtAV {
 class OpenGLWidgetRendererPrivate;
 class Q_AVWIDGETS_EXPORT OpenGLWidgetRenderer : public QOpenGLWidget, public OpenGLRendererBase
 {
-    Q_OBJECT
     DPTR_DECLARE_PRIVATE(OpenGLWidgetRenderer)
 public:
     explicit OpenGLWidgetRenderer(QWidget* parent = 0, Qt::WindowFlags f = 0);
     virtual VideoRendererId id() const Q_DECL_OVERRIDE;
     virtual QWidget* widget() Q_DECL_OVERRIDE { return this; }
-Q_SIGNALS:
-    void frameReady();
 protected:
-    virtual void updateUi() Q_DECL_OVERRIDE;
     virtual void initializeGL() Q_DECL_OVERRIDE;
     virtual void paintGL() Q_DECL_OVERRIDE;
     virtual void resizeGL(int w, int h) Q_DECL_OVERRIDE;

widgets/QtAVWidgets/WidgetRenderer.h

@@ -42,8 +42,7 @@ class Q_AVWIDGETS_EXPORT WidgetRenderer : public QWidget, public QPainterRendere
     virtual VideoRendererId id() const;
     virtual QWidget* widget() { return this; }
 Q_SIGNALS:
-    void frameReady();
-    QTAVWIDGETS_DEPRECATED void imageReady(); // use frameReady() instead
+    QTAVWIDGETS_DEPRECATED void imageReady(); // add frameReady() in the future?
 protected:
     virtual bool receiveFrame(const VideoFrame& frame);
     virtual bool needUpdateBackground() const;