Added QScreen::refreshRate() to get the vertical refresh rate.

To give applications that want it the option to use a fixed timestep for
animations, and to avoid having values of 60 hard-coded (we have a
couple of those in qtdeclarative/src/quick already), we need to know the
refresh rates of the screens we are rendering to.

Change-Id: Ife49162e830440ad7eab563a27e8aebbbafc5fc5
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>

10 files changed, 66 insertions, 0 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 631592aace..62303eeea2 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -1090,6 +1090,10 @@ void QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePriv
         QGuiApplicationPrivate::reportLogicalDotsPerInchChange(
                 static_cast<QWindowSystemInterfacePrivate::ScreenLogicalDotsPerInchEvent *>(e));
         break;
+    case QWindowSystemInterfacePrivate::ScreenRefreshRate:
+        QGuiApplicationPrivate::reportRefreshRateChange(
+                static_cast<QWindowSystemInterfacePrivate::ScreenRefreshRateEvent *>(e));
+        break;
     case QWindowSystemInterfacePrivate::ThemeChange:
         QGuiApplicationPrivate::processThemeChanged(
                     static_cast<QWindowSystemInterfacePrivate::ThemeChangeEvent *>(e));
@@ -1750,6 +1754,21 @@ void QGuiApplicationPrivate::reportLogicalDotsPerInchChange(QWindowSystemInterfa
     emit s->logicalDotsPerInchChanged(s->logicalDotsPerInch());
 }
 
+void QGuiApplicationPrivate::reportRefreshRateChange(QWindowSystemInterfacePrivate::ScreenRefreshRateEvent *e)
+{
+    // This operation only makes sense after the QGuiApplication constructor runs
+    if (QCoreApplication::startingUp())
+        return;
+
+    if (!e->screen)
+        return;
+
+    QScreen *s = e->screen.data();
+    s->d_func()->refreshRate = e->rate;
+
+    emit s->refreshRateChanged(s->refreshRate());
+}
+
 void QGuiApplicationPrivate::processExposeEvent(QWindowSystemInterfacePrivate::ExposeEvent *e)
 {
     if (!e->exposed)
diff --git a/src/gui/kernel/qguiapplication_p.h b/src/gui/kernel/qguiapplication_p.h
index cb3587ba63..860c41d648 100644
--- a/src/gui/kernel/qguiapplication_p.h
+++ b/src/gui/kernel/qguiapplication_p.h
@@ -117,6 +117,7 @@ public:
     static void reportGeometryChange(QWindowSystemInterfacePrivate::ScreenGeometryEvent *e);
     static void reportAvailableGeometryChange(QWindowSystemInterfacePrivate::ScreenAvailableGeometryEvent *e);
     static void reportLogicalDotsPerInchChange(QWindowSystemInterfacePrivate::ScreenLogicalDotsPerInchEvent *e);
+    static void reportRefreshRateChange(QWindowSystemInterfacePrivate::ScreenRefreshRateEvent *e);
     static void processThemeChanged(QWindowSystemInterfacePrivate::ThemeChangeEvent *tce);
 
     static void processExposeEvent(QWindowSystemInterfacePrivate::ExposeEvent *e);
diff --git a/src/gui/kernel/qplatformscreen.h b/src/gui/kernel/qplatformscreen.h
index 075dfb114b..1743024d91 100644
--- a/src/gui/kernel/qplatformscreen.h
+++ b/src/gui/kernel/qplatformscreen.h
@@ -101,6 +101,8 @@ public:
     virtual QSizeF physicalSize() const;
     virtual QDpi logicalDpi() const;
 
+    virtual qreal refreshRate() const;
+
     virtual Qt::ScreenOrientation orientation() const;
 
     virtual QWindow *topLevelAt(const QPoint &point) const;
diff --git a/src/gui/kernel/qplatformscreen_qpa.cpp b/src/gui/kernel/qplatformscreen_qpa.cpp
index 6c2f98beb4..1fd96a80a5 100644
--- a/src/gui/kernel/qplatformscreen_qpa.cpp
+++ b/src/gui/kernel/qplatformscreen_qpa.cpp
@@ -161,6 +161,17 @@ QDpi QPlatformScreen::logicalDpi() const
 }
 
 /*!
+    Reimplement this function in subclass to return the vertical refresh rate
+    of the screen, in Hz.
+
+    The default returns 60, a sensible default for modern displays.
+*/
+qreal QPlatformScreen::refreshRate() const
+{
+    return 60;
+}
+
+/*!
     Reimplement this function in subclass to return the current orientation
     of the screen, for example based on accelerometer data to determine
     the device orientation.
diff --git a/src/gui/kernel/qscreen.cpp b/src/gui/kernel/qscreen.cpp
index 716caacb40..2e0df43e66 100644
--- a/src/gui/kernel/qscreen.cpp
+++ b/src/gui/kernel/qscreen.cpp
@@ -364,6 +364,16 @@ Qt::ScreenOrientation QScreen::orientation() const
 }
 
 /*!
+  \property QScreen::refreshRate
+  \brief the approximate vertical refresh rate of the screen in Hz
+*/
+qreal QScreen::refreshRate() const
+{
+    Q_D(const QScreen);
+    return d->refreshRate;
+}
+
+/*!
     \property QScreen::primaryOrientation
     \brief the primary screen orientation
 
diff --git a/src/gui/kernel/qscreen.h b/src/gui/kernel/qscreen.h
index f69e04a595..17f3cd3d43 100644
--- a/src/gui/kernel/qscreen.h
+++ b/src/gui/kernel/qscreen.h
@@ -83,6 +83,7 @@ class Q_GUI_EXPORT QScreen : public QObject
     Q_PROPERTY(QRect availableGeometry READ availableGeometry NOTIFY availableGeometryChanged)
     Q_PROPERTY(Qt::ScreenOrientation primaryOrientation READ orientation NOTIFY primaryOrientationChanged)
     Q_PROPERTY(Qt::ScreenOrientation orientation READ orientation NOTIFY orientationChanged)
+    Q_PROPERTY(qreal refreshRate READ refreshRate NOTIFY refreshRateChanged)
 
 public:
     QPlatformScreen *handle() const;
@@ -127,6 +128,8 @@ public:
 
     QPixmap grabWindow(WId window, int x, int y, int w, int h);
 
+    qreal refreshRate() const;
+
 Q_SIGNALS:
     void sizeChanged(const QSize &size);
     void geometryChanged(const QRect &geometry);
@@ -140,6 +143,7 @@ Q_SIGNALS:
     void availableGeometryChanged(const QRect &rect);
     void primaryOrientationChanged(Qt::ScreenOrientation orientation);
     void orientationChanged(Qt::ScreenOrientation orientation);
+    void refreshRateChanged(qreal refreshRate);
 
 private:
     explicit QScreen(QPlatformScreen *screen);
diff --git a/src/gui/kernel/qscreen_p.h b/src/gui/kernel/qscreen_p.h
index 0167384b01..b0e1b8671a 100644
--- a/src/gui/kernel/qscreen_p.h
+++ b/src/gui/kernel/qscreen_p.h
@@ -63,6 +63,7 @@ public:
         geometry = screen->geometry();
         availableGeometry = screen->availableGeometry();
         logicalDpi = screen->logicalDpi();
+        refreshRate = screen->refreshRate();
 
         updatePrimaryOrientation();
     }
@@ -74,6 +75,7 @@ public:
     QRect geometry;
     QRect availableGeometry;
     QDpi logicalDpi;
+    qreal refreshRate;
 
     QPlatformScreen *platformScreen;
 };
diff --git a/src/gui/kernel/qwindowsysteminterface_qpa.cpp b/src/gui/kernel/qwindowsysteminterface_qpa.cpp
index 83cf8c338c..c3136b0b0a 100644
--- a/src/gui/kernel/qwindowsysteminterface_qpa.cpp
+++ b/src/gui/kernel/qwindowsysteminterface_qpa.cpp
@@ -434,6 +434,13 @@ void QWindowSystemInterface::handleScreenLogicalDotsPerInchChange(QScreen *scree
     QWindowSystemInterfacePrivate::queueWindowSystemEvent(e);
 }
 
+void QWindowSystemInterface::handleScreenRefreshRateChange(QScreen *screen, qreal newRefreshRate)
+{
+    QWindowSystemInterfacePrivate::ScreenRefreshRateEvent *e =
+            new QWindowSystemInterfacePrivate::ScreenRefreshRateEvent(screen, newRefreshRate);
+    QWindowSystemInterfacePrivate::queueWindowSystemEvent(e);
+}
+
 void QWindowSystemInterface::handleThemeChange(QWindow *tlw)
 {
     QWindowSystemInterfacePrivate::ThemeChangeEvent *e = new QWindowSystemInterfacePrivate::ThemeChangeEvent(tlw);
diff --git a/src/gui/kernel/qwindowsysteminterface_qpa.h b/src/gui/kernel/qwindowsysteminterface_qpa.h
index 1fbf430bf9..7e0ebf0efc 100644
--- a/src/gui/kernel/qwindowsysteminterface_qpa.h
+++ b/src/gui/kernel/qwindowsysteminterface_qpa.h
@@ -144,6 +144,7 @@ public:
     static void handleScreenGeometryChange(QScreen *screen, const QRect &newGeometry);
     static void handleScreenAvailableGeometryChange(QScreen *screen, const QRect &newAvailableGeometry);
     static void handleScreenLogicalDotsPerInchChange(QScreen *screen, qreal newDpiX, qreal newDpiY);
+    static void handleScreenRefreshRateChange(QScreen *screen, qreal newRefreshRate);
 
     static void handleThemeChange(QWindow *tlw);
 
diff --git a/src/gui/kernel/qwindowsysteminterface_qpa_p.h b/src/gui/kernel/qwindowsysteminterface_qpa_p.h
index d7be7699e9..c7ad197b3c 100644
--- a/src/gui/kernel/qwindowsysteminterface_qpa_p.h
+++ b/src/gui/kernel/qwindowsysteminterface_qpa_p.h
@@ -66,6 +66,7 @@ public:
         ScreenGeometry,
         ScreenAvailableGeometry,
         ScreenLogicalDotsPerInch,
+        ScreenRefreshRate,
         ThemeChange,
         Expose
     };
@@ -233,6 +234,14 @@ public:
         qreal dpiY;
     };
 
+    class ScreenRefreshRateEvent : public WindowSystemEvent {
+    public:
+        ScreenRefreshRateEvent(QScreen *s, qreal r)
+            : WindowSystemEvent(ScreenRefreshRate), screen(s), rate(r) { }
+        QWeakPointer<QScreen> screen;
+        qreal rate;
+    };
+
     class ThemeChangeEvent : public WindowSystemEvent {
     public:
         explicit ThemeChangeEvent(QWindow * w)