Introduced QWindow::isExposed().

The visible property along with show/hideEvent tracks the
windows visibility from the application perspective and is
really a request. The exposeEvent() along with the isExposed()
accessor is used to notify the application of the actual
state of the window in the windowing system.

Change-Id: I7f5b7ed74a168e34aaa21ce0ae9042ddfb0bf6d8
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 96fb394643..5b6ee0e9cb 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -374,6 +374,25 @@ void QWindow::requestActivateWindow()
         d->platformWindow->requestActivateWindow();
 }
 
+
+/*!
+    Returns if this window is exposed in the windowing system.
+
+    When the window is not exposed, it is shown by the application
+    but it is still not showing in the windowing system, so the application
+    should minimize rendering and other graphical activities.
+
+    An exposeEvent() is sent every time this value changes.
+ */
+
+bool QWindow::isExposed() const
+{
+    Q_D(const QWindow);
+    if (d->platformWindow)
+        return d->platformWindow->isExposed();
+    return false;
+}
+
 /*!
     Returns true if the window should appear active from a style perspective.
 
@@ -888,6 +907,19 @@ bool QWindow::close()
     return true;
 }
 
+
+
+/*!
+    The expose event is sent by the window system whenever the window's
+    exposure on screen changes.
+
+    If the window is moved off screen, is made totally obscured by another
+    window, iconified or similar, this function might be called and the
+    value of isExposed() might change to false. When this happens,
+    an application should stop its rendering as it is no longer visible
+    to the user.
+ */
+
 void QWindow::exposeEvent(QExposeEvent *ev)
 {
     ev->ignore();