Page flipping API for QPlatformScreen

Adding a page flipping API for platform plugins. This
enables Wayland compositors to show full-screen client windows directly
without copying any data - if supported by the platform.

Change-Id: I19abe366434140f9e20a0655fe7cd41ea9264fca
Reviewed-on: http://codereview.qt-project.org/5385
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Jørgen Lind <jorgen.lind@nokia.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/src/gui/kernel/qplatformscreen_qpa.cpp b/src/gui/kernel/qplatformscreen_qpa.cpp
index 8fb42595b8..e25e3f33d3 100644
--- a/src/gui/kernel/qplatformscreen_qpa.cpp
+++ b/src/gui/kernel/qplatformscreen_qpa.cpp
@@ -181,3 +181,41 @@ QPlatformScreen * QPlatformScreen::platformScreenForWindow(const QWindow *window
     Reimplement in subclass to return the image format which corresponds to the screen format
 */
 
+
+/*!
+    \class QPlatformScreenPageFlipper
+    \since 5.0
+    \internal
+    \preliminary
+    \ingroup qpa
+
+    \brief The QPlatformScreenPageFlipper class provides an abstract interface for display buffer swapping
+
+    Implement the displayBuffer() function to initiate a buffer swap. The
+    bufferDisplayed() signal should be emitted once the buffer is actually displayed on
+    the screen. The bufferReleased() signal should be emitted when the buffer data is no
+    longer owned by the display hardware.
+*/
+
+/*!  \fn bool QPlatformScreenPageFlipper::displayBuffer(void *bufferHandle)
+
+Implemented in subclasses to display the buffer referenced by \a bufferHandle directly on
+the screen. Returns \c true if it is possible to display the buffer, and \c false if the
+buffer cannot be displayed.
+
+If this function returns true, the buffer must not be modified or destroyed before the
+bufferReleased() signal is emitted.  The signal bufferDisplayed() is emitted when the buffer
+is displayed on the screen. The two signals may be emitted in either order.
+
+This function is allowed to block.
+*/
+
+
+/*!
+  Implemented in subclasses to return a page flipper object for the screen, or 0 if the
+  hardware does not support page flipping. The default implementation returns 0.
+ */
+QPlatformScreenPageFlipper *QPlatformScreen::pageFlipper() const
+{
+    return 0;
+}