Clean up QScreen::grabWindow()

Handle 0 WId parameter as meaning "desktop window"/whole screen.
Also, re-add the default values for the grab area, both for
convenience and compatibility with QPixmap::grabWindow() in Qt4.
Update the screenshot example so it doesn't comlain about usage of
deprecated QPixmap::grabWindow().

Change-Id: I2ad229113ddb8ded0388f2ebc0e8c703c6657f1f
Reviewed-by: Gunnar Sletta <gunnar.sletta@nokia.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/src/plugins/platforms/xcb/qxcbscreen.cpp b/src/plugins/platforms/xcb/qxcbscreen.cpp
index 0b362c5256..d92004b1ac 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.cpp
+++ b/src/plugins/platforms/xcb/qxcbscreen.cpp
@@ -277,6 +277,13 @@ QPixmap QXcbScreen::grabWindow(WId window, int x, int y, int width, int height)
     if (width == 0 || height == 0)
         return QPixmap();
 
+    // TODO: handle multiple screens
+    QXcbScreen *screen = const_cast<QXcbScreen *>(this);
+    xcb_window_t root = screen->root();
+
+    if (window == 0)
+        window = root;
+
     xcb_get_geometry_cookie_t geometry_cookie = xcb_get_geometry_unchecked(xcb_connection(), window);
 
     xcb_get_geometry_reply_t *reply =
@@ -291,9 +298,6 @@ QPixmap QXcbScreen::grabWindow(WId window, int x, int y, int width, int height)
     if (height < 0)
         height = reply->height - y;
 
-    // TODO: handle multiple screens
-    QXcbScreen *screen = const_cast<QXcbScreen *>(this);
-    xcb_window_t root = screen->root();
     geometry_cookie = xcb_get_geometry_unchecked(xcb_connection(), root);
     xcb_get_geometry_reply_t *root_reply =
         xcb_get_geometry_reply(xcb_connection(), geometry_cookie, NULL);