Implemented QXcbScreen::topLevelAt(const QPoint &p).

This makes the tst_QWidget::widgetAt() auto-test pass.

src/plugins/platforms/xcb/qxcbconnection.h

@@ -282,6 +282,8 @@ public:
     template<typename T>
     inline xcb_generic_event_t *checkEvent(const T &checker);
 
+    QXcbWindow *platformWindowFromId(xcb_window_t id);
+
 private slots:
     void processXcbEvents();
 
@@ -291,8 +293,6 @@ private:
 #ifdef XCB_USE_DRI2
     void initializeDri2();
 #endif
-    QXcbWindow *platformWindowFromId(xcb_window_t id);
-
     xcb_connection_t *m_connection;
     const xcb_setup_t *m_setup;
 

src/plugins/platforms/xcb/qxcbintegration.cpp

@@ -215,6 +215,8 @@ QPixmap QXcbIntegration::grabWindow(WId window, int x, int y, int width, int hei
         y = translate_reply->dst_y;
 
         window = root;
+
+        free(translate_reply);
         free(reply);
         reply = root_reply;
     } else {
@@ -338,7 +340,6 @@ QPixmap QXcbIntegration::grabWindow(WId window, int x, int y, int width, int hei
     return result;
 }
 
-
 bool QXcbIntegration::hasOpenGL() const
 {
 #if defined(XCB_USE_GLX)

src/plugins/platforms/xcb/qxcbscreen.cpp

@@ -40,6 +40,7 @@
 ****************************************************************************/
 
 #include "qxcbscreen.h"
+#include "qxcbwindow.h"
 
 #include <stdio.h>
 
@@ -145,6 +146,51 @@ QXcbScreen::~QXcbScreen()
 {
 }
 
+QWindow *QXcbScreen::topLevelAt(const QPoint &p) const
+{
+    xcb_window_t root = m_screen->root;
+
+    int x = p.x();
+    int y = p.y();
+
+    xcb_generic_error_t *error;
+
+    xcb_window_t parent = root;
+    xcb_window_t child = root;
+
+    do {
+        xcb_translate_coordinates_cookie_t translate_cookie =
+            xcb_translate_coordinates(xcb_connection(), parent, child, x, y);
+
+        xcb_translate_coordinates_reply_t *translate_reply =
+            xcb_translate_coordinates_reply(xcb_connection(), translate_cookie, &error);
+
+        if (!translate_reply) {
+            if (error) {
+                connection()->handleXcbError(error);
+                free(error);
+            }
+            return 0;
+        }
+
+        parent = child;
+        child = translate_reply->child;
+        x = translate_reply->dst_x;
+        y = translate_reply->dst_y;
+
+        free(translate_reply);
+
+        if (!child || child == root)
+            return 0;
+
+        QPlatformWindow *platformWindow = connection()->platformWindowFromId(child);
+        if (platformWindow)
+            return platformWindow->window();
+    } while (parent != child);
+
+    return 0;
+}
+
 const xcb_visualtype_t *QXcbScreen::visualForId(xcb_visualid_t visualid) const
 {
     QMap<xcb_visualid_t, xcb_visualtype_t>::const_iterator it = m_visuals.find(visualid);

src/plugins/platforms/xcb/qxcbscreen.h

@@ -57,6 +57,8 @@ public:
     QXcbScreen(QXcbConnection *connection, xcb_screen_t *screen, int number);
     ~QXcbScreen();
 
+    QWindow *topLevelAt(const QPoint &point) const;
+
     QRect geometry() const;
     int depth() const;
     QImage::Format format() const;