Re-implement transient window support in XCB backend.

If a QWindow has a parent but is top-level the corresponding
QPlatformWindow should not be re-parented but instead be made transient
for the parent window if possible.

src/gui/kernel/qplatformwindow_qpa.cpp

@@ -70,7 +70,7 @@ QPlatformWindow::~QPlatformWindow()
 }
 
 /*!
-    Returnes the window which belongs to the QPlatformWindow
+    Returns the window which belongs to the QPlatformWindow
 */
 QWindow *QPlatformWindow::window() const
 {
@@ -78,6 +78,15 @@ QWindow *QPlatformWindow::window() const
     return d->window;
 }
 
+/*!
+    Returns the parent platform window (or 0 if orphan).
+*/
+QPlatformWindow *QPlatformWindow::parent() const
+{
+    Q_D(const QPlatformWindow);
+    return d->window->parent() ? d->window->parent()->handle() : 0;
+}
+
 /*!
     This function is called by Qt whenever a window is moved or the window is resized. The resize
     can happen programatically(from ie. user application) or by the window manager. This means that

src/gui/kernel/qplatformwindow_qpa.h

@@ -66,6 +66,8 @@ public:
     virtual ~QPlatformWindow();
 
     QWindow *window() const;
+    QPlatformWindow *parent() const;
+
     virtual void setGeometry(const QRect &rect);
     virtual QRect geometry() const;
 

src/gui/kernel/qwindow.cpp

@@ -97,7 +97,7 @@ void QWindow::create()
             QObject *object = childObjects.at(i);
             if(object->isWindowType()) {
                 QWindow *window = static_cast<QWindow *>(object);
-                if (window->d_func()->platformWindow)
+                if (window->d_func()->platformWindow && !window->isTopLevel())
                     window->d_func()->platformWindow->setParent(d->platformWindow);
             }
         }
@@ -133,9 +133,9 @@ void QWindow::setParent(QWindow *parent)
     QObject::setParent(parent);
 
     if (d->platformWindow) {
-        if (parent && parent->d_func()->platformWindow) {
+        if (parent && parent->d_func()->platformWindow && !isTopLevel()) {
             d->platformWindow->setParent(parent->d_func()->platformWindow);
-        } else if (!parent) {
+        } else {
             d->platformWindow->setParent(0);
         }
     }
@@ -144,12 +144,12 @@ void QWindow::setParent(QWindow *parent)
 }
 
 /*!
-   Returns whether the window is top level, i.e. parent-less.
+   Returns whether the window is top level.
  */
 bool QWindow::isTopLevel() const
 {
     Q_D(const QWindow);
-    return d->parentWindow == 0;
+    return d->windowFlags & Qt::Window;
 }
 
 void QWindow::setWindowFormat(const QWindowFormat &format)
@@ -196,6 +196,12 @@ Qt::WindowFlags QWindow::windowFlags() const
     return d->windowFlags;
 }
 
+Qt::WindowType QWindow::windowType() const
+{
+    Q_D(const QWindow);
+    return static_cast<Qt::WindowType>(int(d->windowFlags & Qt::WindowType_Mask));
+}
+
 void QWindow::setWindowTitle(const QString &title)
 {
     Q_D(QWindow);

src/gui/kernel/qwindow.h

@@ -107,6 +107,7 @@ public:
 
     void setWindowFlags(Qt::WindowFlags flags);
     Qt::WindowFlags windowFlags() const;
+    Qt::WindowType windowType() const;
 
     QString windowTitle() const;
 

src/plugins/platforms/xcb/qxcbwindow.cpp

@@ -73,20 +73,17 @@
 #include "../eglconvenience/qxlibeglintegration.h"
 #endif
 
-#if 0
 // Returns true if we should set WM_TRANSIENT_FOR on \a w
-static inline bool isTransient(const QWidget *w)
+static inline bool isTransient(const QWindow *w)
 {
-    return ((w->windowType() == Qt::Dialog
+    return w->windowType() == Qt::Dialog
-             || w->windowType() == Qt::Sheet
+           || w->windowType() == Qt::Sheet
-             || w->windowType() == Qt::Tool
+           || w->windowType() == Qt::Tool
-             || w->windowType() == Qt::SplashScreen
+           || w->windowType() == Qt::SplashScreen
-             || w->windowType() == Qt::ToolTip
+           || w->windowType() == Qt::ToolTip
-             || w->windowType() == Qt::Drawer
+           || w->windowType() == Qt::Drawer
-             || w->windowType() == Qt::Popup)
+           || w->windowType() == Qt::Popup;
-            && !w->testAttribute(Qt::WA_X11BypassTransientForHint));
 }
-#endif
 
 QXcbWindow::QXcbWindow(QWindow *window)
     : QPlatformWindow(window)
@@ -119,8 +116,8 @@ QXcbWindow::QXcbWindow(QWindow *window)
     QRect rect = window->geometry();
 
     xcb_window_t xcb_parent_id = m_screen->root();
-    if (window->parent() && window->parent()->handle())
+    if (parent() && !window->isTopLevel())
-        xcb_parent_id = static_cast<QXcbWindow *>(window->parent()->handle())->xcb_window();
+        xcb_parent_id = static_cast<QXcbWindow *>(parent())->xcb_window();
 
 #if defined(XCB_USE_GLX) || defined(XCB_USE_EGL)
     if (window->surfaceType() == QWindow::OpenGLSurface
@@ -217,18 +214,6 @@ QXcbWindow::QXcbWindow(QWindow *window)
                                        &m_syncCounter));
     }
 
-#if 0
-    if (tlw && isTransient(tlw) && tlw->parentWidget()) {
-        // ICCCM 4.1.2.6
-        QWidget *p = tlw->parentWidget()->window();
-        xcb_window_t parentWindow = p->winId();
-        Q_XCB_CALL(xcb_change_property(xcb_connection(), XCB_PROP_MODE_REPLACE, m_window,
-                                       XCB_ATOM_WM_TRANSIENT_FOR, XCB_ATOM_WINDOW, 32,
-                                       1, &parentWindow));
-
-    }
-#endif
-
     // set the PID to let the WM kill the application if unresponsive
     long pid = getpid();
     Q_XCB_CALL(xcb_change_property(xcb_connection(), XCB_PROP_MODE_REPLACE, m_window,
@@ -278,7 +263,19 @@ void QXcbWindow::show()
 
         xcb_set_wm_hints(xcb_connection(), m_window, &hints);
 
+        // update WM_NORMAL_HINTS
         propagateSizeHints();
+
+        // update WM_TRANSIENT_FOR
+        if (isTransient(window()) && parent()) {
+            // ICCCM 4.1.2.6
+            xcb_window_t parentWindow = static_cast<QXcbWindow *>(parent())->xcb_window();
+
+            // todo: set transient for group (wm_client_leader) if no parent, a la qwidget_x11.cpp
+            Q_XCB_CALL(xcb_change_property(xcb_connection(), XCB_PROP_MODE_REPLACE, m_window,
+                                           XCB_ATOM_WM_TRANSIENT_FOR, XCB_ATOM_WINDOW, 32,
+                                           1, &parentWindow));
+        }
     }
 
     Q_XCB_CALL(xcb_map_window(xcb_connection(), m_window));
@@ -598,6 +595,7 @@ void QXcbWindow::lower()
 
 void QXcbWindow::propagateSizeHints()
 {
+    // update WM_NORMAL_HINTS
     xcb_size_hints_t hints;
 
     QRect rect = geometry();

src/widgets/kernel/qwidget_qpa.cpp

@@ -93,11 +93,9 @@ void QWidgetPrivate::create_sys(WId window, bool initializeWindow, bool destroyO
 
     QWindow *win = topData()->window;
 
-    if (!q->isWindow()) {
+    if (QWidget *nativeParent = q->nativeParentWidget()) {
-        if (QWidget *nativeParent = q->nativeParentWidget()) {
+        if (nativeParent->windowHandle())
-            if (nativeParent->windowHandle())
+            win->setParent(nativeParent->windowHandle());
-                win->setParent(nativeParent->windowHandle());
-        }
     }
 
     win->setWindowFlags(data.window_flags);