Transient QWindows centered; default-constructed geometry

Default-constructed geometry does not mean put the window at 0,0,
and it does not mean center the window on the screen: it means
let the window manager position the window.  If the window is
explicitly positioned at 0,0 though, that is a higher priority
than the transient hint; without this change, the transientFor property
had no effect.  On X11, transient means use center "gravity" to
make the transient window exactly centered.  But the user can still
override the geometry of a transient window, as with any window.
On OSX and Windows, neither transient window functionality nor smart
initial positioning are provided, so a window with no position set
will be centered on the screen, and a transient window will be put
at the center of its transientParent.

Change-Id: I4f5e37480eef5d105e45ffd60362a57f13ec55f5
Task-number: QTBUG-26903
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>

3 files changed, 53 insertions, 16 deletions

diff --git a/src/plugins/platforms/cocoa/qcocoawindow.mm b/src/plugins/platforms/cocoa/qcocoawindow.mm
index 489c229187..2adf0d24a1 100644
--- a/src/plugins/platforms/cocoa/qcocoawindow.mm
+++ b/src/plugins/platforms/cocoa/qcocoawindow.mm
@@ -58,6 +58,11 @@
 
 #include <QDebug>
 
+enum {
+    defaultWindowWidth = 160,
+    defaultWindowHeight = 160
+};
+
 static bool isMouseEvent(NSEvent *ev)
 {
     switch ([ev type]) {
@@ -683,7 +688,8 @@ NSWindow * QCocoaWindow::createNSWindow()
 {
     QCocoaAutoReleasePool pool;
 
-    NSRect frame = qt_mac_flipRect(window()->geometry(), window());
+    QRect rect = initialGeometry(window(), window()->geometry(), defaultWindowWidth, defaultWindowHeight);
+    NSRect frame = qt_mac_flipRect(rect, window());
 
     Qt::WindowType type = window()->type();
     Qt::WindowFlags flags = window()->flags();
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 07dc668b3f..20000ea0a9 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -64,6 +64,11 @@
 
 QT_BEGIN_NAMESPACE
 
+enum {
+    defaultWindowWidth = 160,
+    defaultWindowHeight = 160
+};
+
 Q_GUI_EXPORT HICON qt_pixmapToWinHICON(const QPixmap &);
 
 static QByteArray debugWinStyle(DWORD style)
@@ -468,6 +473,8 @@ QWindowsWindow::WindowData
 
     const QString windowClassName = QWindowsContext::instance()->registerWindowClass(w, isGL);
 
+    QRect rect = QPlatformWindow::initialGeometry(w, geometry, defaultWindowWidth, defaultWindowHeight);
+
     if (title.isEmpty() && (result.flags & Qt::WindowTitleHint))
         title = topLevel ? qAppName() : w->objectName();
 
@@ -475,14 +482,14 @@ QWindowsWindow::WindowData
     const wchar_t *classNameUtf16 = reinterpret_cast<const wchar_t *>(windowClassName.utf16());
 
     // Capture events before CreateWindowEx() returns.
-    const QWindowCreationContextPtr context(new QWindowCreationContext(w, geometry, style, exStyle));
+    const QWindowCreationContextPtr context(new QWindowCreationContext(w, rect, style, exStyle));
     QWindowsContext::instance()->setWindowCreationContext(context);
 
     if (QWindowsContext::verboseWindows)
         qDebug().nospace()
                 << "CreateWindowEx: " << w << *this
                 << " class=" <<windowClassName << " title=" << title
-                << "\nrequested: " << geometry << ": "
+                << "\nrequested: " << rect << ": "
                 << context->frameWidth << 'x' <<  context->frameHeight
                 << '+' << context->frameX << '+' << context->frameY;
 
@@ -775,6 +782,7 @@ QWindowsWindow::QWindowsWindow(QWindow *aWindow, const WindowData &data) :
 QWindowsWindow::~QWindowsWindow()
 {
 #ifndef Q_OS_WINCE
+    QWindowSystemInterface::flushWindowSystemEvents();
     if (QWindowsContext::instance()->systemInfo() & QWindowsContext::SI_SupportsTouch)
         QWindowsContext::user32dll.unregisterTouchWindow(m_data.hwnd);
 #endif // !Q_OS_WINCE
diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index c0ddf5c0ae..abd2f7a147 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -113,6 +113,10 @@
 #endif
 
 #define XCOORD_MAX 16383
+enum {
+    defaultWindowWidth = 160,
+    defaultWindowHeight = 160
+};
 
 //#ifdef NET_WM_STATE_DEBUG
 
@@ -219,8 +223,16 @@ void QXcbWindow::create()
     QRect rect = window()->geometry();
     QPlatformWindow::setGeometry(rect);
 
-    rect.setWidth(qBound(1, rect.width(), XCOORD_MAX));
-    rect.setHeight(qBound(1, rect.height(), XCOORD_MAX));
+    QSize minimumSize = window()->minimumSize();
+    if (rect.width() > 0 || rect.height() > 0) {
+        rect.setWidth(qBound(1, rect.width(), XCOORD_MAX));
+        rect.setHeight(qBound(1, rect.height(), XCOORD_MAX));
+    } else if (minimumSize.width() > 0 || minimumSize.height() > 0) {
+        rect.setSize(minimumSize);
+    } else {
+        rect.setWidth(defaultWindowWidth);
+        rect.setHeight(defaultWindowHeight);
+    }
 
     xcb_window_t xcb_parent_id = m_screen->root();
     if (parent())
@@ -436,15 +448,23 @@ void QXcbWindow::setGeometry(const QRect &rect)
     propagateSizeHints();
     const QRect wmGeometry = windowToWmGeometry(rect);
 
-    const quint32 mask = XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y | XCB_CONFIG_WINDOW_WIDTH | XCB_CONFIG_WINDOW_HEIGHT;
-    const qint32 values[] = {
-        qBound<qint32>(-XCOORD_MAX, wmGeometry.x(),      XCOORD_MAX),
-        qBound<qint32>(-XCOORD_MAX, wmGeometry.y(),      XCOORD_MAX),
-        qBound<qint32>(1,           wmGeometry.width(),  XCOORD_MAX),
-        qBound<qint32>(1,           wmGeometry.height(), XCOORD_MAX),
-    };
-
-    Q_XCB_CALL(xcb_configure_window(xcb_connection(), m_window, mask, reinterpret_cast<const quint32*>(values)));
+    if (qt_window_private(window())->positionAutomatic) {
+        const quint32 mask = XCB_CONFIG_WINDOW_WIDTH | XCB_CONFIG_WINDOW_HEIGHT;
+        const qint32 values[] = {
+            qBound<qint32>(1,           wmGeometry.width(),  XCOORD_MAX),
+            qBound<qint32>(1,           wmGeometry.height(), XCOORD_MAX),
+        };
+        Q_XCB_CALL(xcb_configure_window(xcb_connection(), m_window, mask, reinterpret_cast<const quint32*>(values)));
+    } else {
+        const quint32 mask = XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y | XCB_CONFIG_WINDOW_WIDTH | XCB_CONFIG_WINDOW_HEIGHT;
+        const qint32 values[] = {
+            qBound<qint32>(-XCOORD_MAX, wmGeometry.x(),      XCOORD_MAX),
+            qBound<qint32>(-XCOORD_MAX, wmGeometry.y(),      XCOORD_MAX),
+            qBound<qint32>(1,           wmGeometry.width(),  XCOORD_MAX),
+            qBound<qint32>(1,           wmGeometry.height(), XCOORD_MAX),
+        };
+        Q_XCB_CALL(xcb_configure_window(xcb_connection(), m_window, mask, reinterpret_cast<const quint32*>(values)));
+    }
 
     xcb_flush(xcb_connection());
 }
@@ -563,6 +583,7 @@ void QXcbWindow::show()
             if (!transientXcbParent)
                 transientXcbParent = static_cast<QXcbScreen *>(screen())->clientLeader();
             if (transientXcbParent) { // ICCCM 4.1.2.6
+                m_gravity = XCB_GRAVITY_CENTER;
                 Q_XCB_CALL(xcb_change_property(xcb_connection(), XCB_PROP_MODE_REPLACE, m_window,
                                                XCB_ATOM_WM_TRANSIENT_FOR, XCB_ATOM_WINDOW, 32,
                                                1, &transientXcbParent));
@@ -1221,8 +1242,10 @@ void QXcbWindow::propagateSizeHints()
 
     QWindow *win = window();
 
-    xcb_size_hints_set_position(&hints, true, rect.x(), rect.y());
-    xcb_size_hints_set_size(&hints, true, rect.width(), rect.height());
+    if (!qt_window_private(win)->positionAutomatic)
+        xcb_size_hints_set_position(&hints, true, rect.x(), rect.y());
+    if (rect.width() < QWINDOWSIZE_MAX || rect.height() < QWINDOWSIZE_MAX)
+        xcb_size_hints_set_size(&hints, true, rect.width(), rect.height());
     xcb_size_hints_set_win_gravity(&hints, m_gravity);
 
     QSize minimumSize = win->minimumSize();