5 files changed, 61 insertions, 2 deletions

diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index 7155127f75..7bfc9ccbec 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -1591,6 +1591,8 @@ void QGuiApplicationPrivate::processActivatedEvent(QWindowSystemInterfacePrivate
     }
 
     QGuiApplicationPrivate::focus_window = newFocus;
+    if (!qApp)
+        return;
 
     if (previous) {
         QFocusEvent focusOut(QEvent::FocusOut);
diff --git a/src/gui/kernel/qplatformwindow.cpp b/src/gui/kernel/qplatformwindow.cpp
index 1eec6bfefc..bfb6ab5a68 100644
--- a/src/gui/kernel/qplatformwindow.cpp
+++ b/src/gui/kernel/qplatformwindow.cpp
@@ -41,11 +41,13 @@
 
 #include "qplatformwindow.h"
 #include "qplatformwindow_p.h"
+#include "qplatformscreen.h"
 
 #include <private/qguiapplication_p.h>
 #include <qpa/qwindowsysteminterface.h>
 #include <QtGui/qwindow.h>
 #include <QtGui/qscreen.h>
+#include <private/qwindow_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -461,6 +463,43 @@ QString QPlatformWindow::formatWindowTitle(const QString &title, const QString &
 }
 
 /*!
+    Helper function to get initial geometry on windowing systems which do not
+    do smart positioning and also do not provide a means of centering a
+    transient window w.r.t. its parent. For example this is useful on Windows
+    and MacOS but not X11, because an X11 window manager typically tries to
+    layout new windows to optimize usage of the available desktop space.
+    However if the given window already has geometry which the application has
+    initialized, it takes priority.
+*/
+QRect QPlatformWindow::initialGeometry(const QWindow *w,
+    const QRect &initialGeometry, int defaultWidth, int defaultHeight)
+{
+    QRect rect(initialGeometry);
+    if (rect.isNull()) {
+        QSize minimumSize = w->minimumSize();
+        if (minimumSize.width() > 0 || minimumSize.height() > 0) {
+            rect.setSize(minimumSize);
+        } else {
+            rect.setWidth(defaultWidth);
+            rect.setHeight(defaultHeight);
+        }
+    }
+    if (w->isTopLevel() && qt_window_private(const_cast<QWindow*>(w))->positionAutomatic) {
+        const QWindow *tp = w->transientParent();
+        if (tp) {
+            // A transient window should be centered w.r.t. its transient parent.
+            rect.moveCenter(tp->geometry().center());
+        } else {
+            // Center the window on the screen.  (Only applicable on platforms
+            // which do not provide a better way.)
+            QPlatformScreen *scr = QPlatformScreen::platformScreenForWindow(w);
+            rect.moveCenter(scr->availableGeometry().center());
+        }
+    }
+    return rect;
+}
+
+/*!
     \class QPlatformWindow
     \since 4.8
     \internal
diff --git a/src/gui/kernel/qplatformwindow.h b/src/gui/kernel/qplatformwindow.h
index e3e460b54c..7ade461890 100644
--- a/src/gui/kernel/qplatformwindow.h
+++ b/src/gui/kernel/qplatformwindow.h
@@ -128,6 +128,9 @@ public:
     virtual void setFrameStrutEventsEnabled(bool enabled);
     virtual bool frameStrutEventsEnabled() const;
 
+    static QRect initialGeometry(const QWindow *w,
+        const QRect &initialGeometry, int defaultWidth, int defaultHeight);
+
 protected:
     static QString formatWindowTitle(const QString &title, const QString &separator);
 
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 33fd4954eb..99a54dc847 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -129,6 +129,18 @@ QT_BEGIN_NAMESPACE
     and can keep rendering until it isExposed() returns false. To find out when
     isExposed() changes, reimplement exposeEvent(). The window will always get
     a resize event before the first expose event.
+
+    \section1 Initial geometry
+
+    If the window's width and height are left uninitialized, the window will
+    get a reasonable default geometry from the platform window. If the position
+    is left uninitialized, then the platform window will allow the windowing
+    system to position the window. For example on X11, the window manager
+    usually does some kind of smart positioning to try to avoid having new
+    windows completely obscure existing windows. However setGeometry()
+    initializes both the position and the size, so if you want a fixed size but
+    an automatic position, you should call resize() or setWidth() and
+    setHeight() instead.
 */
 
 /*!
@@ -1125,7 +1137,7 @@ void QWindow::setY(int arg)
 void QWindow::setWidth(int arg)
 {
     if (width() != arg)
-        setGeometry(QRect(x(), y(), arg, height()));
+        resize(arg, height());
 }
 
 /*!
@@ -1135,7 +1147,7 @@ void QWindow::setWidth(int arg)
 void QWindow::setHeight(int arg)
 {
     if (height() != arg)
-        setGeometry(QRect(x(), y(), width(), arg));
+        resize(width(), arg);
 }
 
 /*!
@@ -1258,6 +1270,7 @@ void QWindow::setGeometry(int posx, int posy, int w, int h)
 void QWindow::setGeometry(const QRect &rect)
 {
     Q_D(QWindow);
+    d->positionAutomatic = false;
     if (rect == geometry())
         return;
     QRect oldRect = geometry();
diff --git a/src/gui/kernel/qwindow_p.h b/src/gui/kernel/qwindow_p.h
index e92f37c34f..e32d45acca 100644
--- a/src/gui/kernel/qwindow_p.h
+++ b/src/gui/kernel/qwindow_p.h
@@ -87,6 +87,7 @@ public:
         , resizeEventPending(true)
         , receivedExpose(false)
         , positionPolicy(WindowFrameExclusive)
+        , positionAutomatic(true)
         , contentOrientation(Qt::PrimaryOrientation)
         , opacity(qreal(1.0))
         , minimumSize(0, 0)
@@ -141,6 +142,7 @@ public:
     bool resizeEventPending;
     bool receivedExpose;
     PositionPolicy positionPolicy;
+    bool positionAutomatic;
     Qt::ScreenOrientation contentOrientation;
     qreal opacity;
     QRegion mask;