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<h1 align="center">Window Geometry<br /><small></small></h1>
<p><a href="gui/QWidget.html"><tt>QWidget</tt></a> provides several functions that deal with a widget's geometry. Some of these functions operate on the pure client area (i.e. the window excluding the window frame), others include the window frame. The differentiation is done in a way that covers the most common usage transparently.</p>
<ul>
<li><b>Including the window frame:</b> x(), y(), frameGeometry(), pos(), and move().</li>
<li><b>Excluding the window frame:</b> geometry(), width(), height(), rect(), and size().</li>
</ul>
<p>Note that the distinction only matters for decorated top-level widgets. For all child widgets, the frame geometry is equal to the widget's client geometry.</p>
<p>This diagram shows most of the functions in use:</p>
<p align="center"><img src="images/geometry.png" alt="Geometry diagram" /></p><p>Topics:</p>
<ul><li><a href="#x11-peculiarities">X11 Peculiarities</a></li>
<li><a href="#restoring-a-window-s-geometry">Restoring a Window's Geometry</a></li>
</ul>
<a name="x11-peculiarities"></a>
<h3>X11 Peculiarities</h3>
<p>On X11, a window does not have a frame until the window manager decorates it. This happens asynchronously at some point in time after calling QWidget::show() and the first paint event the window receives, or it does not happen at all. Bear in mind that X11 is policy-free (others call it flexible). Thus you cannot make any safe assumption about the decoration frame your window will get. Basic rule: There's always one user who uses a window manager that breaks your assumption, and who will complain to you.</p>
<p>Furthermore, a toolkit cannot simply place windows on the screen. All Qt can do is to send certain hints to the window manager. The window manager, a separate process, may either obey, ignore or misunderstand them. Due to the partially unclear Inter-Client Communication Conventions Manual (ICCCM), window placement is handled quite differently in existing window managers.</p>
<p>X11 provides no standard or easy way to get the frame geometry once the window is decorated. Qt solves this problem with nifty heuristics and clever code that works on a wide range of window managers that exist today. Don't be surprised if you find one where QWidget::frameGeometry() returns wrong results though.</p>
<p>Nor does X11 provide a way to maximize a window. QWidget::showMaximized() has to emulate the feature. Its result depends on the result of QWidget::frameGeometry() and the capability of the window manager to do proper window placement, neither of which can be guaranteed.</p>
<a name="restoring-a-window-s-geometry"></a>
<h3>Restoring a Window's Geometry</h3>
<p>Since version 4.2, Qt provides functions that saves and restores a window's geometry and state for you. QWidget::saveGeometry() saves the window geometry and maximized/fullscreen state, while QWidget::restoreGeometry() restores it. The restore function also checks if the restored geometry is outside the available screen geometry, and modifies it as appropriate if it is.</p>
<p>The rest of this document describes how to save and restore the geometry using the geometry properties. On Windows, this is basically storing the result of QWidget::geometry() and calling QWidget::setGeometry() in the next session before calling show(). On X11, this won't work because an invisible window doesn't have a frame yet. The window manager will decorate the window later. When this happens, the window shifts towards the bottom/right corner of the screen depending on the size of the decoration frame. Although X provides a way to avoid this shift, most window managers fail to implement this feature.</p>
<p>A workaround is to call setGeometry() after show(). This has the two disadvantages that the widget appears at a wrong place for a millisecond (results in flashing) and that currently only every second window manager gets it right. A safer solution is to store both pos() and size() and to restore the geometry using <tt>QWidget::resize</tt> and move() before calling show(), as demonstrated in the following code snippets (from the Application</tt> example):</p>
<pre> void MainWindow::readSettings()
{
QSettings settings("Trolltech", "Application Example");
QPoint pos = settings.value("pos", QPoint(200, 200)).toPoint();
QSize size = settings.value("size", QSize(400, 400)).toSize();
resize(size);
move(pos);
}
void MainWindow::writeSettings()
{
QSettings settings("Trolltech", "Application Example");
settings.setValue("pos", pos());
settings.setValue("size", size());
}</pre>
<p>This method works on Windows, Mac OS X, and most X11 window managers.</p>
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