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<td align="right" valign="top" width="230"><img src="images/trolltech-logo.png" align="right" width="203" height="32" border="0" /></td></tr></table><h1 align="center">Window Geometry</h1>

<p><a href="qwidget.html">QWidget</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> <a href="qwidget.html#x-prop">x()</a>, <a href="qwidget.html#y-prop">y()</a>, <a href="qwidget.html#frameGeometry-prop">frameGeometry()</a>, <a href="qwidget.html#pos-prop">pos()</a>, and <a href="qwidget.html#pos-prop">move()</a>.</li>

<li><b>Excluding the window frame:</b> <a href="qwidget.html#geometry-prop">geometry()</a>, <a href="qwidget.html#width-prop">width()</a>, <a href="qwidget.html#height-prop">height()</a>, <a href="qwidget.html#rect-prop">rect()</a>, and <a href="qwidget.html#size-prop">size()</a>.</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: <center><img src="images/geometry.png" alt="Geometry diagram" /></center></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>

<h2>X11 Peculiarities</h2>

<p>On <a href="winsystem.html#x11">X11</a>, a window does not have a frame until the window manager decorates it. This happens asynchronously at some point in time after calling <a href="qwidget.html#show">QWidget::show</a>() and the first paint event the window receives, or it does not happen at all. Bear in mind that <a href="winsystem.html#x11">X11</a> 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><a href="winsystem.html#x11">X11</a> 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 <a href="qwidget.html#frameGeometry-prop">QWidget::frameGeometry</a>() returns wrong results though.</p>

<p>Nor does <a href="winsystem.html#x11">X11</a> provide a way to maximize a window. <a href="qwidget.html#showMaximized">QWidget::showMaximized</a>() has to emulate the feature. Its result depends on the result of <a href="qwidget.html#frameGeometry-prop">QWidget::frameGeometry</a>() and the capability of the window manager to do proper window placement, neither of which can be guaranteed.</p>

<h2>Restoring a Window's Geometry</h2>

<p>A common task in modern applications is to restore a window's geometry in a later session. On Windows, this is basically storing the result of <a href="qwidget.html#geometry-prop">QWidget::geometry</a>() and calling <a href="qwidget.html#geometry-prop">QWidget::setGeometry</a>() in the next session before calling <a href="qwidget.html#show">show()</a>. On <a href="winsystem.html#x11">X11</a>, 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, our tests have shown that almost all window managers fail to implement this feature.</p>

<p>A workaround is to call <a href="qwidget.html#geometry-prop">setGeometry()</a> after <a href="qwidget.html#show">show()</a>. 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 <a href="qwidget.html#pos-prop">pos()</a> and <a href="qwidget.html#size-prop">size()</a> and to restore the geometry using <a href="qwidget.html#size-prop">QWidget::resize</a>() and <a href="qwidget.html#pos-prop">move()</a> before calling <a href="qwidget.html#show">show()</a>, as demonstrated in the following code snippets (from the <a href="mainwindows-application.html">Application</a> 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 both Microsoft Windows and most existing <a href="winsystem.html#x11">X11</a> window managers.</p>

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