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| 32 | <td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Object Trees and Object Ownership</h1>
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| 33 |
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| 34 |
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| 35 |
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| 36 | <p> <a href="qobject.html">QObjects</a> organize themselves in object trees.
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| 37 | When you create a <a href="qobject.html">QObject</a> with another object as parent, it's added to
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| 38 | the parent's <a href="qobject.html#children">children()</a> list, and
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| 39 | is deleted when the parent is. It turns out that this approach fits
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| 40 | the needs of GUI objects very well. For example, a <a href="qaccel.html">QAccel</a> (keyboard
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| 41 | accelerator) is a child of the relevant window, so when the user closes
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| 42 | that window, the accelerator is deleted too.
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| 43 | <p> The static function <a href="qobject.html#objectTrees">QObject::objectTrees</a>() provides access to all
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| 44 | the root objects that currently exist.
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| 45 | <p> <a href="qwidget.html">QWidget</a>, the base class of everything that appears on the screen,
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| 46 | extends the parent-child relationship. A child normally also becomes a
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| 47 | child widget, i.e. it is displayed in its parent's coordinate system
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| 48 | and is graphically clipped by its parent's boundaries. For example,
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| 49 | when the an application deletes a message box after it has been
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| 50 | closed, the message box's buttons and label are also deleted, just as
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| 51 | we'd want, because the buttons and label are children of the message
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| 52 | box.
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| 53 | <p> You can also delete child objects yourself, and they will remove
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| 54 | themselves from their parents. For example, when the user removes a
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| 55 | toolbar it may lead to the application deleting one of its <a href="qtoolbar.html">QToolBar</a>
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| 56 | objects, in which case the tool bar's <a href="qmainwindow.html">QMainWindow</a> parent would
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| 57 | detect the change and reconfigure its screen space accordingly.
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| 58 | <p> The debugging functions <a href="qobject.html#dumpObjectTree">QObject::dumpObjectTree</a>() and <a href="qobject.html#dumpObjectInfo">QObject::dumpObjectInfo</a>() are often useful when an application looks or
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| 59 | acts strangely.
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| 60 | <p>
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| 64 | <td>Copyright © 2007
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| 65 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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| 66 | <td align=right><div align=right>Qt 3.3.8</div>
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| 67 | </table></div></address></body>
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