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69 lines
3.3 KiB
69 lines
3.3 KiB
13 years ago
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<title>Object Trees and Object Ownership</title>
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<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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<p> <a href="qobject.html">TQObjects</a> organize themselves in object trees.
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When you create a <a href="qobject.html">TQObject</a> with another object as parent, it's added to
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the parent's <a href="qobject.html#children">children()</a> list, and
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is deleted when the parent is. It turns out that this approach fits
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the needs of GUI objects very well. For example, a <a href="qaccel.html">TQAccel</a> (keyboard
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accelerator) is a child of the relevant window, so when the user closes
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that window, the accelerator is deleted too.
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<p> The static function <a href="qobject.html#objectTrees">TQObject::objectTrees</a>() provides access to all
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the root objects that currently exist.
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<p> <a href="qwidget.html">TQWidget</a>, the base class of everything that appears on the screen,
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extends the parent-child relationship. A child normally also becomes a
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child widget, i.e. it is displayed in its parent's coordinate system
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and is graphically clipped by its parent's boundaries. For example,
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when the an application deletes a message box after it has been
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closed, the message box's buttons and label are also deleted, just as
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we'd want, because the buttons and label are children of the message
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box.
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<p> You can also delete child objects yourself, and they will remove
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themselves from their parents. For example, when the user removes a
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toolbar it may lead to the application deleting one of its <a href="qtoolbar.html">TQToolBar</a>
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objects, in which case the tool bar's <a href="qmainwindow.html">TQMainWindow</a> parent would
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detect the change and reconfigure its screen space accordingly.
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<p> The debugging functions <a href="qobject.html#dumpObjectTree">TQObject::dumpObjectTree</a>() and <a href="qobject.html#dumpObjectInfo">TQObject::dumpObjectInfo</a>() are often useful when an application looks or
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acts strangely.
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<p>
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<p><address><hr><div align=center>
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<table width=100% cellspacing=0 border=0><tr>
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<td>Copyright © 2007
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<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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<td align=right><div align=right>TQt 3.3.8</div>
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