From bd0f3345a938b35ce6a12f6150373b0955b8dd12 Mon Sep 17 00:00:00 2001 From: Timothy Pearson Date: Sun, 10 Jul 2011 15:24:15 -0500 Subject: Add Qt3 development HEAD version --- doc/html/objecttrees.html | 68 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 68 insertions(+) create mode 100644 doc/html/objecttrees.html (limited to 'doc/html/objecttrees.html') diff --git a/doc/html/objecttrees.html b/doc/html/objecttrees.html new file mode 100644 index 0000000..40b340a --- /dev/null +++ b/doc/html/objecttrees.html @@ -0,0 +1,68 @@ + + + + + +Object Trees and Object Ownership + + + + + + + +

Object Trees and Object Ownership

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QObjects organize themselves in object trees. +When you create a QObject with another object as parent, it's added to +the parent's children() list, and +is deleted when the parent is. It turns out that this approach fits +the needs of GUI objects very well. For example, a QAccel (keyboard +accelerator) is a child of the relevant window, so when the user closes +that window, the accelerator is deleted too. +

The static function QObject::objectTrees() provides access to all +the root objects that currently exist. +

QWidget, the base class of everything that appears on the screen, +extends the parent-child relationship. A child normally also becomes a +child widget, i.e. it is displayed in its parent's coordinate system +and is graphically clipped by its parent's boundaries. For example, +when the an application deletes a message box after it has been +closed, the message box's buttons and label are also deleted, just as +we'd want, because the buttons and label are children of the message +box. +

You can also delete child objects yourself, and they will remove +themselves from their parents. For example, when the user removes a +toolbar it may lead to the application deleting one of its QToolBar +objects, in which case the tool bar's QMainWindow parent would +detect the change and reconfigure its screen space accordingly. +

The debugging functions QObject::dumpObjectTree() and QObject::dumpObjectInfo() are often useful when an application looks or +acts strangely. +

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Trademarks +

Qt 3.3.8

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