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+
+/*!
+ \example dialogs/extension
+ \title Extension Example
+
+ The Extension example shows how to add an extension to a QDialog
+ using the QAbstractButton::toggled() signal and the
+ QWidget::setVisible() slot.
+
+ \image extension-example.png Screenshot of the Extension example
+
+ The Extension application is a dialog that allows the user to
+ perform a simple search as well as a more advanced search.
+
+ The simple search has two options: \gui {Match case} and \gui
+ {Search from start}. The advanced search options include the
+ possibilities to search for \gui {Whole words}, \gui {Search
+ backward} and \gui {Search selection}. Only the simple search is
+ visible when the application starts. The advanced search options
+ are located in the application's extension part, and can be made
+ visible by pressing the \gui More button:
+
+ \image extension_more.png Screenshot of the Extension example
+
+ \section1 FindDialog Class Definition
+
+ The \c FindDialog class inherits QDialog. The QDialog class is the
+ base class of dialog windows. A dialog window is a top-level
+ window mostly used for short-term tasks and brief communications
+ with the user.
+
+ \snippet examples/dialogs/extension/finddialog.h 0
+
+ The \c FindDialog widget is the main application widget, and
+ displays the application's search options and controlling
+ buttons.
+
+ In addition to a constructor, we declare the several child
+ widgets: We need a QLineEdit with an associated QLabel to let the
+ user type a word to search for, we need several \l
+ {QCheckBox}{QCheckBox}es to facilitate the search options, and we
+ need three \l {QPushButton}{QPushButton}s: the \gui Find button to
+ start a search and the \gui More button to enable an advanced search.
+ Finally, we need a QWidget representing the application's extension
+ part.
+
+ \section1 FindDialog Class Implementation
+
+ In the constructor we first create the standard child widgets for
+ the simple search: the QLineEdit with the associated QLabel, two
+ of the \l {QCheckBox}{QCheckBox}es and all the \l
+ {QPushButton}{QPushButton}s.
+
+ \snippet examples/dialogs/extension/finddialog.cpp 0
+
+ We give the options and buttons a shortcut key using the &
+ character. In the \gui {Find what} option's case, we also need to
+ use the QLabel::setBuddy() function to make the shortcut key work
+ as expected; then, when the user presses the shortcut key
+ indicated by the label, the keyboard focus is transferred to the
+ label's buddy widget, the QLineEdit.
+
+ We set the \gui Find button's default property to true, using the
+ QPushButton::setDefault() function. Then the push button will be
+ pressed if the user presses the Enter (or Return) key. Note that a
+ QDialog can only have one default button.
+
+ \snippet examples/dialogs/extension/finddialog.cpp 2
+
+ Then we create the extension widget, and the \l
+ {QCheckBox}{QCheckBox}es associated with the advanced search
+ options.
+
+ \snippet examples/dialogs/extension/finddialog.cpp 3
+
+ Now that the extension widget is created, we can connect the \gui
+ More button's \l{QAbstractButton::toggled()}{toggled()} signal to
+ the extension widget's \l{QWidget::setVisible()}{setVisible()} slot.
+
+ The QAbstractButton::toggled() signal is emitted whenever a
+ checkable button changes its state. The signal's argument is true
+ if the button is checked, or false if the button is unchecked. The
+ QWidget::setVisible() slot sets the widget's visible status. If
+ the status is true the widget is shown, otherwise the widget is
+ hidden.
+
+ Since we made the \gui More button checkable when we created it,
+ the connection makes sure that the extension widget is shown
+ depending on the state of \gui More button.
+
+ We also put the check boxes associated with the advanced
+ search options into a layout we install on the extension widget.
+
+ \snippet examples/dialogs/extension/finddialog.cpp 4
+
+ Before we create the main layout, we create several child layouts
+ for the widgets: First we allign the QLabel ans its buddy, the
+ QLineEdit, using a QHBoxLayout. Then we vertically allign the
+ QLabel and QLineEdit with the check boxes associated with the
+ simple search, using a QVBoxLayout. We also create a QVBoxLayout
+ for the buttons. In the end we lay out the two latter layouts and
+ the extension widget using a QGridLayout.
+
+ \snippet examples/dialogs/extension/finddialog.cpp 5
+
+ Finally, we hide the extension widget using the QWidget::hide()
+ function, making the application only show the simple search
+ options when it starts. When the user wants to access the advanced
+ search options, the dialog only needs to change the visibility of
+ the extension widget. Qt's layout management takes care of the
+ dialog's appearance.
+*/