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+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
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+****************************************************************************/
+
+/*!
+\example widgets/charactermap
+\title Character Map Example
+
+The Character Map example shows how to create a custom widget that can
+both display its own content and respond to user input.
+
+The example displays an array of characters which the user can click on
+to enter text in a line edit. The contents of the line edit can then be
+copied into the clipboard, and pasted into other applications. The
+purpose behind this sort of tool is to allow users to enter characters
+that may be unavailable or difficult to locate on their keyboards.
+
+\image charactermap-example.png Screenshot of the Character Map example
+
+The example consists of the following classes:
+
+\list
+\i \c CharacterWidget displays the available characters in the current
+   font and style.
+\i \c MainWindow provides a standard main window that contains font and
+   style information, a view onto the characters, a line edit, and a push
+   button for submitting text to the clipboard.
+\endlist
+
+\section1 CharacterWidget Class Definition
+
+The \c CharacterWidget class is used to display an array of characters in
+a user-specified font and style. For flexibility, we subclass QWidget and
+reimplement only the functions that we need to provide basic rendering
+and interaction features.
+
+The class definition looks like this:
+
+\snippet examples/widgets/charactermap/characterwidget.h 0
+
+The widget does not contain any other widgets, so it must provide its own
+size hint to allow its contents to be displayed correctly.
+We reimplement \l{QWidget::paintEvent()} to draw custom content. We also
+reimplement \l{QWidget::mousePressEvent()} to allow the user to interact
+with the widget.
+
+The updateFont() and updateStyle() slots are used to update the font and
+style of the characters in the widget whenever the user changes the
+settings in the application.
+The class defines the characterSelected() signal so that other parts
+of the application are informed whenever the user selects a character in
+the widget.
+As a courtesy, the widget provides a tooltip that shows the current
+character value. We reimplement the \l{QWidget::mouseMoveEvent()} event
+handler and define showToolTip() to enable this feature.
+
+The \c columns, \c displayFont and \c currentKey private data members
+are used to record the number of columns to be shown, the current font,
+and the currently highlighted character in the widget.
+
+\section1 CharacterWidget Class Implementation
+
+Since the widget is to be used as a simple canvas, the constructor just
+calls the base class constructor and defines some default values for
+private data members.
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 0
+
+We initialize \c currentKey with a value of -1 to indicate
+that no character is initially selected. We enable mouse tracking to
+allow us to follow the movement of the cursor across the widget.
+
+The class provides two functions to allow the font and style to be set up.
+Each of these modify the widget's display font and call update():
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 1
+\codeline
+\snippet examples/widgets/charactermap/characterwidget.cpp 2
+
+We use a fixed size font for the display. Similarly, a fixed size hint is
+provided by the sizeHint() function:
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 3
+
+Three standard event functions are implemented so that the widget
+can respond to clicks, provide tooltips, and render the available
+characters. The paintEvent() shows how the contents of the widget are
+arranged and displayed:
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 6
+
+A QPainter is created for the widget and, in all cases, we ensure that the
+widget's background is painted. The painter's font is set to the
+user-specified display font.
+
+The area of the widget that needs to be redrawn is used to determine which
+characters need to be displayed:
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 7
+
+Using integer division, we obtain the row and column numbers of each
+characters that should be displayed, and we draw a square on the widget
+for each character displayed.
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 8
+\snippet examples/widgets/charactermap/characterwidget.cpp 9
+
+The symbols for each character in the array are drawn within each square,
+with the symbol for the most recently selected character displayed in red:
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 10
+
+We do not need to take into account the difference between the area
+displayed in the viewport and the area we are drawing on because
+everything outside the visible area will be clipped.
+
+The mousePressEvent() defines how the widget responds to mouse clicks.
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 5
+
+We are only interested when the user clicks with the left mouse button
+over the widget. When this happens, we calculate which character was
+selected and emit the characterSelected() signal.
+The character's number is found by dividing the x and y-coordinates of
+the click by the size of each character's grid square. Since the number
+of columns in the widget is defined by the \c columns variable, we
+simply multiply the row index by that value and add the column number
+to obtain the character number.
+
+If any other mouse button is pressed, the event is passed on to the
+QWidget base class. This ensures that the event can be handled properly
+by any other interested widgets.
+
+The mouseMoveEvent() maps the mouse cursor's position in global
+coordinates to widget coordinates, and determines the character that
+was clicked by performing the calculation
+
+\snippet examples/widgets/charactermap/characterwidget.cpp 4
+
+The tooltip is given a position defined in global coordinates.
+
+\section1 MainWindow Class Definition
+
+The \c MainWindow class provides a minimal user interface for the example,
+with only a constructor, slots that respond to signals emitted by standard
+widgets, and some convenience functions that are used to set up the user
+interface.
+
+The class definition looks like this:
+
+\snippet examples/widgets/charactermap/mainwindow.h 0
+
+The main window contains various widgets that are used to control how
+the characters will be displayed, and defines the findFonts() function
+for clarity and convenience. The findStyles() slot is used by the widgets
+to determine the styles that are available, insertCharacter() inserts
+a user-selected character into the window's line edit, and
+updateClipboard() synchronizes the clipboard with the contents of the
+line edit.
+
+\section1 MainWindow Class Implementation
+
+In the constructor, we set up the window's central widget and fill it with
+some standard widgets (two comboboxes, a line edit, and a push button).
+We also construct a CharacterWidget custom widget, and add a QScrollArea
+so that we can view its contents:
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 0
+
+QScrollArea provides a viewport onto the \c CharacterWidget when we set
+its widget and handles much of the work needed to provide a scrolling
+viewport.
+
+The font combo box is automatically popuplated with a list of available
+fonts. We list the available styles for the current font in the style
+combobox using the following function:
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 1
+
+The line edit and push button are used to supply text to the clipboard:
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 2
+
+We also obtain a clipboard object so that we can send text entered by the
+user to other applications.
+
+Most of the signals emitted in the example come from standard widgets.
+We connect these signals to slots in this class, and to the slots provided
+by other widgets.
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 4
+
+The font combobox's
+\l{QFontComboBox::currentFontChanged()}{currentFontChanged()} signal is
+connected to the findStyles() function so that the list of available styles
+can be shown for each font that is used. Since both the font and the style
+can be changed by the user, the font combobox's currentFontChanged() signal
+and the style combobox's
+\l{QComboBox::currentIndexChanged()}{currentIndexChanged()} are connected
+directly to the character widget.
+
+The final two connections allow characters to be selected in the character
+widget, and text to be inserted into the clipboard:
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 5
+
+The character widget emits the characterSelected() custom signal when
+the user clicks on a character, and this is handled by the insertCharacter()
+function in this class. The clipboard is changed when the push button emits
+the clicked() signal, and we handle this with the updateClipboard() function.
+
+The remaining code in the constructor sets up the layout of the central widget,
+and provides a window title:
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 6
+
+The font combobox is automatically populated with a list of available font
+families. The styles that can be used with each font are found by the
+findStyles() function. This function is called whenever the user selects a
+different font in the font combobox.
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 7
+
+We begin by recording the currently selected style, and we clear the
+style combobox so that we can insert the styles associated with the
+current font family.
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 8
+
+We use the font database to collect the styles that are available for the
+current font, and insert them into the style combobox. The current item is
+reset if the original style is not available for this font.
+
+The last two functions are slots that respond to signals from the character
+widget and the main window's push button. The insertCharacter() function is
+used to insert characters from the character widget when the user clicks a
+character:
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 9
+
+The character is inserted into the line edit at the current cursor position.
+
+The main window's "To clipboard" push button is connected to the
+updateClipboard() function so that, when it is clicked, the clipboard is
+updated to contain the contents of the line edit:
+
+\snippet examples/widgets/charactermap/mainwindow.cpp 10
+
+We copy all the text from the line edit to the clipboard, but we do not clear
+the line edit.
+*/