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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.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** No Commercial Usage
+** This file contains pre-release code and may not be distributed.
+** You may use this file in accordance with the terms and conditions
+** contained in the either Technology Preview License Agreement or the
+** Beta Release License Agreement.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU Lesser General Public License version 2.1 requirements
+** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Nokia gives you certain
+** additional rights. These rights are described in the Nokia Qt LGPL
+** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
+** package.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3.0 as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL included in the
+** packaging of this file.  Please review the following information to
+** ensure the GNU General Public License version 3.0 requirements will be
+** met: http://www.gnu.org/copyleft/gpl.html.
+**
+** If you are unsure which license is appropriate for your use, please
+** contact the sales department at qt-sales@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/****************************************************************************
+**
+** Documentation of focus handling in Qt.
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** Contact: Qt Software Information (qt-info@nokia.com)
+**
+** This file is part of the Qt GUI Toolkit.
+** EDITIONS: FREE, PROFESSIONAL, ENTERPRISE
+**
+****************************************************************************/
+
+/*!
+    \page focus.html
+    \title Keyboard Focus
+    \ingroup architecture
+    \ingroup gui-programming
+    \brief An overview of the keyboard focus management and handling.
+
+    \keyword keyboard focus
+
+    Qt's widgets handle keyboard focus in the ways that have become
+    customary in GUIs. 
+
+    The basic issue is that the user's key strokes can be directed at any
+    of several windows on the screen, and any of several widgets inside
+    the intended window. When the user presses a key, they expect it to go
+    to the right place, and the software must try to meet this
+    expectation. The system must determine which application the key stroke
+    is directed at, which window within that application, and which widget
+    within that window.
+
+    \section1 Focus Motion
+
+    The customs which have evolved for directing keyboard focus to a
+    particular widget are these: 
+
+    \list 1
+
+    \o The user presses \key Tab (or \key Shift+Tab).
+    \o The user clicks a widget.
+    \o The user presses a keyboard shortcut.
+    \o The user uses the mouse wheel.
+    \o The user moves the focus to a window, and the application must
+       determine which widget within the window should get the focus.
+    \endlist
+
+    Each of these motion mechanisms is different, and different types of
+    widgets receive focus in only some of them. We'll cover each of them
+    in turn.
+
+    \section2 Tab or Shift+Tab
+
+    Pressing \key Tab is by far the most common way to move focus
+    using the keyboard. (Sometimes in data-entry applications Enter
+    does the same as \key{Tab}; this can easily be achieved in Qt by
+    implementing an \l{Events and Event Filters}{event filter}.)
+
+    Pressing \key Tab, in all window systems in common use today,
+    moves the keyboard focus to the next widget in a circular
+    per-window list. \key Tab moves focus along the circular list in
+    one direction, \key Shift+Tab in the other. The order in which
+    \key Tab presses move from widget to widget is called the tab order.
+
+    You can customize the tab order using QWidget::setTabOrder(). (If
+    you don't, \key Tab generally moves focus in the order of widget
+    construction.) \l{Qt Designer} provides a means of visually
+    changing the tab order.
+
+    Since pressing \key Tab is so common, most widgets that can have focus
+    should support tab focus. The major exception is widgets that are
+    rarely used, and where there is some keyboard accelerator or error
+    handler that moves the focus.
+
+    For example, in a data entry dialog, there might be a field that
+    is only necessary in one per cent of all cases. In such a dialog,
+    \key Tab could skip this field, and the dialog could use one of
+    these mechanisms: 
+
+    \list 1
+
+    \o If the program can determine whether the field is needed, it can
+    move focus there when the user finishes entry and presses \gui OK, or when
+    the user presses Enter after finishing the other fields. Alternately,
+    include the field in the tab order but disable it. Enable it if it
+    becomes appropriate in view of what the user has set in the other
+    fields.
+
+    \o The label for the field can include a keyboard shortcut that moves
+    focus to this field.
+
+    \endlist
+
+    Another exception to \key Tab support is text-entry widgets that
+    must support the insertion of tabs; almost all text editors fall
+    into this class. Qt treats \key Ctrl+Tab as \key Tab and \key
+    Ctrl+Shift+Tab as \key Shift+Tab, and such widgets can
+    reimplement QWidget::event() and handle Tab before calling
+    QWidget::event() to get normal processing of all other keys.
+    However, since some systems use \key Ctrl+Tab for other purposes,
+    and many users aren't aware of \key Ctrl+Tab anyway, this isn't a
+    complete solution.
+
+    \section2 The User Clicks a Widget
+
+    This is perhaps even more common than pressing \key Tab on
+    computers with a mouse or other pointing device.
+
+    Clicking to move the focus is slightly more powerful than \key
+    Tab. While it moves the focus \e to a widget, for editor widgets
+    it also moves the text cursor (the widget's internal focus) to
+    the spot where the mouse is clicked.
+
+    Since it is so common and people are used to it, it's a good idea to
+    support it for most widgets. However, there is also an important
+    reason to avoid it: you may not want to remove focus from the widget
+    where it was.
+
+    For example, in a word processor, when the user clicks the 'B' (bold)
+    tool button, what should happen to the keyboard focus? Should it
+    remain where it was, almost certainly in the editing widget, or should
+    it move to the 'B' button?
+
+    We advise supporting click-to-focus for widgets that support text
+    entry, and to avoid it for most widgets where a mouse click has a
+    different effect. (For buttons, we also recommend adding a keyboard
+    shortcut: QAbstractButton and its subclasses make this very easy.)
+
+    In Qt, only the QWidget::setFocusPolicy() function affects
+    click-to-focus.
+
+    \section2 The User Presses a Keyboard Shortcut
+
+    It's not unusual for keyboard shortcuts to move the focus. This
+    can happen implicitly by opening modal dialogs, but also
+    explicitly using focus accelerators such as those provided by
+    QLabel::setBuddy(), QGroupBox, and QTabBar.
+
+    We advise supporting shortcut focus for all widgets that the user
+    may want to jump to. For example, a tab dialog can have keyboard
+    shortcuts for each of its pages, so the user can press e.g. \key
+    Alt+P to step to the \underline{P}rinting page. It is easy to
+    overdo this: there are only a few keys, and it's also important
+    to provide keyboard shortcuts for commands. \key Alt+P is also
+    used for Paste, Play, Print, and Print Here in the \l{Standard
+    Accelerator Keys} list, for example.
+
+    \section2 The User Rotates the Mouse Wheel
+
+    On Microsoft Windows, mouse wheel usage is always handled by the
+    widget that has keyboard focus. On Mac OS X and X11, it's handled by
+    the widget that gets other mouse events.
+
+    The way Qt handles this platform difference is by letting widgets move
+    the keyboard focus when the wheel is used. With the right focus policy
+    on each widget, applications can work idiomatically correctly on
+    Windows, Mac OS X, and X11.
+
+    \section2 The User Moves the Focus to This Window
+
+    In this situation the application must determine which widget within
+    the window should receive the focus.
+
+    This can be simple: If the focus has been in this window before,
+    then the last widget to have focus should regain it. Qt does this
+    automatically.
+
+    If focus has never been in this window before and you know where
+    focus should start out, call QWidget::setFocus() on the widget
+    which should receive focus before you call QWidget::show() it. If
+    you don't, Qt will pick a suitable widget.
+*/