source: trunk/src/gui/kernel/qwhatsthis.cpp@ 846

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#include "qwhatsthis.h"
#ifndef QT_NO_WHATSTHIS
#include "qpointer.h"
#include "qapplication.h"
#include "qdesktopwidget.h"
#include "qevent.h"
#include "qpixmap.h"
#include "qpainter.h"
#include "qtimer.h"
#include "qhash.h"
#include "qaction.h"
#include "qcursor.h"
#include "qbitmap.h"
#include "qtextdocument.h"
#include "../text/qtextdocumentlayout_p.h"
#include "qtoolbutton.h"
#include "qdebug.h"
#ifndef QT_NO_ACCESSIBILITY
#include "qaccessible.h"
#endif
#if defined(Q_WS_WIN)
#include "qt_windows.h"
#ifndef SPI_GETDROPSHADOW
#define SPI_GETDROPSHADOW                   0x1024
#endif
#endif
#if defined(Q_WS_X11)
#include "qx11info_x11.h"
#include <qwidget.h>
#endif

QT_BEGIN_NAMESPACE

/*!
    \class QWhatsThis
    \brief The QWhatsThis class provides a simple description of any
    widget, i.e. answering the question "What's This?".

    \ingroup helpsystem


    "What's This?" help is part of an application's online help
    system, and provides users with information about the
    functionality and usage of a particular widget. "What's This?"
    help texts are typically longer and more detailed than \link
    QToolTip tooltips\endlink, but generally provide less information
    than that supplied by separate help windows.

    QWhatsThis provides a single window with an explanatory text that
    pops up when the user asks "What's This?". The default way for
    users to ask the question is to move the focus to the relevant
    widget and press Shift+F1. The help text appears immediately; it
    goes away as soon as the user does something else.
    (Note that if there is a shortcut for Shift+F1, this mechanism
    will not work.) Some dialogs provide a "?" button that users can
    click to enter "What's This?" mode; they then click the relevant
    widget to pop up the "What's This?" window. It is also possible to
    provide a a menu option or toolbar button to switch into "What's
    This?" mode.

    To add "What's This?" text to a widget or an action, you simply
    call QWidget::setWhatsThis() or QAction::setWhatsThis().

    The text can be either rich text or plain text. If you specify a
    rich text formatted string, it will be rendered using the default
    stylesheet, making it possible to embed images in the displayed
    text. To be as fast as possible, the default stylesheet uses a
    simple method to determine whether the text can be rendered as
    plain text. See Qt::mightBeRichText() for details.

    \snippet doc/src/snippets/whatsthis/whatsthis.cpp 0

    An alternative way to enter "What's This?" mode is to call
    createAction(), and add the returned QAction to either a menu or
    a tool bar. By invoking this context help action (in the picture
    below, the button with the arrow and question mark icon) the user
    switches into "What's This?" mode. If they now click on a widget
    the appropriate help text is shown. The mode is left when help is
    given or when the user presses Esc.

    \img whatsthis.png

    You can enter "What's This?" mode programmatically with
    enterWhatsThisMode(), check the mode with inWhatsThisMode(), and
    return to normal mode with leaveWhatsThisMode().

    If you want to control the "What's This?" behavior of a widget
    manually see Qt::WA_CustomWhatsThis.

    It is also possible to show different help texts for different
    regions of a widget, by using a QHelpEvent of type
    QEvent::WhatsThis. Intercept the help event in your widget's
    QWidget::event() function and call QWhatsThis::showText() with the
    text you want to display for the position specified in
    QHelpEvent::pos(). If the text is rich text and the user clicks
    on a link, the widget also receives a QWhatsThisClickedEvent with
    the link's reference as QWhatsThisClickedEvent::href(). If a
    QWhatsThisClickedEvent is handled (i.e. QWidget::event() returns
    true), the help window remains visible. Call
    QWhatsThis::hideText() to hide it explicitly.

    \sa QToolTip
*/

Q_CORE_EXPORT void qDeleteInEventHandler(QObject *o);

class QWhatsThat : public QWidget
{
    Q_OBJECT

public:
    QWhatsThat(const QString& txt, QWidget* parent, QWidget *showTextFor);
    ~QWhatsThat() ;

    static QWhatsThat *instance;

protected:
    void showEvent(QShowEvent *e);
    void mousePressEvent(QMouseEvent*);
    void mouseReleaseEvent(QMouseEvent*);
    void mouseMoveEvent(QMouseEvent*);
    void keyPressEvent(QKeyEvent*);
    void paintEvent(QPaintEvent*);

private:
    QPointer<QWidget>widget;
    bool pressed;
    QString text;
    QTextDocument* doc;
    QString anchor;
    QPixmap background;
};

QWhatsThat *QWhatsThat::instance = 0;

// shadowWidth not const, for XP drop-shadow-fu turns it to 0
static int shadowWidth = 6;   // also used as '5' and '6' and even '8' below
static const int vMargin = 8;
static const int hMargin = 12;

QWhatsThat::QWhatsThat(const QString& txt, QWidget* parent, QWidget *showTextFor)
    : QWidget(parent, Qt::Popup),
      widget(showTextFor), pressed(false), text(txt)
{
    delete instance;
    instance = this;