qt-everywhere-src-5.15.1/qtbase/src/widgets/kernel/qwhatsthis.cpp - orbit - Git at Google

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 #include "qwhatsthis.h"
 #include "qpointer.h"
 #include "qapplication.h"
 #include <private/qguiapplication_p.h>
 #include "qdesktopwidget.h"
 #include <private/qdesktopwidget_p.h>
 #include "qevent.h"
 #include "qpixmap.h"
 #include "qscreen.h"
 #include "qpainter.h"
 #include "qtimer.h"
 #if QT_CONFIG(action)
 #include "qaction.h"
 #endif // QT_CONFIG(action)
 #include "qcursor.h"
 #include "qbitmap.h"
 #include "qtextdocument.h"
 #include <qpa/qplatformtheme.h>
 #include "private/qtextdocumentlayout_p.h"
 #include "qdebug.h"
 #ifndef QT_NO_ACCESSIBILITY
 #include "qaccessible.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
     \inmodule QtWidgets

     "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
     \l{QToolTip}{tooltips}, 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 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.

     \image 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) override;
     void mousePressEvent(QMouseEvent*) override;
     void mouseReleaseEvent(QMouseEvent*) override;
     void mouseMoveEvent(QMouseEvent*) override;
     void keyPressEvent(QKeyEvent*) override;
     void paintEvent(QPaintEvent*) override;

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

 QWhatsThat *QWhatsThat::instance = nullptr;

 // 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;

 static inline bool dropShadow()
 {
     if (const QPlatformTheme *theme = QGuiApplicationPrivate::platformTheme())
         return theme->themeHint(QPlatformTheme::DropShadow).toBool();
     return false;
 }

 QWhatsThat::QWhatsThat(const QString& txt, QWidget* parent, QWidget *showTextFor)
     : QWidget(parent, Qt::Popup),
       widget(showTextFor), pressed(false), text(txt)
 {
     delete instance;
     instance = this;
     setAttribute(Qt::WA_DeleteOnClose, true);
     setAttribute(Qt::WA_NoSystemBackground, true);
     if (parent)
         setPalette(parent->palette());
     setMouseTracking(true);
     setFocusPolicy(Qt::StrongFocus);
 #ifndef QT_NO_CURSOR
     setCursor(Qt::ArrowCursor);
 #endif
     QRect r;
     doc = nullptr;
     ensurePolished(); // Ensures style sheet font before size calc
     if (Qt::mightBeRichText(text)) {
         doc = new QTextDocument();
         doc->setUndoRedoEnabled(false);
         doc->setDefaultFont(QApplication::font(this));
 #ifdef QT_NO_TEXTHTMLPARSER
         doc->setPlainText(text);
 #else
         doc->setHtml(text);
 #endif
         doc->setUndoRedoEnabled(false);
         doc->adjustSize();
         r.setTop(0);
         r.setLeft(0);
         r.setSize(doc->size().toSize());
     }
     else
     {
         int sw = QDesktopWidgetPrivate::width() / 3;
         if (sw < 200)
             sw = 200;
         else if (sw > 300)
             sw = 300;

         r = fontMetrics().boundingRect(0, 0, sw, 1000,
                                         Qt::AlignLeft + Qt::AlignTop
                                         + Qt::TextWordWrap + Qt::TextExpandTabs,
                                         text);
     }
     shadowWidth = dropShadow() ? 0 : 6;
     resize(r.width() + 2*hMargin + shadowWidth, r.height() + 2*vMargin + shadowWidth);
 }

 QWhatsThat::~QWhatsThat()
 {
     instance = nullptr;
     if (doc)
         delete doc;
 }

 void QWhatsThat::showEvent(QShowEvent *)
 {
     background = QGuiApplication::primaryScreen()->grabWindow(QApplication::desktop()->internalWinId(),
                                                               x(), y(), width(), height());
 }

 void QWhatsThat::mousePressEvent(QMouseEvent* e)
 {
     pressed = true;
     if (e->button() == Qt::LeftButton && rect().contains(e->pos())) {
         if (doc)
             anchor = doc->documentLayout()->anchorAt(e->pos() -  QPoint(hMargin, vMargin));
         return;
     }
     close();
 }

 void QWhatsThat::mouseReleaseEvent(QMouseEvent* e)
 {
     if (!pressed)
         return;
     if (widget && e->button() == Qt::LeftButton && doc && rect().contains(e->pos())) {
         QString a = doc->documentLayout()->anchorAt(e->pos() -  QPoint(hMargin, vMargin));
         QString href;
         if (anchor == a)
             href = a;
         anchor.clear();
         if (!href.isEmpty()) {
             QWhatsThisClickedEvent e(href);
             if (QCoreApplication::sendEvent(widget, &e))
                 return;
         }
     }
     close();
 }

 void QWhatsThat::mouseMoveEvent(QMouseEvent* e)
 {
 #ifdef QT_NO_CURSOR
     Q_UNUSED(e);
 #else
     if (!doc)
         return;
     QString a = doc->documentLayout()->anchorAt(e->pos() -  QPoint(hMargin, vMargin));
     if (!a.isEmpty())
         setCursor(Qt::PointingHandCursor);
     else
         setCursor(Qt::ArrowCursor);
 #endif
 }

 void QWhatsThat::keyPressEvent(QKeyEvent*)
 {
     close();
 }

 void QWhatsThat::paintEvent(QPaintEvent*)
 {
     const bool drawShadow = dropShadow();

     QRect r = rect();
     r.adjust(0, 0, -1, -1);
     if (drawShadow)
         r.adjust(0, 0, -shadowWidth, -shadowWidth);
     QPainter p(this);
     p.drawPixmap(0, 0, background);
     p.setPen(QPen(palette().toolTipText(), 0));
     p.setBrush(palette().toolTipBase());
     p.drawRect(r);
     int w = r.width();
     int h = r.height();
     p.setPen(palette().brush(QPalette::Dark).color());
     p.drawRect(1, 1, w-2, h-2);
     if (drawShadow) {
         p.setPen(palette().shadow().color());
         p.drawPoint(w + 5, 6);
         p.drawLine(w + 3, 6, w + 5, 8);
         p.drawLine(w + 1, 6, w + 5, 10);
         int i;
         for(i=7; i < h; i += 2)
             p.drawLine(w, i, w + 5, i + 5);
         for(i = w - i + h; i > 6; i -= 2)
             p.drawLine(i, h, i + 5, h + 5);
         for(; i > 0 ; i -= 2)
             p.drawLine(6, h + 6 - i, i + 5, h + 5);
     }
     r.adjust(0, 0, 1, 1);
     p.setPen(palette().toolTipText().color());
     r.adjust(hMargin, vMargin, -hMargin, -vMargin);

     if (doc) {
         p.translate(r.x(), r.y());
         QRect rect = r;
         rect.translate(-r.x(), -r.y());
         p.setClipRect(rect);
         QAbstractTextDocumentLayout::PaintContext context;
         context.palette.setBrush(QPalette::Text, context.palette.toolTipText());
         doc->documentLayout()->draw(&p, context);
     }
     else
     {
         p.drawText(r, Qt::AlignLeft + Qt::AlignTop + Qt::TextWordWrap + Qt::TextExpandTabs, text);
     }
 }

 static const char * const button_image[] = {
 "16 16 3 1",
 "         c None",
 "o        c #000000",
 "a        c #000080",
 "o        aaaaa  ",
 "oo      aaa aaa ",
 "ooo    aaa   aaa",
 "oooo   aa     aa",
 "ooooo  aa     aa",
 "oooooo  a    aaa",
 "ooooooo     aaa ",
 "oooooooo   aaa  ",
 "ooooooooo aaa   ",
 "ooooo     aaa   ",
 "oo ooo          ",
 "o  ooo    aaa   ",
 "    ooo   aaa   ",
 "    ooo         ",
 "     ooo        ",
 "     ooo        "};

 class QWhatsThisPrivate : public QObject
 {
  public:
     QWhatsThisPrivate();
     ~QWhatsThisPrivate();
     static QWhatsThisPrivate *instance;
     bool eventFilter(QObject *, QEvent *) override;
 #if QT_CONFIG(action)
     QPointer<QAction> action;
 #endif // QT_CONFIG(action)
     static void say(QWidget *, const QString &, int x = 0, int y = 0);
     static void notifyToplevels(QEvent *e);
     bool leaveOnMouseRelease;
 };

 void QWhatsThisPrivate::notifyToplevels(QEvent *e)
 {
     const QWidgetList toplevels = QApplication::topLevelWidgets();
     for (auto *w : toplevels)
         QCoreApplication::sendEvent(w, e);
 }

 QWhatsThisPrivate *QWhatsThisPrivate::instance = nullptr;

 QWhatsThisPrivate::QWhatsThisPrivate()
     : leaveOnMouseRelease(false)
 {
     instance = this;
     qApp->installEventFilter(this);

     QPoint pos = QCursor::pos();
     if (QWidget *w = QApplication::widgetAt(pos)) {
         QHelpEvent e(QEvent::QueryWhatsThis, w->mapFromGlobal(pos), pos);
         const bool sentEvent = QCoreApplication::sendEvent(w, &e);
 #ifdef QT_NO_CURSOR
         Q_UNUSED(sentEvent);
 #else
         QGuiApplication::setOverrideCursor((!sentEvent || !e.isAccepted())?
                                         Qt::ForbiddenCursor:Qt::WhatsThisCursor);
     } else {
         QGuiApplication::setOverrideCursor(Qt::WhatsThisCursor);
 #endif
     }
 #ifndef QT_NO_ACCESSIBILITY
     QAccessibleEvent event(this, QAccessible::ContextHelpStart);
     QAccessible::updateAccessibility(&event);
 #endif
 }

 QWhatsThisPrivate::~QWhatsThisPrivate()
 {
 #if QT_CONFIG(action)
     if (action)
         action->setChecked(false);
 #endif // QT_CONFIG(action)
 #ifndef QT_NO_CURSOR
     QGuiApplication::restoreOverrideCursor();
 #endif
 #ifndef QT_NO_ACCESSIBILITY
     QAccessibleEvent event(this, QAccessible::ContextHelpEnd);
     QAccessible::updateAccessibility(&event);
 #endif
     instance = nullptr;
 }

 bool QWhatsThisPrivate::eventFilter(QObject *o, QEvent *e)
 {
     if (!o->isWidgetType())
         return false;
     QWidget * w = static_cast<QWidget *>(o);
     bool customWhatsThis = w->testAttribute(Qt::WA_CustomWhatsThis);
     switch (e->type()) {
     case QEvent::MouseButtonPress:
     {
         QMouseEvent *me = static_cast<QMouseEvent*>(e);
         if (me->button() == Qt::RightButton || customWhatsThis)
             return false;
         QHelpEvent e(QEvent::WhatsThis, me->pos(), me->globalPos());
         if (!QCoreApplication::sendEvent(w, &e) || !e.isAccepted())
             leaveOnMouseRelease = true;

     } break;

     case QEvent::MouseMove:
     {
         QMouseEvent *me = static_cast<QMouseEvent*>(e);
         QHelpEvent e(QEvent::QueryWhatsThis, me->pos(), me->globalPos());
         const bool sentEvent = QCoreApplication::sendEvent(w, &e);
 #ifdef QT_NO_CURSOR
         Q_UNUSED(sentEvent);
 #else
         QGuiApplication::changeOverrideCursor((!sentEvent || !e.isAccepted())?
                                               Qt::ForbiddenCursor:Qt::WhatsThisCursor);
 #endif
         Q_FALLTHROUGH();
     }
     case QEvent::MouseButtonRelease:
     case QEvent::MouseButtonDblClick:
         if (leaveOnMouseRelease && e->type() == QEvent::MouseButtonRelease)
             QWhatsThis::leaveWhatsThisMode();
         if (static_cast<QMouseEvent*>(e)->button() == Qt::RightButton || customWhatsThis)
             return false; // ignore RMB release
         break;
     case QEvent::KeyPress:
     {
         QKeyEvent* kev = (QKeyEvent*)e;
 #if QT_CONFIG(shortcut)
         if (kev->matches(QKeySequence::Cancel)) {
             QWhatsThis::leaveWhatsThisMode();
             return true;
         } else
 #endif
           if (customWhatsThis) {
             return false;
         } else if (kev->key() == Qt::Key_Menu ||
                     (kev->key() == Qt::Key_F10 &&
                       kev->modifiers() == Qt::ShiftModifier)) {
             // we don't react to these keys, they are used for context menus
             return false;
         } else if (kev->key() != Qt::Key_Shift && kev->key() != Qt::Key_Alt // not a modifier key
                    && kev->key() != Qt::Key_Control && kev->key() != Qt::Key_Meta) {
             QWhatsThis::leaveWhatsThisMode();
         }
     } break;
     default:
         return false;
     }
     return true;
 }

 #if QT_CONFIG(action)
 class QWhatsThisAction: public QAction
 {
     Q_OBJECT

 public:
     explicit QWhatsThisAction(QObject* parent = nullptr);

 private slots:
     void actionTriggered();
 };

 QWhatsThisAction::QWhatsThisAction(QObject *parent) : QAction(tr("What's This?"), parent)
 {
 #ifndef QT_NO_IMAGEFORMAT_XPM
     QPixmap p(button_image);
     setIcon(p);
 #endif
     setCheckable(true);
     connect(this, SIGNAL(triggered()), this, SLOT(actionTriggered()));
 #ifndef QT_NO_SHORTCUT
     setShortcut(Qt::ShiftModifier + Qt::Key_F1);
 #endif
 }

 void QWhatsThisAction::actionTriggered()
 {
     if (isChecked()) {
         QWhatsThis::enterWhatsThisMode();
         QWhatsThisPrivate::instance->action = this;
     }
 }
 #endif // QT_CONFIG(action)

 /*!
     This function switches the user interface into "What's This?"
     mode. The user interface can be switched back into normal mode by
     the user (e.g. by them clicking or pressing Esc), or
     programmatically by calling leaveWhatsThisMode().

     When entering "What's This?" mode, a QEvent of type
     Qt::EnterWhatsThisMode is sent to all toplevel widgets.

     \sa inWhatsThisMode(), leaveWhatsThisMode()
 */
 void QWhatsThis::enterWhatsThisMode()
 {
     if (QWhatsThisPrivate::instance)
         return;
     (void) new QWhatsThisPrivate;
     QEvent e(QEvent::EnterWhatsThisMode);
     QWhatsThisPrivate::notifyToplevels(&e);
  }

 /*!
     Returns \c true if the user interface is in "What's This?" mode;
     otherwise returns \c false.

     \sa enterWhatsThisMode()
 */
 bool QWhatsThis::inWhatsThisMode()
 {
     return (QWhatsThisPrivate::instance != nullptr);
 }

 /*!
     If the user interface is in "What's This?" mode, this function
     switches back to normal mode; otherwise it does nothing.

     When leaving "What's This?" mode, a QEvent of type
     Qt::LeaveWhatsThisMode is sent to all toplevel widgets.

     \sa enterWhatsThisMode(), inWhatsThisMode()
 */
 void QWhatsThis::leaveWhatsThisMode()
 {
     delete QWhatsThisPrivate::instance;
     QEvent e(QEvent::LeaveWhatsThisMode);
     QWhatsThisPrivate::notifyToplevels(&e);
 }

 void QWhatsThisPrivate::say(QWidget * widget, const QString &text, int x, int y)
 {
     if (text.size() == 0)
         return;
     // make a fresh widget, and set it up
     QWhatsThat *whatsThat = new QWhatsThat(text, nullptr, widget);

     // okay, now to find a suitable location
     int scr = (widget ?
                 QDesktopWidgetPrivate::screenNumber(widget) :
                 QDesktopWidgetPrivate::screenNumber(QPoint(x,y))
                );
     QRect screen = QDesktopWidgetPrivate::screenGeometry(scr);

     int w = whatsThat->width();
     int h = whatsThat->height();
     int sx = screen.x();
     int sy = screen.y();

     // first try locating the widget immediately above/below,
     // with nice alignment if possible.
     QPoint pos;
     if (widget)
         pos = widget->mapToGlobal(QPoint(0,0));

     if (widget && w > widget->width() + 16)
         x = pos.x() + widget->width()/2 - w/2;
     else
         x = x - w/2;

         // squeeze it in if that would result in part of what's this
         // being only partially visible
     if (x + w  + shadowWidth > sx+screen.width())
         x = (widget? (qMin(screen.width(),
                            pos.x() + widget->width())
                      ) : screen.width())
             - w;

     if (x < sx)
         x = sx;

     if (widget && h > widget->height() + 16) {
         y = pos.y() + widget->height() + 2; // below, two pixels spacing
         // what's this is above or below, wherever there's most space
         if (y + h + 10 > sy+screen.height())
             y = pos.y() + 2 - shadowWidth - h; // above, overlap
     }
     y = y + 2;

         // squeeze it in if that would result in part of what's this
         // being only partially visible
     if (y + h + shadowWidth > sy+screen.height())
         y = (widget ? (qMin(screen.height(),
                              pos.y() + widget->height())
                        ) : screen.height())
             - h;
     if (y < sy)
         y = sy;

     whatsThat->move(x, y);
     whatsThat->show();
     whatsThat->grabKeyboard();
 }

 /*!
     Shows \a text as a "What's This?" window, at global position \a
     pos. The optional widget argument, \a w, is used to determine the
     appropriate screen on multi-head systems.

     \sa hideText()
 */
 void QWhatsThis::showText(const QPoint &pos, const QString &text, QWidget *w)
 {
     leaveWhatsThisMode();
     QWhatsThisPrivate::say(w, text, pos.x(), pos.y());
 }

 /*!
     If a "What's This?" window is showing, this destroys it.

     \sa showText()
 */
 void QWhatsThis::hideText()
 {
     qDeleteInEventHandler(QWhatsThat::instance);
 }

 /*!
     Returns a ready-made QAction, used to invoke "What's This?" context
     help, with the given \a parent.

     The returned QAction provides a convenient way to let users enter
     "What's This?" mode.
 */
 #if QT_CONFIG(action)
 QAction *QWhatsThis::createAction(QObject *parent)
 {
     return new QWhatsThisAction(parent);
 }
 #endif // QT_CONFIG(action)

 QT_END_NAMESPACE

 #include "qwhatsthis.moc"
	/****************************************************************************
	**
	** Copyright (C) 2016 The Qt Company Ltd.
	** Contact: https://www.qt.io/licensing/
	**
	** This file is part of the QtWidgets module of the Qt Toolkit.
	**
	** $QT_BEGIN_LICENSE:LGPL$
	** Commercial License Usage
	** Licensees holding valid commercial Qt licenses may use this file in
	** accordance with the commercial license agreement provided with the
	** Software or, alternatively, in accordance with the terms contained in
	** a written agreement between you and The Qt Company. For licensing terms
	** and conditions see https://www.qt.io/terms-conditions. For further
	** information use the contact form at https://www.qt.io/contact-us.
	**
	** GNU Lesser General Public License Usage
	** Alternatively, this file may be used under the terms of the GNU Lesser
	** General Public License version 3 as published by the Free Software
	** Foundation and appearing in the file LICENSE.LGPL3 included in the
	** packaging of this file. Please review the following information to
	** ensure the GNU Lesser General Public License version 3 requirements
	** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
	**
	** GNU General Public License Usage
	** Alternatively, this file may be used under the terms of the GNU
	** General Public License version 2.0 or (at your option) the GNU General
	** Public license version 3 or any later version approved by the KDE Free
	** Qt Foundation. The licenses are as published by the Free Software
	** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
	** included in the packaging of this file. Please review the following
	** information to ensure the GNU General Public License requirements will
	** be met: https://www.gnu.org/licenses/gpl-2.0.html and
	** https://www.gnu.org/licenses/gpl-3.0.html.
	**
	** $QT_END_LICENSE$
	**
	****************************************************************************/

	#include "qwhatsthis.h"
	#include "qpointer.h"
	#include "qapplication.h"
	#include <private/qguiapplication_p.h>
	#include "qdesktopwidget.h"
	#include <private/qdesktopwidget_p.h>
	#include "qevent.h"
	#include "qpixmap.h"
	#include "qscreen.h"
	#include "qpainter.h"
	#include "qtimer.h"
	#if QT_CONFIG(action)
	#include "qaction.h"
	#endif // QT_CONFIG(action)
	#include "qcursor.h"
	#include "qbitmap.h"
	#include "qtextdocument.h"
	#include <qpa/qplatformtheme.h>
	#include "private/qtextdocumentlayout_p.h"
	#include "qdebug.h"
	#ifndef QT_NO_ACCESSIBILITY
	#include "qaccessible.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
	\inmodule QtWidgets

	"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
	\l{QToolTip}{tooltips}, 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 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.

	\image 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) override;
	void mousePressEvent(QMouseEvent*) override;
	void mouseReleaseEvent(QMouseEvent*) override;
	void mouseMoveEvent(QMouseEvent*) override;
	void keyPressEvent(QKeyEvent*) override;
	void paintEvent(QPaintEvent*) override;

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

	QWhatsThat *QWhatsThat::instance = nullptr;

	// 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;

	static inline bool dropShadow()
	{
	if (const QPlatformTheme *theme = QGuiApplicationPrivate::platformTheme())
	return theme->themeHint(QPlatformTheme::DropShadow).toBool();
	return false;
	}

	QWhatsThat::QWhatsThat(const QString& txt, QWidget* parent, QWidget *showTextFor)
	: QWidget(parent, Qt::Popup),
	widget(showTextFor), pressed(false), text(txt)
	{
	delete instance;
	instance = this;
	setAttribute(Qt::WA_DeleteOnClose, true);
	setAttribute(Qt::WA_NoSystemBackground, true);
	if (parent)
	setPalette(parent->palette());
	setMouseTracking(true);
	setFocusPolicy(Qt::StrongFocus);
	#ifndef QT_NO_CURSOR
	setCursor(Qt::ArrowCursor);
	#endif
	QRect r;
	doc = nullptr;
	ensurePolished(); // Ensures style sheet font before size calc
	if (Qt::mightBeRichText(text)) {
	doc = new QTextDocument();
	doc->setUndoRedoEnabled(false);
	doc->setDefaultFont(QApplication::font(this));
	#ifdef QT_NO_TEXTHTMLPARSER
	doc->setPlainText(text);
	#else
	doc->setHtml(text);
	#endif
	doc->setUndoRedoEnabled(false);
	doc->adjustSize();
	r.setTop(0);
	r.setLeft(0);
	r.setSize(doc->size().toSize());
	}
	else
	{
	int sw = QDesktopWidgetPrivate::width() / 3;
	if (sw < 200)
	sw = 200;
	else if (sw > 300)
	sw = 300;

	r = fontMetrics().boundingRect(0, 0, sw, 1000,
	Qt::AlignLeft + Qt::AlignTop
	+ Qt::TextWordWrap + Qt::TextExpandTabs,
	text);
	}
	shadowWidth = dropShadow() ? 0 : 6;
	resize(r.width() + 2hMargin + shadowWidth, r.height() + 2vMargin + shadowWidth);
	}

	QWhatsThat::~QWhatsThat()
	{
	instance = nullptr;
	if (doc)
	delete doc;
	}

	void QWhatsThat::showEvent(QShowEvent *)
	{
	background = QGuiApplication::primaryScreen()->grabWindow(QApplication::desktop()->internalWinId(),
	x(), y(), width(), height());
	}

	void QWhatsThat::mousePressEvent(QMouseEvent* e)
	{
	pressed = true;
	if (e->button() == Qt::LeftButton && rect().contains(e->pos())) {
	if (doc)
	anchor = doc->documentLayout()->anchorAt(e->pos() - QPoint(hMargin, vMargin));
	return;
	}
	close();
	}

	void QWhatsThat::mouseReleaseEvent(QMouseEvent* e)
	{
	if (!pressed)
	return;
	if (widget && e->button() == Qt::LeftButton && doc && rect().contains(e->pos())) {
	QString a = doc->documentLayout()->anchorAt(e->pos() - QPoint(hMargin, vMargin));
	QString href;
	if (anchor == a)
	href = a;
	anchor.clear();
	if (!href.isEmpty()) {
	QWhatsThisClickedEvent e(href);
	if (QCoreApplication::sendEvent(widget, &e))
	return;
	}
	}
	close();
	}

	void QWhatsThat::mouseMoveEvent(QMouseEvent* e)
	{
	#ifdef QT_NO_CURSOR
	Q_UNUSED(e);
	#else
	if (!doc)
	return;
	QString a = doc->documentLayout()->anchorAt(e->pos() - QPoint(hMargin, vMargin));
	if (!a.isEmpty())
	setCursor(Qt::PointingHandCursor);
	else
	setCursor(Qt::ArrowCursor);
	#endif
	}

	void QWhatsThat::keyPressEvent(QKeyEvent*)
	{
	close();
	}

	void QWhatsThat::paintEvent(QPaintEvent*)
	{
	const bool drawShadow = dropShadow();

	QRect r = rect();
	r.adjust(0, 0, -1, -1);
	if (drawShadow)
	r.adjust(0, 0, -shadowWidth, -shadowWidth);
	QPainter p(this);
	p.drawPixmap(0, 0, background);
	p.setPen(QPen(palette().toolTipText(), 0));
	p.setBrush(palette().toolTipBase());
	p.drawRect(r);
	int w = r.width();
	int h = r.height();
	p.setPen(palette().brush(QPalette::Dark).color());
	p.drawRect(1, 1, w-2, h-2);
	if (drawShadow) {
	p.setPen(palette().shadow().color());
	p.drawPoint(w + 5, 6);
	p.drawLine(w + 3, 6, w + 5, 8);
	p.drawLine(w + 1, 6, w + 5, 10);
	int i;
	for(i=7; i < h; i += 2)
	p.drawLine(w, i, w + 5, i + 5);
	for(i = w - i + h; i > 6; i -= 2)
	p.drawLine(i, h, i + 5, h + 5);
	for(; i > 0 ; i -= 2)
	p.drawLine(6, h + 6 - i, i + 5, h + 5);
	}
	r.adjust(0, 0, 1, 1);
	p.setPen(palette().toolTipText().color());
	r.adjust(hMargin, vMargin, -hMargin, -vMargin);

	if (doc) {
	p.translate(r.x(), r.y());
	QRect rect = r;
	rect.translate(-r.x(), -r.y());
	p.setClipRect(rect);
	QAbstractTextDocumentLayout::PaintContext context;
	context.palette.setBrush(QPalette::Text, context.palette.toolTipText());
	doc->documentLayout()->draw(&p, context);
	}
	else
	{
	p.drawText(r, Qt::AlignLeft + Qt::AlignTop + Qt::TextWordWrap + Qt::TextExpandTabs, text);
	}
	}

	static const char * const button_image[] = {
	"16 16 3 1",
	" c None",
	"o c #000000",
	"a c #000080",
	"o aaaaa ",
	"oo aaa aaa ",
	"ooo aaa aaa",
	"oooo aa aa",
	"ooooo aa aa",
	"oooooo a aaa",
	"ooooooo aaa ",
	"oooooooo aaa ",
	"ooooooooo aaa ",
	"ooooo aaa ",
	"oo ooo ",
	"o ooo aaa ",
	" ooo aaa ",
	" ooo ",
	" ooo ",
	" ooo "};

	class QWhatsThisPrivate : public QObject
	{
	public:
	QWhatsThisPrivate();
	~QWhatsThisPrivate();
	static QWhatsThisPrivate *instance;
	bool eventFilter(QObject , QEvent ) override;
	#if QT_CONFIG(action)
	QPointer<QAction> action;
	#endif // QT_CONFIG(action)
	static void say(QWidget *, const QString &, int x = 0, int y = 0);
	static void notifyToplevels(QEvent *e);
	bool leaveOnMouseRelease;
	};

	void QWhatsThisPrivate::notifyToplevels(QEvent *e)
	{
	const QWidgetList toplevels = QApplication::topLevelWidgets();
	for (auto *w : toplevels)
	QCoreApplication::sendEvent(w, e);
	}

	QWhatsThisPrivate *QWhatsThisPrivate::instance = nullptr;

	QWhatsThisPrivate::QWhatsThisPrivate()
	: leaveOnMouseRelease(false)
	{
	instance = this;
	qApp->installEventFilter(this);

	QPoint pos = QCursor::pos();
	if (QWidget *w = QApplication::widgetAt(pos)) {
	QHelpEvent e(QEvent::QueryWhatsThis, w->mapFromGlobal(pos), pos);
	const bool sentEvent = QCoreApplication::sendEvent(w, &e);
	#ifdef QT_NO_CURSOR
	Q_UNUSED(sentEvent);
	#else
	QGuiApplication::setOverrideCursor((!sentEvent \|\| !e.isAccepted())?
	Qt::ForbiddenCursor:Qt::WhatsThisCursor);
	} else {
	QGuiApplication::setOverrideCursor(Qt::WhatsThisCursor);
	#endif
	}
	#ifndef QT_NO_ACCESSIBILITY
	QAccessibleEvent event(this, QAccessible::ContextHelpStart);
	QAccessible::updateAccessibility(&event);
	#endif
	}

	QWhatsThisPrivate::~QWhatsThisPrivate()
	{
	#if QT_CONFIG(action)
	if (action)
	action->setChecked(false);
	#endif // QT_CONFIG(action)
	#ifndef QT_NO_CURSOR
	QGuiApplication::restoreOverrideCursor();
	#endif
	#ifndef QT_NO_ACCESSIBILITY
	QAccessibleEvent event(this, QAccessible::ContextHelpEnd);
	QAccessible::updateAccessibility(&event);
	#endif
	instance = nullptr;
	}

	bool QWhatsThisPrivate::eventFilter(QObject o, QEvent e)
	{
	if (!o->isWidgetType())
	return false;
	QWidget * w = static_cast<QWidget *>(o);
	bool customWhatsThis = w->testAttribute(Qt::WA_CustomWhatsThis);
	switch (e->type()) {
	case QEvent::MouseButtonPress:
	{
	QMouseEvent me = static_cast<QMouseEvent>(e);
	if (me->button() == Qt::RightButton \|\| customWhatsThis)
	return false;
	QHelpEvent e(QEvent::WhatsThis, me->pos(), me->globalPos());
	if (!QCoreApplication::sendEvent(w, &e) \|\| !e.isAccepted())
	leaveOnMouseRelease = true;

	} break;

	case QEvent::MouseMove:
	{
	QMouseEvent me = static_cast<QMouseEvent>(e);
	QHelpEvent e(QEvent::QueryWhatsThis, me->pos(), me->globalPos());
	const bool sentEvent = QCoreApplication::sendEvent(w, &e);
	#ifdef QT_NO_CURSOR
	Q_UNUSED(sentEvent);
	#else
	QGuiApplication::changeOverrideCursor((!sentEvent \|\| !e.isAccepted())?
	Qt::ForbiddenCursor:Qt::WhatsThisCursor);
	#endif
	Q_FALLTHROUGH();
	}
	case QEvent::MouseButtonRelease:
	case QEvent::MouseButtonDblClick:
	if (leaveOnMouseRelease && e->type() == QEvent::MouseButtonRelease)
	QWhatsThis::leaveWhatsThisMode();
	if (static_cast<QMouseEvent*>(e)->button() == Qt::RightButton \|\| customWhatsThis)
	return false; // ignore RMB release
	break;
	case QEvent::KeyPress:
	{
	QKeyEvent* kev = (QKeyEvent*)e;
	#if QT_CONFIG(shortcut)
	if (kev->matches(QKeySequence::Cancel)) {
	QWhatsThis::leaveWhatsThisMode();
	return true;
	} else
	#endif
	if (customWhatsThis) {
	return false;
	} else if (kev->key() == Qt::Key_Menu \|\|
	(kev->key() == Qt::Key_F10 &&
	kev->modifiers() == Qt::ShiftModifier)) {
	// we don't react to these keys, they are used for context menus
	return false;
	} else if (kev->key() != Qt::Key_Shift && kev->key() != Qt::Key_Alt // not a modifier key
	&& kev->key() != Qt::Key_Control && kev->key() != Qt::Key_Meta) {
	QWhatsThis::leaveWhatsThisMode();
	}
	} break;
	default:
	return false;
	}
	return true;
	}

	#if QT_CONFIG(action)
	class QWhatsThisAction: public QAction
	{
	Q_OBJECT

	public:
	explicit QWhatsThisAction(QObject* parent = nullptr);

	private slots:
	void actionTriggered();
	};

	QWhatsThisAction::QWhatsThisAction(QObject *parent) : QAction(tr("What's This?"), parent)
	{
	#ifndef QT_NO_IMAGEFORMAT_XPM
	QPixmap p(button_image);
	setIcon(p);
	#endif
	setCheckable(true);
	connect(this, SIGNAL(triggered()), this, SLOT(actionTriggered()));
	#ifndef QT_NO_SHORTCUT
	setShortcut(Qt::ShiftModifier + Qt::Key_F1);
	#endif
	}

	void QWhatsThisAction::actionTriggered()
	{
	if (isChecked()) {
	QWhatsThis::enterWhatsThisMode();
	QWhatsThisPrivate::instance->action = this;
	}
	}
	#endif // QT_CONFIG(action)

	/*!
	This function switches the user interface into "What's This?"
	mode. The user interface can be switched back into normal mode by
	the user (e.g. by them clicking or pressing Esc), or
	programmatically by calling leaveWhatsThisMode().

	When entering "What's This?" mode, a QEvent of type
	Qt::EnterWhatsThisMode is sent to all toplevel widgets.

	\sa inWhatsThisMode(), leaveWhatsThisMode()
	*/
	void QWhatsThis::enterWhatsThisMode()
	{
	if (QWhatsThisPrivate::instance)
	return;
	(void) new QWhatsThisPrivate;
	QEvent e(QEvent::EnterWhatsThisMode);
	QWhatsThisPrivate::notifyToplevels(&e);
	}

	/*!
	Returns \c true if the user interface is in "What's This?" mode;
	otherwise returns \c false.

	\sa enterWhatsThisMode()
	*/
	bool QWhatsThis::inWhatsThisMode()
	{
	return (QWhatsThisPrivate::instance != nullptr);
	}

	/*!
	If the user interface is in "What's This?" mode, this function
	switches back to normal mode; otherwise it does nothing.

	When leaving "What's This?" mode, a QEvent of type
	Qt::LeaveWhatsThisMode is sent to all toplevel widgets.

	\sa enterWhatsThisMode(), inWhatsThisMode()
	*/
	void QWhatsThis::leaveWhatsThisMode()
	{
	delete QWhatsThisPrivate::instance;
	QEvent e(QEvent::LeaveWhatsThisMode);
	QWhatsThisPrivate::notifyToplevels(&e);
	}

	void QWhatsThisPrivate::say(QWidget * widget, const QString &text, int x, int y)
	{
	if (text.size() == 0)
	return;
	// make a fresh widget, and set it up
	QWhatsThat *whatsThat = new QWhatsThat(text, nullptr, widget);

	// okay, now to find a suitable location
	int scr = (widget ?
	QDesktopWidgetPrivate::screenNumber(widget) :
	QDesktopWidgetPrivate::screenNumber(QPoint(x,y))
	);
	QRect screen = QDesktopWidgetPrivate::screenGeometry(scr);

	int w = whatsThat->width();
	int h = whatsThat->height();
	int sx = screen.x();
	int sy = screen.y();

	// first try locating the widget immediately above/below,
	// with nice alignment if possible.
	QPoint pos;
	if (widget)
	pos = widget->mapToGlobal(QPoint(0,0));

	if (widget && w > widget->width() + 16)
	x = pos.x() + widget->width()/2 - w/2;
	else
	x = x - w/2;

	// squeeze it in if that would result in part of what's this
	// being only partially visible
	if (x + w + shadowWidth > sx+screen.width())
	x = (widget? (qMin(screen.width(),
	pos.x() + widget->width())
	) : screen.width())
	- w;

	if (x < sx)
	x = sx;

	if (widget && h > widget->height() + 16) {
	y = pos.y() + widget->height() + 2; // below, two pixels spacing
	// what's this is above or below, wherever there's most space
	if (y + h + 10 > sy+screen.height())
	y = pos.y() + 2 - shadowWidth - h; // above, overlap
	}
	y = y + 2;

	// squeeze it in if that would result in part of what's this
	// being only partially visible
	if (y + h + shadowWidth > sy+screen.height())
	y = (widget ? (qMin(screen.height(),
	pos.y() + widget->height())
	) : screen.height())
	- h;
	if (y < sy)
	y = sy;

	whatsThat->move(x, y);
	whatsThat->show();
	whatsThat->grabKeyboard();
	}

	/*!
	Shows \a text as a "What's This?" window, at global position \a
	pos. The optional widget argument, \a w, is used to determine the
	appropriate screen on multi-head systems.

	\sa hideText()
	*/
	void QWhatsThis::showText(const QPoint &pos, const QString &text, QWidget *w)
	{
	leaveWhatsThisMode();
	QWhatsThisPrivate::say(w, text, pos.x(), pos.y());
	}

	/*!
	If a "What's This?" window is showing, this destroys it.

	\sa showText()
	*/
	void QWhatsThis::hideText()
	{
	qDeleteInEventHandler(QWhatsThat::instance);
	}

	/*!
	Returns a ready-made QAction, used to invoke "What's This?" context
	help, with the given \a parent.

	The returned QAction provides a convenient way to let users enter
	"What's This?" mode.
	*/
	#if QT_CONFIG(action)
	QAction QWhatsThis::createAction(QObject parent)
	{
	return new QWhatsThisAction(parent);
	}
	#endif // QT_CONFIG(action)

	QT_END_NAMESPACE

	#include "qwhatsthis.moc"