okular/part/cursorwraphelper.h
2021-06-10 08:11:56 +00:00

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/*
SPDX-FileCopyrightText: 2020 David Hurka <david.hurka@mailbox.org>
SPDX-License-Identifier: GPL-2.0-or-later
*/
#ifndef CURSORWRAPHELPER_H
#define CURSORWRAPHELPER_H
#include <QPoint>
#include <QPointer>
class QScreen;
/**
* Wrap the cursor around screen edges.
*
* Problem: When setting the cursor position,
* the actual wrap operation may happen later or not at all.
* Your application needs to observe the actual wrap operation,
* and calculate movement offsets based on this operation.
*
* This class provides this functionality in a single static function.
*
* Example:
* \code
* MyWidget::mousePressEvent(QMouseEvent *me)
* {
* CursorWrapHelper::startDrag();
* m_lastCursorPos = me->pos();
* }
*
* MyWidget::mouseMoveEvent(QMouseEvent *me)
* {
* cursorMovement = me->pos() - m_lastCursorPos;
* cursorMovement -= CursorWrapHelper::wrapCursor(me->pos(), Qt::TopEdge | Qt::BottomEdge);
*
* ...
* processMovement(cursorMovement);
* ...
* }
* \endcode
*/
class CursorWrapHelper
{
public:
/**
* Wrap the QCursor around specified screen edges.
*
* Wrapping is performed using QCursor::pos().
* You have to provide a cursor position, because QCursor::pos() is realtime,
* which means it can not be used to calculate the resulting offset for you.
* If you implement mousePressEvent() and mouseMoveEvent(),
* you can simply pass event->pos().
* @p eventPosition may have a constant offset.
*
* @param eventPosition The cursor position you are currently working with.
* @param edges At which edges to wrap. (E. g. top -> bottom: use Qt::TopEdge)
* @returns The actual distance the cursor was moved.
*/
static QPoint wrapCursor(QPoint eventPosition, Qt::Edges edges);
/**
* Call this to avoid computing a wrap distance when a drag starts.
*
* This should be called every time you get e. g. a mousePressEvent().
*/
static void startDrag();
protected:
/** Returns the screen under the cursor */
static QScreen *getScreen();
/** Remember screen to speed up screen search */
static QPointer<QScreen> s_lastScreen;
/**
* Actual wrapping of the cursor may happen later.
* By comparing the magnitude of cursor movements to the last wrap operation,
* we can catch the moment when wrapping actually happens,
* and return the wrapping offset at that time.
*
* Vertical wrapping and horizontal wrapping may happen with little delay,
* so they are handled strictly separately.
*/
static QPoint s_lastCursorPosition;
static QPoint s_lastWrapOperation;
/**
* If the user releases the mouse while it is being wrapped,
* we dont want the wrap to be subtracted from the next drag operation.
* This timestamp allows to check whether the user possibly started a new drag.
*/
static QPoint s_lastTimeStamp;
};
#endif // CURSORWRAPHELPER_H