shift-shell/libmobileshell/declarative/qml/navigationpanel/NavigationGestureArea.qml

/*
 *  SPDX-FileCopyrightText: 2015 Marco Martin <mart@kde.org>
 *  SPDX-FileCopyrightText: 2022 Devin Lin <devin@kde.org>
 *
 *  SPDX-License-Identifier: GPL-2.0-or-later
 */

import QtQuick 2.4
import QtQuick.Layouts 1.1
import QtQuick.Window 2.2
import QtGraphicalEffects 1.12

import org.kde.taskmanager 0.1 as TaskManager
import org.kde.plasma.core 2.0 as PlasmaCore
import org.kde.kquickcontrolsaddons 2.0

import org.kde.plasma.private.nanoshell 2.0 as NanoShell
import org.kde.plasma.private.mobileshell 1.0 as MobileShell

Item {
    id: root

    property var taskSwitcher
    
    MouseArea {
        id: mouseArea
        anchors.fill: parent
        drag.filterChildren: true
        
        // drag gesture
        property int oldMouseY: 0
        property int startMouseY: 0
        property int oldMouseX: 0
        property int startMouseX: 0
        property bool opening: false
        
        onPressed: {
            startMouseX = oldMouseX = mouse.y;
            startMouseY = oldMouseY = mouse.y;
        }
        
        onPositionChanged: {
            if (!opening && Math.abs(startMouseY - oldMouseY) < root.height) {
                oldMouseY = mouse.y;
                return;
            } else if (mouseArea.pressed) {
                opening = true;
            }

            if (root.taskSwitcher.visible) {
                // update task switcher drag
                let offsetY = (mouse.y - oldMouseY) * 0.5; // we want to make the gesture take a longer swipe than it being pixel perfect
                let offsetX = (mouse.x - oldMouseX) * 0.7; // we want to make the gesture not too hard to swipe, but not too easy
                taskSwitcher.taskSwitcherState.yPosition = Math.max(0, taskSwitcher.taskSwitcherState.yPosition - offsetY);
                taskSwitcher.taskSwitcherState.xPosition -= offsetX;
            }

            if (!root.taskSwitcher.visible && Math.abs(startMouseY - mouse.y) > PlasmaCore.Units.gridUnit && taskSwitcher.tasksCount) {
                // start task switcher gesture
                root.taskSwitcher.show(false);
            }
            
            oldMouseY = mouse.y;
            oldMouseX = mouse.x;
        }
        
        onReleased: {
            if (taskSwitcher.taskSwitcherState.currentlyBeingOpened) {
                taskSwitcher.taskSwitcherState.updateState();
            }
        }
    }
}