add double tap to switch between 2 most recent apps in swicher

also simplified openApp signature and fixed a typo in code
FEATURE: 486555

kwin/mobiletaskswitcher/mobiletaskswitchereffect.cpp

@@ -1,6 +1,6 @@
 // SPDX-FileCopyrightText: 2021 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
 // SPDX-FileCopyrightText: 2023 Devin Lin <devin@kde.org>
-// SPDX-FileCopyrightText: 2024 Luis Büchi <luis.buechi@server23.cc>
+// SPDX-FileCopyrightText: 2024 Luis Büchi <luis.buechi@kdemail.net>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "mobiletaskswitchereffect.h"
@@ -20,6 +20,7 @@ namespace KWin
 
 MobileTaskSwitcherState::MobileTaskSwitcherState(EffectTouchBorderState *effectState)
     : m_effectState{effectState}
+    , m_doubleClickTimer{new QElapsedTimer{}}
 {
     connect(m_effectState, &EffectTouchBorderState::inProgressChanged, this, &MobileTaskSwitcherState::gestureInProgressChanged);
 }
@@ -150,6 +151,11 @@ void MobileTaskSwitcherState::setInitialTaskIndex(int newTaskIndex)
     }
 }
 
+void MobileTaskSwitcherState::restartDoubleClickTimer()
+{
+    m_doubleClickTimer->restart();
+}
+
 void MobileTaskSwitcherState::calculateFilteredVelocity(qreal primaryDelta, qreal orthogonalDelta)
 {
     static qreal prevPrimaryDelta = 0;
@@ -190,6 +196,15 @@ void MobileTaskSwitcherState::processTouchPositionChanged(qreal primaryDelta, qr
     Q_EMIT touchPositionChanged();
 }
 
+qint64 MobileTaskSwitcherState::getElapsedTimeSinceStart()
+{
+    if (m_doubleClickTimer->isValid())
+    {
+        return m_doubleClickTimer->elapsed();
+    }
+    return -1;
+}
+
 MobileTaskSwitcherEffect::MobileTaskSwitcherEffect()
     : m_effectState{new EffectTouchBorderState(this)}
     , m_taskSwitcherState{new MobileTaskSwitcherState(m_effectState)}
@@ -269,6 +284,7 @@ void MobileTaskSwitcherEffect::grabbedKeyboardEvent(QKeyEvent *keyEvent)
 void MobileTaskSwitcherEffect::toggle()
 {
     if (!isRunning()) {
+        m_taskSwitcherState->restartDoubleClickTimer();
         activate();
     } else {
         deactivate(false);

kwin/mobiletaskswitcher/mobiletaskswitchereffect.h

@@ -1,6 +1,6 @@
 // SPDX-FileCopyrightText: 2021 Vlad Zahorodnii <vlad.zahorodnii@kde.org>
 // SPDX-FileCopyrightText: 2023 Devin Lin <devin@kde.org>
-// SPDX-FileCopyrightText: 2024 Luis Büchi <luis.buechi@server23.cc>
+// SPDX-FileCopyrightText: 2024 Luis Büchi <luis.buechi@kdemail.net>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
@@ -48,6 +48,9 @@ class MobileTaskSwitcherState : public QObject
     Q_PROPERTY(bool gestureInProgress READ gestureInProgress NOTIFY gestureInProgressChanged)
     Q_PROPERTY(Status status READ status WRITE setStatus NOTIFY statusChanged)
 
+    Q_PROPERTY(qint64 elapsedTimeSinceStart READ getElapsedTimeSinceStart)
+    Q_PROPERTY(qint64 doubleClickInterval READ getDoubleClickInterval) // is there a better way than to forward this?
+
 public:
     enum class Status {
         // TODO! I could (should?) re-add the activating and deactivating states again to match EffectTogglableState. could help with/tie into
@@ -97,6 +100,8 @@ public:
         return m_initialTaskIndex;
     }
 
+    void restartDoubleClickTimer();
+
 public Q_SLOTS:
     void processTouchPositionChanged(qreal primaryPosition, qreal orthogonalPosition);
 
@@ -130,6 +135,7 @@ private:
 
     void clearVelocityFilter();
     void calculateFilteredVelocity(qreal primaryPosition, qreal orthogonalPosition);
+    qint64 getElapsedTimeSinceStart();
 
     // velocities in (logical) pixels/msec
     QElapsedTimer m_frameTimer;
@@ -149,6 +155,12 @@ private:
     qreal m_yPosition = 0;
 
     bool m_wasInActiveTask;
+
+    QElapsedTimer *m_doubleClickTimer;
+    qint64 getDoubleClickInterval() const
+    {
+        return qApp->doubleClickInterval();
+    }
 };
 
 class MobileTaskSwitcherEffect : public QuickSceneEffect

kwin/mobiletaskswitcher/qml/Task.qml

@@ -1,5 +1,6 @@
 // SPDX-FileCopyrightText: 2015 Marco Martin <notmart@gmail.com>
 // SPDX-FileCopyrightText: 2021-2023 Devin Lin <devin@kde.org>
+// SPDX-FileCopyrightText: 2024 Luis Büchi <luis.buechi@kdemail.net>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 import QtQuick
@@ -48,7 +49,7 @@ Item {
         if (!ShellSettings.Settings.convergenceModeEnabled) {
             delegate.window.setMaximize(true, true);
         }
-        taskSwitcherHelpers.openApp(model.index, delegate.window);
+        taskSwitcherHelpers.openApp(model.index);
     }
 
     function minimizeApp() {

kwin/mobiletaskswitcher/qml/TaskSwitcher.qml

@@ -1,5 +1,6 @@
 // SPDX-FileCopyrightText: 2015 Marco Martin <notmart@gmail.com>
 // SPDX-FileCopyrightText: 2021-2024 Devin Lin <devin@kde.org>
+// SPDX-FileCopyrightText: 2024 Luis Büchi <luis.buechi@kdemail.net>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 import QtQuick
@@ -37,6 +38,7 @@ FocusScope {
     property var taskSwitcherHelpers: TaskSwitcherHelpers {
         taskSwitcher: root
         stateClass: TaskSwitcherData.TaskSwitcherState
+        taskList: taskList
     }
 
     MobileShell.HapticsEffect {
@@ -308,8 +310,7 @@ FocusScope {
         // if accidentally invoked, but can also be used to switch to an adjacent app and then open it
         function returnToApp() {
             let newIndex = taskSwitcherHelpers.getNearestTaskIndex();
-            let appAtNewIndex = taskList.getTaskAt(newIndex).window;
+            taskSwitcherHelpers.openApp(newIndex);
-            taskSwitcherHelpers.openApp(newIndex, appAtNewIndex);
         }
 
         // diagonal quick switch gesture logic
@@ -338,15 +339,14 @@ FocusScope {
                 } else {
                     // flick to the left on the home screen, dismiss the gesture
                     taskSwitcherHelpers.close();
-                    retrun;
+                    return;
                 }
             }
             if (shouldSwitch) {
                 if (!taskSwitcherHelpers.taskDrawerOpened && unmodifiedYposition < taskSwitcherHelpers.openedYPosition) {
                     // if in a app, switch it to the new task when it is under the openedYPosition
                     taskList.setTaskOffsetValue(0, unmodifiedYposition < taskSwitcherHelpers.openedYPosition && taskSwitcherHelpers.notHomeScreenState);
-                    let appAtNewIndex = taskList.getTaskAt(newIndex).window;
+                    taskSwitcherHelpers.openApp(newIndex, Kirigami.Units.longDuration * 4, Easing.OutExpo);
-                    taskSwitcherHelpers.openApp(newIndex, appAtNewIndex, Kirigami.Units.longDuration * 4, Easing.OutExpo);
                 } else {
                     // if already in the task switcher or above the openedYPosition, only change the focus to the new task
                     taskSwitcherHelpers.animateGoToTaskIndex(newIndex);
@@ -380,7 +380,7 @@ FocusScope {
                     taskSwitcherHelpers.open();
                     taskSwitcherHelpers.isInTaskScrubMode = false;
                 } else {
-                    taskSwitcherHelpers.openApp(state.currentTaskIndex, taskList.getTaskAt(state.currentTaskIndex).window);
+                    taskSwitcherHelpers.openApp(state.currentTaskIndex);
                 }
             } else if (taskSwitcherHelpers.gestureState == TaskSwitcherHelpers.GestureStates.Undecided) {
                 if (taskSwitcherHelpers.taskDrawerOpened) {
@@ -499,8 +499,15 @@ FocusScope {
                 if (taskList.count === 0) {
                     root.hide();
                 } else {
+                    if (taskList.count > 1 &&
+                        state.elapsedTimeSinceStart != -1 &&
+                        state.elapsedTimeSinceStart < state.doubleClickInterval) {
+                        taskSwitcherHelpers.openApp(1);
+                        return;
+                    }
+
                     const currentIndex = state.currentTaskIndex;
-                    taskSwitcherHelpers.openApp(state.currentTaskIndex, taskList.getTaskAt(currentIndex).window);
+                    taskSwitcherHelpers.openApp(state.currentTaskIndex);
                 }
             }
         }

kwin/mobiletaskswitcher/qml/TaskSwitcherHelpers.qml

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: 2021 Devin Lin <devin@kde.org>
+// SPDX-FileCopyrightText: 2024 Luis Büchi <luis.buechi@kdemail.net>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 import QtQuick 2.15
@@ -19,6 +20,7 @@ QtObject {
     required property var taskSwitcher
     property var state: taskSwitcher.state
     required property var stateClass
+    required property var taskList
 
     // task switcher peek and pop setting for when it is toggled from the home screen
     readonly property real peekOffsetValue: 1.85
@@ -217,14 +219,14 @@ QtObject {
         closeFactorAnim.restart();
     }
 
-    function openApp(index, window, duration = Kirigami.Units.shortDuration, horizontalEasing = Easing.OutBack) {
+    function openApp(index, duration = Kirigami.Units.shortDuration, horizontalEasing = Easing.OutBack) {
         // cancel any opening animations ongoing
         openAnim.stop();
         cancelAnimations();
 
         animateGoToTaskIndex(index, duration);
         openAppAnim.restart();
-        KWinComponents.Workspace.activeWindow = window
+        KWinComponents.Workspace.activeWindow = taskList.getTaskAt(index).window;
     }
 
     // get the xPosition where the task will be centered on the screen