From 617ba59de770aa15400a8ac750ce1378c3519b45 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Luis=20B=C3=BCchi?= <luis.buechi@server23.cc>
Date: Wed, 24 Jul 2024 10:57:57 +0000
Subject: [PATCH] add haptic feedback to task switcher gestures

haptics are triggered when conditions are met to open task switcher or task scrub mode is engaged.
fixes related bug in task switcher gesture logic when invoked from homescreen

fixes https://invent.kde.org/plasma/plasma-mobile/-/issues/366
---
 kwin/mobiletaskswitcher/qml/TaskSwitcher.qml  | 33 ++++++++++++++++++-
 .../qml/TaskSwitcherHelpers.qml               |  4 +++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/kwin/mobiletaskswitcher/qml/TaskSwitcher.qml b/kwin/mobiletaskswitcher/qml/TaskSwitcher.qml
index a9018c03..c44d5d9a 100644
--- a/kwin/mobiletaskswitcher/qml/TaskSwitcher.qml
+++ b/kwin/mobiletaskswitcher/qml/TaskSwitcher.qml
@@ -39,6 +39,10 @@ FocusScope {
         stateClass: TaskSwitcherData.TaskSwitcherState
     }
 
+    MobileShell.HapticsEffect {
+        id: haptics
+    }
+
     property var tasksModel: TaskSwitcherData.TaskFilterModel {
         screenName: root.targetScreen.name
         windowModel: TaskSwitcherData.TaskModel
@@ -102,6 +106,12 @@ FocusScope {
                 taskSwitcherHelpers.isInTaskScrubMode = true;
                 taskSwitcherHelpers.cancelAnimations();
                 taskSwitcherHelpers.open();
+                if (!taskSwitcherHelpers.hasVibrated) {
+                    // Haptic feedback when the task scrub mode engages
+                    haptics.buttonVibrate();
+                    taskSwitcherHelpers.hasVibrated = true;
+                }
+
             }
             let newTaskIndex = Math.max(0, Math.min(tasksCount - 1, Math.floor(state.touchXPosition / taskSwitcherHelpers.taskScrubDistance) + state.initialTaskIndex));
             if (newTaskIndex != state.currentTaskIndex) {
@@ -217,12 +227,33 @@ FocusScope {
                         taskSwitcherHelpers.open();
                     } else {
                         // no flick and not enough activation to go to task switcher
-                        returnToApp();
+                        if (state.wasInActiveTask) {
+                            returnToApp();
+                        } else {
+                            // do open switcher in case we were on homescreen before
+                            taskSwitcherHelpers.animateGoToTaskIndex(state.currentTaskIndex);
+                            taskSwitcherHelpers.open();
+                        }
+
                     }
                 }
             }
         }
 
+        function onVelocityChanged() {
+            if (!taskSwitcherHelpers.hasVibrated) {
+                if (!state.wasInActiveTask ||
+                    (state.wasInActiveTask &&
+                     state.yPosition > taskSwitcherHelpers.undoYThreshold &&
+                     state.totalSquaredVelocity < state.flickVelocityThreshold)) {
+                        // Haptic feedback when conditions are met for the task switcher to open
+                        haptics.buttonVibrate();
+                        taskSwitcherHelpers.hasVibrated = true;
+                }
+
+            }
+        }
+
         function onXPositionChanged() {
             taskSwitcherHelpers.updateTaskIndex();
         }
diff --git a/kwin/mobiletaskswitcher/qml/TaskSwitcherHelpers.qml b/kwin/mobiletaskswitcher/qml/TaskSwitcherHelpers.qml
index 91b44328..3bf1c6d2 100644
--- a/kwin/mobiletaskswitcher/qml/TaskSwitcherHelpers.qml
+++ b/kwin/mobiletaskswitcher/qml/TaskSwitcherHelpers.qml
@@ -33,6 +33,10 @@ QtObject {
     // yPosition threshold below which opening the task switcher should be undone and returned to the previously active task
     readonly property real undoYThreshold: openedYPosition / 2
 
+    // whether the switcher has already triggered haptic feedback or not
+    // we don't want to continuously send haptics, just once is enough
+    property bool hasVibrated: false
+
     // ~~ measurement constants ~~
 
     // dimensions of a real window on the screen