[plasma-mobile/qmlkonsole] src: Implement inertial scrolling for touch in terminal view

Git commit b0d72eb8eb70e9c739469dc4dc79b220fa99f90f by Devin Lin.
Committed on 19/07/2026 at 16:18.
Pushed by devinlin into branch 'master'.

Implement inertial scrolling for touch in terminal view

M  +3    -12   src/contents/ui/TerminalPage.qml
A  +125  -0    src/contents/ui/TerminalTouchScrollHandler.qml     [License: GPL(v2.0+)]
M  +1    -0    src/resources.qrc

https://invent.kde.org/plasma-mobile/qmlkonsole/-/commit/b0d72eb8eb70e9c739469dc4dc79b220fa99f90f

diff --git a/src/contents/ui/TerminalPage.qml b/src/contents/ui/TerminalPage.qml
index 42f81fe..502b171 100644
--- a/src/contents/ui/TerminalPage.qml
+++ b/src/contents/ui/TerminalPage.qml
@@ -546,19 +546,10 @@ Kirigami.Page {
                             onLongPressed: terminal.touchSelectionMode = true
                         }
 
-                        // simulate scrolling for touch (TODO velocity)
-                        DragHandler {
-                            acceptedDevices: PointerDevice.TouchScreen
+                        TerminalTouchScrollHandler {
+                            anchors.fill: parent
                             enabled: !terminal.touchSelectionMode
-
-                            property real previousY
-                            onActiveChanged: {
-                                previousY = 0;
-                            }
-                            onTranslationChanged: {
-                                terminal.simulateWheel(0, 0, 0, 0, Qt.point(0, (translation.y - previousY) * 2));
-                                previousY = translation.y;
-                            }
+                            terminalItem: terminal
                         }
                     }
                 }
diff --git a/src/contents/ui/TerminalTouchScrollHandler.qml b/src/contents/ui/TerminalTouchScrollHandler.qml
new file mode 100644
index 0000000..3bc16b4
--- /dev/null
+++ b/src/contents/ui/TerminalTouchScrollHandler.qml
@@ -0,0 +1,125 @@
+// SPDX-FileCopyrightText: 2019-2020 Jonah Brüchert <[email protected]>
+// SPDX-FileCopyrightText: 2021-2022 Devin Lin <[email protected]>
+//
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+import QtQuick
+
+import org.kde.konsoleqml
+
+Item {
+    id: root
+
+    required property TerminalEmulator terminalItem
+
+    onEnabledChanged: {
+        if (!enabled) {
+            touchScrollHandler.stopInertia();
+        }
+    }
+
+    TapHandler {
+        acceptedDevices: PointerDevice.TouchScreen
+        onPressedChanged: {
+            if (pressed) {
+                touchScrollHandler.pauseInertia();
+            }
+        }
+        onTapped: touchScrollHandler.stopInertia()
+    }
+
+    DragHandler {
+        id: touchScrollHandler
+
+        acceptedDevices: PointerDevice.TouchScreen
+        target: null
+        xAxis.enabled: false
+
+        property real inertialY
+        property real previousInertialY
+        property real wheelRemainder
+        property real carriedVelocity
+        property real initialInertialVelocity
+        property double inertiaStartedAt
+
+        readonly property real maximumVelocity: 10000
+        readonly property real minimumVelocity: 50
+        readonly property real deceleration: 2500
+
+        function scrollBy(pixelDelta) {
+            wheelRemainder += pixelDelta * 2;
+
+            const wheelDelta = wheelRemainder < 0 ? Math.ceil(wheelRemainder) : Math.floor(wheelRemainder);
+            if (wheelDelta === 0) {
+                return;
+            }
+
+            root.terminalItem.simulateWheel(0, 0, 0, 0, Qt.point(0, wheelDelta));
+            wheelRemainder -= wheelDelta;
+        }
+
+        function pauseInertia() {
+            if (!touchScrollAnimation.running) {
+                return;
+            }
+
+            const elapsed = (Date.now() - inertiaStartedAt) / 1000;
+            carriedVelocity = Math.sign(initialInertialVelocity)
+                * Math.max(0, Math.abs(initialInertialVelocity) - deceleration * elapsed);
+            touchScrollAnimation.stop();
+        }
+
+        function stopInertia() {
+            touchScrollAnimation.stop();
+            carriedVelocity = 0;
+            initialInertialVelocity = 0;
+        }
+
+        onActiveChanged: {
+            if (active) {
+                pauseInertia();
+                return;
+            }
+
+            let velocity = centroid.velocity.y;
+            if (Math.abs(velocity) < minimumVelocity) {
+                stopInertia();
+                return;
+            }
+
+            if (velocity * carriedVelocity > 0) {
+                velocity += carriedVelocity;
+            }
+            velocity = Math.max(-maximumVelocity, Math.min(maximumVelocity, velocity));
+
+            carriedVelocity = 0;
+            initialInertialVelocity = velocity;
+            inertiaStartedAt = Date.now();
+            previousInertialY = 0;
+            inertialY = 0;
+            touchScrollAnimation.to = velocity * Math.abs(velocity) / (2 * deceleration);
+            touchScrollAnimation.duration = Math.round(Math.abs(velocity) / deceleration * 1000);
+            touchScrollAnimation.restart();
+        }
+        yAxis.onActiveValueChanged: delta => {
+            if (active) {
+                scrollBy(delta);
+            }
+        }
+        onInertialYChanged: {
+            scrollBy(inertialY - previousInertialY);
+            previousInertialY = inertialY;
+        }
+    }
+
+    NumberAnimation {
+        id: touchScrollAnimation
+        target: touchScrollHandler
+        property: "inertialY"
+        easing.type: Easing.OutQuad
+        onFinished: {
+            touchScrollHandler.carriedVelocity = 0;
+            touchScrollHandler.initialInertialVelocity = 0;
+        }
+    }
+}
diff --git a/src/resources.qrc b/src/resources.qrc
index d8e5825..30d5e63 100644
--- a/src/resources.qrc
+++ b/src/resources.qrc
@@ -10,6 +10,7 @@
         <file alias="SettingsPage.qml">contents/ui/SettingsPage.qml</file>
         <file alias="SettingsDialog.qml">contents/ui/SettingsDialog.qml</file>
         <file alias="TerminalPage.qml">contents/ui/TerminalPage.qml</file>
+        <file alias="TerminalTouchScrollHandler.qml">contents/ui/TerminalTouchScrollHandler.qml</file>
         <file alias="TerminalKeyButton.qml">contents/ui/TerminalKeyButton.qml</file>
         <file alias="TerminalKeyToolBar.qml">contents/ui/TerminalKeyToolBar.qml</file>
         <file alias="SavedCommandsSettings.qml">contents/ui/SavedCommandsSettings.qml</file>