[gnome-shell/wip/exalm/gestures-part-3: 1/4] swipeTracker: Introduce swipe tracker

[Alexander Mikhaylenko <alexm src gnome org>]

commit c30fad6990116dba8972eb79a2d2a43913171884
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Sun Jun 30 17:11:27 2019 +0500

    swipeTracker: Introduce swipe tracker
    
    Add a unified swipe tracker supporting dragging, four-finger swipe on both
    touchscreen and touchpad, and touchpad scrolling.
    
    The shared logic is largely same as the one in WebKit and libhandy.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/826

 js/js-resources.gresource.xml |   1 +
 js/ui/swipeTracker.js         | 501 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 502 insertions(+)
---
diff --git a/js/js-resources.gresource.xml b/js/js-resources.gresource.xml
index b5348ddcb5..aec3427e0b 100644
--- a/js/js-resources.gresource.xml
+++ b/js/js-resources.gresource.xml
@@ -98,6 +98,7 @@
     <file>ui/shellEntry.js</file>
     <file>ui/shellMountOperation.js</file>
     <file>ui/slider.js</file>
+    <file>ui/swipeTracker.js</file>
     <file>ui/switcherPopup.js</file>
     <file>ui/switchMonitor.js</file>
     <file>ui/tweener.js</file>
diff --git a/js/ui/swipeTracker.js b/js/ui/swipeTracker.js
new file mode 100644
index 0000000000..6a3d021bad
--- /dev/null
+++ b/js/ui/swipeTracker.js
@@ -0,0 +1,501 @@
+// -*- mode: js; js-indent-level: 4; indent-tabs-mode: nil -*-
+/* exported SwipeTracker */
+
+const { Clutter, Gio, GObject, Meta } = imports.gi;
+
+const Signals = imports.signals;
+
+const Main = imports.ui.main;
+
+// FIXME: ideally this value matches physical touchpad size. We can get this
+// value for gnome-shell specifically, since mutter uses libinput directly,
+// but GTK apps cannot get it, so use an arbitrary value so that it's
+// consistent with apps instead.
+const TOUCHPAD_BASE_DISTANCE_V = 300;
+const TOUCHPAD_BASE_DISTANCE_H = 400;
+const SCROLL_MULTIPLIER = 10;
+const SWIPE_MULTIPLIER = 0.5;
+
+const MIN_ANIMATION_DURATION = 100;
+const MAX_ANIMATION_DURATION = 400;
+const VELOCITY_THRESHOLD = 0.4;
+const DURATION_MULTIPLIER = 3;
+const ANIMATION_BASE_VELOCITY = 0.002;
+
+var State = {
+    NONE: 0,
+    SCROLLING: 1,
+};
+
+function clamp(value, min, max) {
+    return Math.max(min, Math.min(max, value));
+}
+
+var TouchpadSwipeGesture = class TouchpadSwipeGesture {
+    constructor(shouldSkip) {
+        this._shouldSkip = shouldSkip;
+        this._touchpadSettings = new Gio.Settings({
+            schema_id: 'org.gnome.desktop.peripherals.touchpad',
+        });
+        this._orientation = Clutter.Orientation.VERTICAL;
+
+        global.stage.connect('captured-event', this._handleEvent.bind(this));
+    }
+
+    _handleEvent(_actor, event) {
+        if (event.type() != Clutter.EventType.TOUCHPAD_SWIPE)
+            return Clutter.EVENT_PROPAGATE;
+
+        if (event.get_touchpad_gesture_finger_count() != 4)
+            return Clutter.EVENT_PROPAGATE;
+
+        if (this._shouldSkip())
+            return Clutter.EVENT_PROPAGATE;
+
+        let time = event.get_time();
+
+        let [x, y] = event.get_coords();
+        let [dx, dy] = event.get_gesture_motion_delta();
+
+        let delta;
+        if (this._orientation == Clutter.Orientation.VERTICAL)
+            delta = dy / TOUCHPAD_BASE_DISTANCE_V;
+        else
+            delta = dx / TOUCHPAD_BASE_DISTANCE_H;
+
+        switch (event.get_gesture_phase()) {
+        case Clutter.TouchpadGesturePhase.BEGIN:
+            this.emit('begin', time, x, y);
+            break;
+
+        case Clutter.TouchpadGesturePhase.UPDATE:
+            if (this._touchpadSettings.get_boolean('natural-scroll'))
+                delta = -delta;
+
+            this.emit('update', time, delta * SWIPE_MULTIPLIER);
+            break;
+
+        case Clutter.TouchpadGesturePhase.END:
+        case Clutter.TouchpadGesturePhase.CANCEL:
+            this.emit('end', time);
+            break;
+        }
+
+        return Clutter.EVENT_STOP;
+    }
+
+    setOrientation(orientation) {
+        this._orientation = orientation;
+    }
+};
+Signals.addSignalMethods(TouchpadSwipeGesture.prototype);
+
+var TouchSwipeGesture = GObject.registerClass({
+    Signals: { 'begin':  { param_types: [GObject.TYPE_UINT, GObject.TYPE_DOUBLE, GObject.TYPE_DOUBLE] },
+               'update': { param_types: [GObject.TYPE_UINT, GObject.TYPE_DOUBLE] },
+               'end':    { param_types: [GObject.TYPE_UINT] },
+               'cancel': { param_types: [GObject.TYPE_UINT] } },
+}, class TouchSwipeGesture extends Clutter.GestureAction {
+    _init(shouldSkip, nTouchPoints, thresholdTriggerEdge) {
+        super._init();
+        this.set_n_touch_points(nTouchPoints);
+        this.set_threshold_trigger_edge(thresholdTriggerEdge);
+
+        this._shouldSkip = shouldSkip;
+        this._distance = global.screen_height;
+        this._orientation = Clutter.Orientation.VERTICAL;
+
+        if (nTouchPoints > 1) {
+            global.display.connect('grab-op-begin', () => {
+                this.cancel();
+            });
+        }
+
+        this._lastPosition = 0;
+    }
+
+    vfunc_gesture_prepare(actor) {
+        if (!super.vfunc_gesture_prepare(actor))
+            return false;
+
+        if (this._shouldSkip())
+            return false;
+
+        let time = this.get_last_event(0).get_time();
+        let [xPress, yPress] = this.get_press_coords(0);
+        let [x, y] = this.get_motion_coords(0);
+
+        this._lastPosition =
+            this._orientation == Clutter.Orientation.VERTICAL ? y : x;
+
+        this.emit('begin', time, xPress, yPress);
+        return true;
+    }
+
+    // TODO: track center of the gesture instead of the first one
+    vfunc_gesture_progress(_actor) {
+        let [x, y] = this.get_motion_coords(0);
+        let pos = this._orientation == Clutter.Orientation.VERTICAL ? y : x;
+
+        let delta = pos - this._lastPosition;
+        this._lastPosition = pos;
+
+        let time = this.get_last_event(0).get_time();
+
+        this.emit('update', time, -delta / this._distance);
+
+        return true;
+    }
+
+    vfunc_gesture_end(_actor) {
+        let time = this.get_last_event(0).get_time();
+
+        this.emit('end', time);
+    }
+
+    vfunc_gesture_cancel(_actor) {
+        let time = Clutter.get_current_event_time();
+
+        this.emit('cancel', time);
+    }
+
+    setDistance(distance) {
+        this._distance = distance;
+    }
+
+    setOrientation(orientation) {
+        this._orientation = orientation;
+    }
+});
+
+var ScrollGesture = class ScrollGesture {
+    constructor(actor, shouldSkip) {
+        this._shouldSkip = shouldSkip;
+        this._began = false;
+        this._orientation = Clutter.Orientation.VERTICAL;
+
+        actor.connect('scroll-event', this._handleEvent.bind(this));
+    }
+
+    canHandleEvent(event) {
+        if (event.type() != Clutter.EventType.SCROLL)
+            return false;
+
+        if (event.get_scroll_source() != Clutter.ScrollSource.FINGER &&
+            event.get_source_device().get_device_type() != Clutter.InputDeviceType.TOUCHPAD_DEVICE)
+            return false;
+
+        if (this._shouldSkip())
+            return false;
+
+        return true;
+    }
+
+    _handleEvent(_actor, event) {
+        if (!this.canHandleEvent(event))
+            return Clutter.EVENT_PROPAGATE;
+
+        if (event.get_scroll_direction() != Clutter.ScrollDirection.SMOOTH)
+            return false;
+
+        if (this._shouldSkip())
+            return Clutter.EVENT_PROPAGATE;
+
+        let time = event.get_time();
+        let [dx, dy] = event.get_scroll_delta();
+        if (dx == 0 && dy == 0) {
+            this.emit('end', time);
+            this._began = false;
+            return Clutter.EVENT_STOP;
+        }
+
+        if (!this._began) {
+            let [x, y] = event.get_coords();
+            this.emit('begin', time, x, y);
+            this._began = true;
+        }
+
+        let delta;
+        if (this._orientation == Clutter.Orientation.VERTICAL)
+            delta = dy / TOUCHPAD_BASE_DISTANCE_V;
+        else
+            delta = dx / TOUCHPAD_BASE_DISTANCE_H;
+
+        this.emit('update', time, delta * SCROLL_MULTIPLIER);
+
+        return Clutter.EVENT_STOP;
+    }
+
+    setOrientation(orientation) {
+        this._orientation = orientation;
+    }
+};
+Signals.addSignalMethods(ScrollGesture.prototype);
+
+// USAGE:
+//
+// To correctly implement the gesture, there must be handlers for the following
+// signals:
+//
+// begin(tracker, monitor)
+//   The handler should check whether a deceleration animation is currently
+//   running. If it is, it should stop the animation (without resetting
+//   progress). Then it should call:
+//   tracker.confirmSwipe(distance, snapPoints, currentProgress, cancelProgress)
+//   If it's not called, the swipe would be ignored.
+//   The parameters are:
+//    * distance: the page size;
+//    * snapPoints: an (sorted with ascending order) array of snap points;
+//    * currentProgress: the current progress;
+//    * cancelprogress: a non-transient value that would be used if the gesture
+//      is cancelled.
+//   If no animation was running, currentProgress and cancelProgress should be
+//   same. The handler may set 'orientation' property here.
+//
+// update(tracker, progress)
+//   The handler should set the progress to the given value.
+//
+// end(tracker, duration, endProgress)
+//   The handler should animate the progress to endProgress. If endProgress is
+//   0, it should do nothing after the animation, otherwise it should change the
+//   state, e.g. change the current page or switch workspace.
+//   NOTE: duration can be 0 in some cases, in this case it should finish
+//   instantly.
+
+var SwipeTracker = class {
+    constructor(actor, allowedModes, allowDrag = true, allowScroll = true) {
+        this._allowedModes = allowedModes;
+        this._enabled = true;
+        this._orientation = Clutter.Orientation.VERTICAL;
+
+        this._reset();
+
+        let shouldSkip = () =>
+            (this._allowedModes & Main.actionMode) == 0 || !this._enabled;
+
+        this._touchpadGesture = new TouchpadSwipeGesture(shouldSkip);
+        this._touchpadGesture.connect('begin', this._beginGesture.bind(this));
+        this._touchpadGesture.connect('update', this._updateGesture.bind(this));
+        this._touchpadGesture.connect('end', this._endGesture.bind(this));
+
+        this._touchGesture = new TouchSwipeGesture(shouldSkip, 4,
+            Clutter.GestureTriggerEdge.NONE);
+        this._touchGesture.connect('begin', this._beginTouchSwipe.bind(this));
+        this._touchGesture.connect('update', this._updateGesture.bind(this));
+        this._touchGesture.connect('end', this._endGesture.bind(this));
+        this._touchGesture.connect('cancel', this._cancelGesture.bind(this));
+        global.stage.add_action(this._touchGesture);
+
+        if (allowDrag) {
+            this._dragGesture = new TouchSwipeGesture(shouldSkip, 1,
+                Clutter.GestureTriggerEdge.AFTER);
+            this._dragGesture.connect('begin', this._beginGesture.bind(this));
+            this._dragGesture.connect('update', this._updateGesture.bind(this));
+            this._dragGesture.connect('end', this._endGesture.bind(this));
+            this._dragGesture.connect('cancel', this._cancelGesture.bind(this));
+            actor.add_action(this._dragGesture);
+        } else {
+            this._dragGesture = null;
+        }
+
+        if (allowScroll) {
+            this._scrollGesture = new ScrollGesture(actor, shouldSkip);
+            this._scrollGesture.connect('begin', this._beginGesture.bind(this));
+            this._scrollGesture.connect('update', this._updateGesture.bind(this));
+            this._scrollGesture.connect('end', this._endGesture.bind(this));
+        } else {
+            this._scrollGesture = null;
+        }
+    }
+
+    canHandleScrollEvent(event) {
+        if (!this.enabled || this._scrollGesture == null)
+            return false;
+
+        return this._scrollGesture.canHandleEvent(event);
+    }
+
+    get enabled() {
+        return this._enabled;
+    }
+
+    set enabled(enabled) {
+        if (this._enabled == enabled)
+            return;
+
+        this._enabled = enabled;
+        if (!enabled && this._state == State.SCROLLING)
+            this._cancel();
+    }
+
+    get orientation() {
+        return this._orientation;
+    }
+
+    set orientation(orientation) {
+        if (this._orientation == orientation)
+            return;
+
+        this._orientation = orientation;
+
+        this._touchpadGesture.setOrientation(orientation);
+        this._touchGesture.setOrientation(orientation);
+        if (this._dragGesture)
+            this._dragGesture.setOrientation(orientation);
+        if (this._scrollGesture)
+            this._scrollGesture.setOrientation(orientation);
+    }
+
+    _reset() {
+        this._state = State.NONE;
+
+        this._snapPoints = [];
+        this._distance = 0;
+        this._initialProgress = 0;
+        this._cancelProgress = 0;
+
+        this._prevOffset = 0;
+        this._progress = 0;
+
+        this._prevTime = 0;
+        this._velocity = 0;
+
+        this._cancelled = false;
+    }
+
+    _cancel() {
+        this.emit('end', 0, this._cancelProgress);
+        this._reset();
+    }
+
+    _beginTouchSwipe(gesture, time, x, y) {
+        if (this._dragGesture)
+            this._dragGesture.cancel();
+
+        this._beginGesture(gesture, time, x, y);
+    }
+
+    _beginGesture(_gesture, time, x, y) {
+        if (this._state == State.SCROLLING)
+            return;
+
+        this._prevTime = time;
+
+        let rect = new Meta.Rectangle({ x, y, width: 1, height: 1 });
+        let monitor = global.display.get_monitor_index_for_rect(rect);
+
+        this.emit('begin', monitor);
+    }
+
+    _updateGesture(_gesture, time, delta) {
+        if ((this._allowedModes & Main.actionMode) == 0 || !this._enabled)
+            return;
+
+        if (this._state != State.SCROLLING)
+            return;
+
+        if (this.orientation == Clutter.Orientation.HORIZONTAL &&
+            Clutter.get_default_text_direction() == Clutter.TextDirection.RTL)
+            delta = -delta;
+
+        this._progress += delta;
+
+        if (time != this._prevTime)
+            this._velocity = delta / (time - this._prevTime);
+
+        let firstPoint = this._snapPoints[0];
+        let lastPoint = this._snapPoints[this._snapPoints.length - 1];
+        this._progress = clamp(this._progress, firstPoint, lastPoint);
+        this._progress = clamp(this._progress, this._initialProgress - 1,
+            this._initialProgress + 1);
+
+        this.emit('update', this._progress);
+
+        this._prevTime = time;
+    }
+
+    _getClosestSnapPoints() {
+        let upper, lower;
+
+        for (let i = 0; i < this._snapPoints.length; i++) {
+            if (this._snapPoints[i] >= this._progress) {
+                upper = this._snapPoints[i];
+                break;
+            }
+        }
+
+        for (let i = this._snapPoints.length - 1; i >= 0; i--) {
+            if (this._snapPoints[i] <= this._progress) {
+                lower = this._snapPoints[i];
+                break;
+            }
+        }
+
+        return [upper, lower];
+    }
+
+    _getEndProgress() {
+        if (this._cancelled)
+            return this._cancelProgress;
+
+        let [upper, lower] = this._getClosestSnapPoints();
+        let middle = (upper + lower) / 2;
+
+        if (this._progress > middle) {
+            return this._velocity * this._distance > -VELOCITY_THRESHOLD ||
+                   this._initialProgress > upper ? upper : lower;
+        } else {
+            return this._velocity * this._distance < VELOCITY_THRESHOLD ||
+                   this._initialProgress < lower ? lower : upper;
+        }
+    }
+
+    _endGesture(_gesture, _time) {
+        if ((this._allowedModes & Main.actionMode) == 0 || !this._enabled) {
+            // this._cancel();
+            return;
+        }
+
+        if (this._state != State.SCROLLING)
+            return;
+
+        let endProgress = this._getEndProgress();
+
+        let velocity = ANIMATION_BASE_VELOCITY;
+        if ((endProgress - this._progress) * this._velocity > 0)
+            velocity = this._velocity;
+
+        let duration = Math.abs((this._progress - endProgress) / velocity *
+            DURATION_MULTIPLIER);
+        if (duration > 0)
+            duration = clamp(duration, MIN_ANIMATION_DURATION,
+                MAX_ANIMATION_DURATION);
+
+        this.emit('end', duration, endProgress);
+        this._reset();
+    }
+
+    _cancelGesture(gesture, time) {
+        if (this._state != State.SCROLLING)
+            return;
+
+        this._cancelled = true;
+        this._endGesture(gesture, time);
+    }
+
+    confirmSwipe(distance, snapPoints, currentProgress, cancelProgress) {
+        this._distance = distance;
+        this._snapPoints = snapPoints;
+        this._initialProgress = currentProgress;
+        this._progress = currentProgress;
+        this._cancelProgress = cancelProgress;
+
+        this._touchGesture.setDistance(distance);
+        if (this._dragGesture)
+            this._dragGesture.setDistance(distance);
+
+        this._velocity = 0;
+        this._state = State.SCROLLING;
+    }
+};
+Signals.addSignalMethods(SwipeTracker.prototype);