gestures.js

import Clutter from 'gi://Clutter';
import Gio from 'gi://Gio';
import GLib from 'gi://GLib';
import Meta from 'gi://Meta';
import Shell from 'gi://Shell';

import * as Main from 'resource:///org/gnome/shell/ui/main.js';

import { Patches, Settings, Tiling, Utils, Lib, Navigator } from './imports.js';
import { Easer } from './utils.js';

const DIRECTIONS = {
    Horizontal: true,
    Vertical: false,
};

let vy, time, vState, navigator, direction, signals;
// 1 is natural scrolling, -1 is unnatural
let natural = 1;
export let gliding = false; // exported

let touchpadSettings;
export function enable(extension) {
    signals = new Utils.Signals();
    // Touchpad swipes only works in Wayland
    if (!Meta.is_wayland_compositor())
        return;

    touchpadSettings = new Gio.Settings({
        schema_id: 'org.gnome.desktop.peripherals.touchpad',
    });

    // monitor gesture-enabled for changes
    const gsettings = extension.getSettings();
    signals.connect(gsettings, 'changed::gesture-enabled', () => {
        gestureEnabled() ? swipeTrackersEnable(false) : swipeTrackersEnable();
    });

    /**
     * Swipetrackers are reset by gnome during overview, once exits overview
     * ensure swipe trackers are reset.
     */
    signals.connect(Main.overview, 'hidden', () => {
        if (gestureEnabled()) {
            swipeTrackersEnable(false);
        }
    });

    /**
       In order for the space.background actors to get any input we need to hide
       all the window actors from the stage.

       The stage takes care of scrolling vertically through the workspace mru.
       Delegating the horizontal scrolling to each space. This way vertical
       scrolling works anywhere, while horizontal scrolling is done on the space
       under the mouse cursor.
     */
    signals.connect(global.stage, 'captured-event', (actor, event) => {
        if (event.type() !== Clutter.EventType.TOUCHPAD_SWIPE) {
            return Clutter.EVENT_PROPAGATE;
        }

        const fingers = event.get_touchpad_gesture_finger_count();
        if (
            fingers <= 2 ||
            (Main.actionMode & Shell.ActionMode.OVERVIEW) > 0
        ) {
            return Clutter.EVENT_PROPAGATE;
        }

        const enabled = gestureEnabled();
        if (!enabled) {
            // switch to default swipe trackers
            swipeTrackersEnable();
        }

        const phase = event.get_gesture_phase();
        const [dx, dy] = event.get_gesture_motion_delta();
        switch (phase) {
        case Clutter.TouchpadGesturePhase.BEGIN:
            if (shouldPropagate(fingers)) {
                return Clutter.EVENT_PROPAGATE;
            }

            // PaperWM behaviour
            time = event.get_time();
            natural = touchpadSettings.get_boolean("natural-scroll") ? 1 : -1;
            direction = undefined;
            navigator = Navigator.getNavigator();
            navigator.connect('destroy', () => {
                vState = -1;
            });
            return Clutter.EVENT_STOP;
        case Clutter.TouchpadGesturePhase.UPDATE:
            if (shouldPropagate(fingers)) {
                return Clutter.EVENT_PROPAGATE;
            }

            if (direction === DIRECTIONS.Horizontal) {
                return Clutter.EVENT_PROPAGATE;
            }

            if (enabled && direction === undefined) {
                if (Math.abs(dx) < Math.abs(dy)) {
                    vy = 0;
                    vState = phase;
                    direction = DIRECTIONS.Vertical;
                }
            }
            if (enabled && direction === DIRECTIONS.Vertical) {
                // if in overview => propagate event to overview
                if (Main.overview.visible) {
                    return Clutter.EVENT_PROPAGATE;
                }

                let dir_y = -dy * natural * Settings.prefs.swipe_sensitivity[1];
                // if not Tiling.inPreview and swipe is UP => propagate event to overview
                if (!Tiling.inPreview && dir_y > 0) {
                    // enable swipe trackers which enables 3-finger up overview
                    swipeTrackersEnable();
                    return Clutter.EVENT_PROPAGATE;
                }

                if (gestureWorkspaceFingers() !== fingers) {
                    return Clutter.EVENT_PROPAGATE;
                }

                // initiates workspace stack switching
                swipeTrackersEnable(false);
                updateVertical(dir_y, event.get_time());
                return Clutter.EVENT_STOP;
            }
            return Clutter.EVENT_PROPAGATE;
        case Clutter.TouchpadGesturePhase.CANCEL:
        case Clutter.TouchpadGesturePhase.END:
            if (direction === DIRECTIONS.Vertical) {
                vState = phase;
                endVertical();
                return Clutter.EVENT_STOP;
            }
        }
        return Clutter.EVENT_PROPAGATE;
    });
}

function shouldPropagate(fingers) {
    if (
        // gestures disabled ==> gnome default behaviour
        !gestureEnabled()
    ) {
        swipeTrackersEnable();
        return true;
    }
    else if (
        fingers === 3 && gestureHorizontalFingers() !== 3
    ) {
        swipeTrackersEnable();
        return true;
    }
    else if (
        // if gesure enabled AND finger 4 AND horizontal finger != 4
        fingers === 4 &&
        gestureHorizontalFingers() !== 4 &&
        gestureWorkspaceFingers() !== 4
    ) {
        return true;
    }
    else {
        return false;
    }
}

export function disable() {
    signals.destroy();
    signals = null;
    Utils.timeout_remove(endVerticalTimeout);
    endVerticalTimeout = null;
    touchpadSettings = null;
}

export function gestureEnabled() {
    return Settings.prefs.gesture_enabled;
}

export function gestureHorizontalFingers() {
    return Settings.prefs.gesture_horizontal_fingers;
}

export function gestureWorkspaceFingers() {
    return Settings.prefs.gesture_workspace_fingers;
}

/**
   Handle scrolling horizontally in a space. The handler is meant to be
   connected from each space.background and bound to the space.
 */
let start, dxs = [], dts = [];
export function horizontalScroll(space, _actor, event) {
    if (event.type() !== Clutter.EventType.TOUCHPAD_SWIPE) {
        return Clutter.EVENT_PROPAGATE;
    }

    const fingers = event.get_touchpad_gesture_finger_count();
    if (
        fingers <= 2 || gestureHorizontalFingers() !== fingers
    ) {
        return Clutter.EVENT_PROPAGATE;
    }
    else if (
        /**
         * If gestures are disabled AND doing a 3-finger swipe (gnome default)
         * AND horizontal fingers are set to 3, then propagate.
         */
        !gestureEnabled() && fingers === 3
    ) {
        return Clutter.EVENT_PROPAGATE;
    }

    const phase = event.get_gesture_phase();
    const [dx] = event.get_gesture_motion_delta();
    switch (phase) {
    case Clutter.TouchpadGesturePhase.UPDATE:
        if (direction === undefined) {
            space.vx = 0;
            dxs = [];
            dts = [];
            space.hState = phase;
            start = space.targetX;
            Easer.removeEase(space.cloneContainer);
            direction = DIRECTIONS.Horizontal;
        }
        return update(space, -dx * natural * Settings.prefs.swipe_sensitivity[0], event.get_time());
    case Clutter.TouchpadGesturePhase.CANCEL:
    case Clutter.TouchpadGesturePhase.END:
        space.hState = phase;
        done(space, event);
        dxs = [];
        dts = [];
        return Clutter.EVENT_STOP;
    }
}

/**
   Handle scrolling horizontally using a touchscreen. This handler is meant to
   be connected to the global Panel and recreated every time the active space
   is changed.
 */
let walk = 0;
let sdx = null;
export function horizontalTouchScroll(_actor, event) {
    const type = event.type();
    const [myx] = event.get_coords();

    switch (type) {
    case Clutter.EventType.TOUCH_BEGIN:
        this.vx = 0;
        dxs = [];
        dts = [];
        sdx = myx;
        walk = 0;
        start = this.targetX;
        this.hState = Clutter.TouchpadGesturePhase.UPDATE;
        Easer.removeEase(this.cloneContainer);
        navigator = Navigator.getNavigator();
        direction = DIRECTIONS.Horizontal;
        update(this, 0, event.get_time());
        return Clutter.EVENT_PROPAGATE;
    case Clutter.EventType.TOUCH_UPDATE: {
        let dx = 0;
        if (sdx !== null) {
            dx = myx - sdx;
        }
        sdx = myx;
        walk += Math.abs(dx);

        /**
         * Here, we ignore the friction setting and reduce the reported time
         * scale, because the distances involved on a touch screen would make
         * the flick motion as understood by the trackpad handler impractical.
         */
        update(this, -dx, event.get_time() * .75);
        return Clutter.EVENT_PROPAGATE;
    }
    case Clutter.EventType.TOUCH_CANCEL:
    case Clutter.EventType.TOUCH_END:
        done(this, event);
        dxs = [];
        dts = [];
        sdx = null;
        walk = 0;
        this.hState = Clutter.TouchpadGesturePhase.END;
        if (walk < 20)
            return Clutter.EVENT_PROPAGATE; // Don't steal non-swipe events
        else
            return Clutter.EVENT_STOP;
    }
}

export function update(space, dx, t) {
    dxs.push(dx);
    dts.push(t);

    space.cloneContainer.x -= dx;
    space.targetX = space.cloneContainer.x;

    // Check which target window will be selected if we release the swipe at this
    // moment
    dx = Lib.sum(dxs.slice(-3));
    let v = dx / (t - dts.slice(-3)[0]);
    if (Number.isFinite(v)) {
        space.vx = v;
    }

    let accel = Settings.prefs.swipe_friction[0] / 16; // px/ms^2
    accel = space.vx > 0 ? -accel : accel;
    let duration = -space.vx / accel;
    let d = space.vx * duration + .5 * accel * duration ** 2;
    let target = Math.round(space.targetX - d);

    space.targetX = target;
    const selected = findTargetWindow(space, start - space.targetX > 0);
    space.targetX = space.cloneContainer.x;
    Tiling.updateSelection(space, selected);
    space.selectedWindow = selected;
    space.emit('select');

    return Clutter.EVENT_STOP;
}

export function done(space) {
    if (!Number.isFinite(space.vx) || space.length === 0) {
        navigator.finish();
        space.hState = -1;
        return Clutter.EVENT_STOP;
    }

    let startGlide = space.targetX;

    // timetravel
    let accel = Settings.prefs.swipe_friction[0] / 16; // px/ms^2
    accel = space.vx > 0 ? -accel : accel;
    let t = -space.vx / accel;
    let d = space.vx * t + .5 * accel * t ** 2;
    let target = Math.round(space.targetX - d);

    let mode = Clutter.AnimationMode.EASE_OUT_QUAD;
    let first;
    let last;

    let full = space.cloneContainer.width > space.width;
    // Only snap to the edges if we started gliding when the viewport is fully covered
    let snap = !(space.targetX >= 0 ||
                 space.targetX + space.cloneContainer.width <= space.width);
    if ((snap && target > 0) ||
        (full && target > space.width * 2)) {
        // Snap to left edge
        first = space[0][0];
        target = 0;
        mode = Clutter.AnimationMode.EASE_OUT_BACK;
    } else if ((snap && target + space.cloneContainer.width < space.width) ||
               (full && target + space.cloneContainer.width < -space.width)) {
        // Snap to right edge
        last = space[space.length - 1][0];
        target = space.width - space.cloneContainer.width;
        mode = Clutter.AnimationMode.EASE_OUT_BACK;
    }

    // Adjust for target window
    let selected;
    space.targetX = Math.round(target);
    selected = last || first || findTargetWindow(space, start - target > 0 );
    delete selected.lastFrame; // Invalidate frame information
    let x = Tiling.ensuredX(selected, space);
    target = x - selected.clone.targetX;

    // Scale down travel time if we've cut down the discance to travel
    let newD = Math.abs(startGlide - target);
    if (newD < Math.abs(d))
        t *= Math.abs(newD / d);

    // Use a minimum duration if we've adjusted travel
    if (target !== space.targetX || mode === Clutter.AnimationMode.EASE_OUT_BACK) {
        t = Math.max(t, 200);
    }
    space.targetX = target;

    Tiling.updateSelection(space, selected);
    space.selectedWindow = selected;
    space.emit('select');
    gliding = true;
    Easer.addEase(space.cloneContainer, {
        x: space.targetX,
        duration: t,
        mode,
        onStopped: () => {
            gliding = false;
        },
        onComplete: () => {
            if (!Tiling.inPreview)
                Navigator.getNavigator().finish();
        },
    });
}

/**
 * Finds a target window given a space and direction (-1 is left, 1 is right)
 * @param {Tiling.Space} space
 * @param {Boolean} direction
 * @returns
 */
export function findTargetWindow(space, direction) {
    let selected = space.selectedWindow?.clone;
    if (!selected) {
        return;
    }

    if (selected.x + space.targetX >= 0 &&
          selected.x + selected.width + space.targetX <= space.width) {
        return selected.meta_window;
    }
    selected = selected && space.selectedWindow;
    let workArea = space.workArea();
    let min = workArea.x;

    let windows = space.getWindows().filter(w => {
        let  clone = w.clone;
        let x = clone.targetX + space.targetX;
        return !(x + clone.width < min ||
                 x > min + workArea.width);
    });
    if (!direction) // scroll left
        windows.reverse();
    let visible = windows.filter(w => {
        let clone = w.clone;
        let x = clone.targetX + space.targetX;
        return x >= 0 &&
            x + clone.width <= min + workArea.width;
    });
    if (visible.length > 0) {
        return visible[0];
    }

    if (windows.length === 0) {
        let first = space.getWindow(0, 0);
        let last = space.getWindow(space.length - 1, 0);
        if (direction) {
            return last;
        } else {
            return first;
        }
    }

    if (windows.length === 1)
        return windows[0];

    let closest = windows[0].clone;
    let next = windows[1].clone;
    let r1, r2;
    if (direction) { // ->
        r1 = Math.abs(closest.targetX + closest.width + space.targetX) / closest.width;
        r2 = Math.abs(next.targetX + space.targetX - space.width) / next.width;
    } else {
        r1 = Math.abs(closest.targetX + space.targetX - space.width) / closest.width;
        r2 = Math.abs(next.targetX + next.width + space.targetX) / next.width;
    }
    // Choose the window the most visible width (as a ratio)
    if (r1 > r2)
        return closest.meta_window;
    else
        return next.meta_window;
}

let transition = 'easeOutQuad';
export function updateVertical(dy, t) {
    // if here then initiate workspace stack (for tiling inPreview show)
    if (!Tiling.inPreview) {
        Tiling.spaces.initWorkspaceStack();
    }

    let selected = Tiling.spaces.selectedSpace;
    let monitor = navigator.monitor;
    let v = dy / (t - time);
    time = t;
    const StackPositions = Tiling.StackPositions;
    if (dy > 0 &&
        selected !== navigator.from &&
        (selected.actor.y - dy < StackPositions.up * monitor.height)
    ) {
        dy = 0;
        vy = 1;
        selected.actor.y = StackPositions.up * selected.height;
        Tiling.spaces.selectStackSpace(Meta.MotionDirection.UP, false, transition);
        selected = Tiling.spaces.selectedSpace;
        Easer.removeEase(selected.actor);
        Easer.addEase(selected.actor, {
            scale_x: 0.9, scale_y: 0.9, time:
                Settings.prefs.animation_time, transition,
        });
    } else if (dy < 0 &&
        (selected.actor.y - dy > StackPositions.down * monitor.height)) {
        dy = 0;
        vy = -1;
        selected.actor.y = StackPositions.down * selected.height;
        Tiling.spaces.selectStackSpace(Meta.MotionDirection.DOWN, false, transition);
        selected = Tiling.spaces.selectedSpace;
        Easer.removeEase(selected.actor);
        Easer.addEase(selected.actor, {
            scale_x: 0.9, scale_y: 0.9, time:
                Settings.prefs.animation_time, transition,
        });
    } else if (Number.isFinite(v)) {
        vy = v;
    }

    selected.actor.y -= dy;
    if (selected === navigator.from) {
        let scale = 0.90;
        let s = 1 - (1 - scale) * (selected.actor.y / (0.1 * monitor.height));
        s = Math.max(s, scale);
        Easer.removeEase(selected.actor);
        selected.actor.set_scale(s, s);
    }
}

let endVerticalTimeout;
export function endVertical() {
    let test = vy > 0 ? () => vy < 0 : () => vy > 0;
    let glide = () => {
        if (vState < Clutter.TouchpadGesturePhase.END) {
            endVerticalTimeout = null;
            return false;
        }

        if (!Number.isFinite(vy)) {
            endVerticalTimeout = null;
            return false;
        }

        let selected = Tiling.spaces.selectedSpace;
        let y = selected.actor.y;
        if (selected === navigator.from && y <= 0.1 * selected.height) {
            navigator.finish();
            endVerticalTimeout = null;
            return false;
        }

        if (test()) {
            endVerticalTimeout = null;
            return false;
        }

        let dy = vy * 16;
        let v = vy;
        let accel = Settings.prefs.swipe_friction[1];
        accel = v > 0 ? -accel : accel;
        updateVertical(dy, time + 16);
        vy += accel;
        return true; // repeat
    };

    /**
     * The below timeout_add will be destroyed by the glide
     * function - which returns false (thus destroying this timeout)
     * when user gesture fininshes, a space is selected, etc.
     */
    endVerticalTimeout = GLib.timeout_add(GLib.PRIORITY_DEFAULT, 16, glide);
}

/**
 * Enables (or disables) gnome swipe trackers which take care of the
 * default 3 finger swipe actions.
 * @param {Boolean} option
 */
export function swipeTrackersEnable(option) {
    let enable = option ?? true;
    Patches.swipeTrackers.forEach(t => t.enabled = enable);
}