@thi.ng/rstream-gestures/gesture-stream.js

Unified mouse, mouse wheel & multi-touch event stream abstraction

import { isBoolean } from "@thi.ng/checks/is-boolean";
import { isNumber } from "@thi.ng/checks/is-number";
import { clamp } from "@thi.ng/math/interval";
import { fromDOMEvent } from "@thi.ng/rstream/event";
import { __nextID } from "@thi.ng/rstream/idgen";
import { merge } from "@thi.ng/rstream/merge";
import { map } from "@thi.ng/transducers/map";
const START_EVENTS = /* @__PURE__ */ new Set([
  "mousedown",
  "touchmove",
  "touchstart",
  "mousemove"
]);
const END_EVENTS = /* @__PURE__ */ new Set(["mouseup", "touchend", "touchcancel"]);
const BASE_EVENTS = ["mousemove", "mousedown", "touchstart", "wheel"];
const EVENT_GESTURETYPES = {
  touchstart: "start",
  touchmove: "drag",
  touchend: "end",
  touchcancel: "end",
  mousedown: "start",
  mouseup: "end",
  wheel: "zoom"
};
const gestureStream = (el, _opts) => {
  const opts = {
    zoom: 1,
    absZoom: true,
    minZoom: 0.25,
    maxZoom: 4,
    smooth: 1,
    eventOpts: { capture: true },
    preventDefault: true,
    preventScrollOnZoom: true,
    preventContextMenu: true,
    local: true,
    scale: false,
    ..._opts
  };
  opts.id = opts.id || `gestures-${__nextID()}`;
  const active = [];
  let zoom = clamp(
    isNumber(opts.zoom) ? opts.zoom : opts.zoom.deref() || 1,
    opts.minZoom,
    opts.maxZoom
  );
  let zoomDelta = 0;
  let numTouches = 0;
  let lastPos = [0, 0];
  let tempStreams;
  const isBody = el === document.body;
  const tempEvents = [
    "touchend",
    "touchcancel",
    "touchmove",
    "mouseup"
  ];
  !isBody && tempEvents.push("mousemove");
  opts.preventContextMenu && el.addEventListener("contextmenu", (e) => e.preventDefault());
  const gestureStart = (etype, events, bounds, isTouch) => {
    const isStart = etype === "mousedown" || etype === "touchstart";
    for (const t of events) {
      const id = t.identifier || 0;
      const pos = __getPos(t, bounds, opts.local, opts.scale);
      let touch = active.find((t2) => t2.id === id);
      if (!touch && isStart) {
        touch = { id, start: pos };
        active.push(touch);
        numTouches++;
      }
      if (touch) {
        touch.pos = pos;
        touch.delta = [
          pos[0] - touch.start[0],
          pos[1] - touch.start[1]
        ];
        if (isTouch) {
          touch.force = t.force;
        }
      }
    }
    if (isStart && !tempStreams) {
      tempStreams = tempEvents.map(
        (id) => __eventSource(document.body, id, opts, "-temp")
      );
      stream.addAll(tempStreams);
      !isBody && stream.removeID("mousemove");
    }
  };
  const gestureEnd = (events) => {
    for (const t of events) {
      const id = t.identifier || 0;
      const idx = active.findIndex((t2) => t2.id === id);
      if (idx !== -1) {
        active.splice(idx, 1);
        numTouches--;
      }
    }
    if (numTouches === 0) {
      stream.removeAll(tempStreams);
      !isBody && stream.add(__eventSource(el, "mousemove", opts));
      tempStreams = void 0;
    }
  };
  const updateZoom = (e) => {
    const zdelta = opts.smooth * ("wheelDeltaY" in e ? -e.wheelDeltaY / 120 : e.deltaY / 40);
    zoom = opts.absZoom ? clamp(zoom + zdelta, opts.minZoom, opts.maxZoom) : zdelta;
    zoomDelta = zdelta;
  };
  const stream = merge({
    id: opts.id,
    src: BASE_EVENTS.map((id) => __eventSource(el, id, opts)),
    xform: map((e) => {
      const etype = e.type;
      if (etype === "$zoom") {
        zoomDelta = e.value - zoom;
        if (opts.absZoom) {
          zoom = clamp(zoom + zoomDelta, opts.minZoom, opts.maxZoom);
        } else {
          zoom = zoomDelta;
        }
        return {
          pos: lastPos.slice(),
          buttons: 0,
          type: "zoom",
          active,
          zoom,
          zoomDelta,
          isTouch: false
        };
      }
      const type = __classifyEventType(etype, !!tempStreams);
      let isTouch = !!e.touches;
      let events = isTouch ? Array.from(e.changedTouches) : [e];
      const bounds = el.getBoundingClientRect();
      if (START_EVENTS.has(etype)) {
        gestureStart(etype, events, bounds, isTouch);
      } else if (END_EVENTS.has(etype)) {
        gestureEnd(events);
      } else if (type === "zoom") {
        updateZoom(e);
      }
      lastPos = __getPos(events[0], bounds, opts.local, opts.scale);
      opts.preventDefault && e.preventDefault();
      return {
        event: e,
        pos: lastPos,
        buttons: isTouch ? active.length : e.buttons,
        type,
        active,
        zoom,
        zoomDelta,
        isTouch
      };
    })
  });
  if (!isNumber(opts.zoom)) {
    stream.add(opts.zoom.map((x) => ({ type: "$zoom", value: x })));
  }
  return stream;
};
const __eventSource = (el, type, opts, suffix = "") => {
  let eventOpts = opts.eventOpts;
  if (type === "wheel" && opts.preventScrollOnZoom) {
    eventOpts = isBoolean(eventOpts) ? { capture: eventOpts, passive: false } : { ...eventOpts, passive: false };
  }
  return fromDOMEvent(el, type, eventOpts, { id: type + suffix });
};
const __classifyEventType = (etype, isActive) => etype === "mousemove" ? isActive ? "drag" : "move" : EVENT_GESTURETYPES[etype];
const __getPos = (e, bounds, isLocal, doScale) => {
  let x = e.clientX;
  let y = e.clientY;
  if (isLocal) {
    x -= bounds.left;
    y -= bounds.top;
  }
  if (doScale) {
    const dpr = window.devicePixelRatio || 1;
    x *= dpr;
    y *= dpr;
  }
  return [x | 0, y | 0];
};
export {
  gestureStream
};