gravity/simulator.js

import {
  DISPLAY_CURRENT_MODE,
  DISPLAY_CURRENT_SCALE,
  DISPLAY_PANNING_INFO,
  EVENT_ZOOM,
  SCALE_POWER_MAX,
  SCALE_POWER_MIN,
} from './config.js';
import { Display } from './display.js';
import { Objects } from './objects.js';
import { Overlay } from './overlay.js';
import { Pointer } from './pointer.js';
import { Options } from './options.js';
import { ModeSwitch } from './tool/modes.js';
import { OptionsTool } from './tool/options.js';
import { PlayPause } from './tool/play-pause.js';
import { Zoom } from './tool/zoom.js';
import { Toolbar } from './toolbar.js';
import { ToolbarGroup } from './toolbar-group.js';

export class Sim {
  info = {};
  rawTime = undefined;
  time = undefined;
  nextZoom = undefined;
  playing = true;

  objects = undefined;
  display = undefined;
  overlay = undefined;
  pointer = undefined;
  panning = undefined;
  toolbarGroups = {};
  toolbars = {};

  isCurrentMode = () => undefined;
  getCurrentMode = () => undefined;
  setCurrentMode = () => undefined;
  getOption = () => undefined;
  onModeEnter = () => undefined;
  onModeLeave = () => undefined;

  constructor(divId) {
    this.divId = divId;
    const div = document.getElementById(this.divId);
    this.div = div;

    this.options = new Options(this);
    this.display = new Display(this);
    this.objects = new Objects(this);
    this.toolbarGroups = {
      left: new ToolbarGroup(this),
      right: new ToolbarGroup(this).topRight(),
    };
    this.toolbars = {
      tools: new Toolbar(this, 'Tools', this.toolbarGroups.left),
      modes: new Toolbar(this, 'Modes', this.toolbarGroups.left),
      options: new Toolbar(this, 'Options', this.toolbarGroups.right),
      params: new Toolbar(this, 'Parameters', this.toolbarGroups.right),
    }
    this.overlay = new Overlay(this);
    this.pointer = new Pointer(this);

    {
      // Configure toolbars
      const { tools, modes, options, params } = this.toolbars;
      // Primary Toolbar
      tools.addTool(new Zoom(tools));
      tools.addTool(new PlayPause(tools));
      // Secondary Toolbar: Mode Switches
      modes.addTool(new ModeSwitch(modes));
      // Options Toolbar
      options.addTool(new OptionsTool(options, [
        'pauseDuring', 'display', 'collision'
      ]));
      // Parameters Toolbar
      params.addTool(new OptionsTool(params, [
        'param'
      ]));
    }

    // Initiate main loop
    this.rawTime = document.timeline.currentTime / 1000;
    this.time = 0;
    requestAnimationFrame(t => this.loop(t));
  }

  // It's better not to change the scale in the middle of possible frame calculations,
  // so use this to schedule it and let the event loop pick it up.
  // velocity should be in Sim coordinate scale
  scheduleZoom({x, y}, factor, velocity) {
    this.nextZoom = {x, y, factor, velocity};
  }

  // x, y should be in Sim coordinates
  // velocity should be in Sim coordinate scale
  zoom({x, y, factor, velocity}) {
    // x, y are the mouse coordinates, which should be the center of the new view frame
    // the new view origin should be x, y minus half the new view width and height
    // compute new scale
    this.display.scalePower += factor;
    // TODO: Lossy rescaling to expand zoom range
    if (this.display.scalePower > SCALE_POWER_MAX) this.display.scalePower = SCALE_POWER_MAX;
    if (this.display.scalePower < SCALE_POWER_MIN) this.display.scalePower = SCALE_POWER_MIN;
    // compute coordinates of new view frame
    this.display.viewOrigin.x = x - this.display.width / 2;
    this.display.viewOrigin.y = y - this.display.height / 2;

    this.pointer.clearPointerHistory();

    if (this.playing && velocity) {
      this.panning = {
        velocity: {
          x: -velocity.x,
          y: -velocity.y,
        }
      };
    }

    const e = new CustomEvent(EVENT_ZOOM);
    this.div.dispatchEvent(e);
  }

  // Transform display coordinates to simulator coordinates using scale and viewOrigin
  screenToSim(x, y) {
    return this.display.screenToSim(x, y);
  }

  play() {
    this.playing = true;
  }

  pause() {
    this.playing = false;
  }

  getScaleDisplay() {
    const scale = 2 ** Math.abs(this.display.scalePower);
    return this.display.scalePower >= 0 ? `${scale}` : `1/${scale}`;
  }

  // cb: () => undefined
  onZoom(cb) {
    this.div.addEventListener(EVENT_ZOOM, () => {
      cb();
    });
  }

  // Main loop
  loop(currentTime) {
    currentTime /= 1000;
    const timeScale = this.getOption('param.timeScale');
    const elapsedTime = (currentTime - this.rawTime) * timeScale;
    this.rawTime = currentTime;
    if (this.playing) {
      this.time += elapsedTime;
    }

    if (DISPLAY_CURRENT_MODE) {
      this.info['Mode'] = this.getCurrentMode();
    }

    if (this.nextZoom) {
      this.zoom(this.nextZoom);
      this.nextZoom = undefined;
    }

    if (DISPLAY_CURRENT_SCALE) {
      this.info['Scale'] = this.getScaleDisplay();
    }

    if (DISPLAY_PANNING_INFO) {
      const {x, y} = this.panning?.velocity ?? {};
      this.info['Panning'] = [`${x?.toPrecision(6)}, `, y?.toPrecision(6)];
    }

    this.display.computePanning(elapsedTime);
    this.objects.computeFrame(elapsedTime);
    this.overlay.renderInfo();
    this.display.fillCanvas();
    this.display.drawObjects();
    for (const group in this.toolbarGroups) {
      this.toolbarGroups[group].frame();
    }

    requestAnimationFrame(t => this.loop(t));
  }
}