felt/static/map.js

let map = null;
let mapImg = null;
const tokens = [];
const worldBounds = [[180, -180], [-180, 180]];
const cameraBounds = [[270, -270], [-270, 270]];

function initializeMap(mapImgUrl) {
  let init = false;
  if (!map) {
    init = true;
    map = L.map("map", {
      minZoom: 0,
      maxZoom: 4,
      crs: L.CRS.Simple,
      attributionControl: false,
      zoomControl: false 
    });
    map.on("zoomend", () => {
      resizeMarkers();
      scaleSpritePreview();
      scaleAltSpritePreview();
    });
  }
  
  if (mapImg) {
    mapImg.removeFrom(map);
  }
  
  mapImg = L.imageOverlay(mapImgUrl, worldBounds);
  mapImg.addTo(map);
  map.setMaxBounds(cameraBounds);
  
  if (init) {
    map.setView([0,0], 2);
  }
  
  resizeMarkers();
}

// this works but assumes the map is square (reasonable limitation I think)
function resizeMarkers() {

  // for newly created tokens, the icon may not be loaded and thus the resize will not properly complete
  // TODO: we need a way to queue the resize for when the icon is finished loading

  tokens.forEach(t=>{
    const icon = t.m.options.icon;

    const scaleFactor = mapImg._image.clientWidth / mapImg._image.naturalWidth;
    
    icon.options.iconSize = [scaleFactor * t.t.w, scaleFactor * t.t.h];
    icon.options.iconAnchor = [scaleFactor * t.t.oX, scaleFactor * t.t.oY];
    icon.options.popupAnchor = [0, -scaleFactor * t.t.oY];
    
    t.m.setIcon(icon);
  });

}

function sortByTokenName(a, b) {
  return (a.t.name < b.t.name)
    ? -1
    : ((a.t.name > b.t.name)
      ? 1
      : 0)
}

function processTokens(tokenChanges) {
  for (const t of tokenChanges) {
    const i = tokens.findIndex(tk=>tk.t.id == t.id);
    if (i >= 0) {
      const self = tokens[i];
      // token was made active
      if (t.x != null && t.y != null && !self.t.active && t.active) {
        self.t.active = true;
        self.m.addTo(map);
      // token was made inactive
      } else if (t.x != null && t.y != null && self.t.active && !t.active) {
        self.t.active = false;
        self.m.removeFrom(map);
      // token was destroyed
      } else if (t.x == null && t.y == null) {
        self.m.removeFrom(map);
        tokens.splice(i, 1);
      // token was moved
      } else {
        self.t.x = t.x;
        self.t.y = t.y;
        self.m.setLatLng([t.y, t.x]);
      }
    } else {
      if (t.x != null && t.y != null) {
        const self = NewToken(t);
        tokens.push(self);
        tokens.sort(sortByTokenName);
        if (t.active) {
          self.m.addTo(map);
        }
      }
    }
  }
  resizeMarkers();
}

function toggleActive(tokenId) {
  const existing = tokens.find(t=>t.t.id == tokenId);
  if (existing) {
    const self = Object.assign({}, existing.t);
    self.active = !self.active;
    publish({token: stripToken(self)});
  }
}

function moveToken(id) {
  const existing = tokens.find(t=>t.t.id == id);
  if (existing) {
    const self = Object.assign({}, existing.t);
    const realPos = existing.m.getLatLng();
    self.x = realPos.lng;
    self.y = realPos.lat;
    publish({token: stripToken(self)});
  }
}

function stripToken(self) {
    delete self.sprite;
    delete self.name;
    delete self.w;
    delete self.h;
    delete self.oX;
    delete self.oY;
    return self;
}

function NewToken(token) {
  const marker = L.marker([token.y,token.x], {
    icon: L.icon({
      iconUrl: token.sprite,
      iconSize: [token.w,token.h],
      iconAnchor: [token.oX, token.oY],
      popupAnchor: [0, -token.oY]
    }),
    title: token.name,
    draggable: true,
    autoPan: true
  });
  
  marker.on("moveend", ()=>{moveToken(token.id)});
  
  const node = document.createElement('div');
  node.innerText = token.name;
  marker.bindPopup(node);

  return {
    t: token,
    m: marker,
  };
}