support following area tags

src/shared/utils/dom.js

@@ -5,4 +5,80 @@ const isContentEditable = (element) => {
   );
 };
 
-export { isContentEditable };
+const rectangleCoordsRect = (coords) => {
+  let [left, top, right, bottom] = coords.split(',').map(n => Number(n));
+  return { left, top, right, bottom };
+};
+
+const circleCoordsRect = (coords) => {
+  let [x, y, r] = coords.split(',').map(n => Number(n));
+  return {
+    left: x - r,
+    top: y - r,
+    right: x + r,
+    bottom: y + r,
+  };
+};
+
+const polygonCoordsRect = (coords) => {
+  let params = coords.split(',');
+  let minx = Number(params[0]),
+    maxx = Number(params[0]),
+    miny = Number(params[1]),
+    maxy = Number(params[1]);
+  let len = Math.floor(params.length / 2);
+  for (let i = 2; i < len; i += 2) {
+    let x = Number(params[i]),
+      y = Number(params[i + 1]);
+    if (x < minx) {
+      minx = x;
+    }
+    if (x > maxx) {
+      maxx = x;
+    }
+    if (y < miny) {
+      miny = y;
+    }
+    if (y > maxy) {
+      maxy = y;
+    }
+  }
+  return { left: minx, top: miny, right: maxx, bottom: maxy };
+};
+
+const viewportRect = (e) => {
+  if (e.tagName !== 'AREA') {
+    return e.getBoundingClientRect();
+  }
+
+  let mapElement = e.parentNode;
+  let imgElement = document.querySelector(`img[usemap="#${mapElement.name}"]`);
+  let {
+    left: mapLeft,
+    top: mapTop
+  } = imgElement.getBoundingClientRect();
+  let coords = e.getAttribute('coords');
+  let rect = { left: 0, top: 0, right: 0, bottom: 0 };
+  switch (e.getAttribute('shape')) {
+  case 'rect':
+  case 'rectangle':
+    rect = rectangleCoordsRect(coords);
+    break;
+  case 'circ':
+  case 'circle':
+    rect = circleCoordsRect(coords);
+    break;
+  case 'poly':
+  case 'polygon':
+    rect = polygonCoordsRect(coords);
+    break;
+  }
+  return {
+    left: rect.left + mapLeft,
+    top: rect.top + mapTop,
+    right: rect.right + mapLeft,
+    bottom: rect.bottom + mapTop,
+  };
+};
+
+export { isContentEditable, viewportRect };