Improve input form on snap example

Put the geometry type select input next to the 'draw' radio and select this
whenever the geometry type is changed.

examples/snap.js

@@ -94,18 +94,16 @@ const ExampleDraw = {
     source: vector.getSource(),
     type: 'Circle',
   }),
-  getActive: function () {
-    return this.activeType ? this[this.activeType].getActive() : false;
-  },
+  activeDraw: null,
   setActive: function (active) {
-    const type = optionsForm.elements['draw-type'].value;
+    if (this.activeDraw) {
+      this.activeDraw.setActive(false);
+      this.activeDraw = null;
+    }
     if (active) {
-      this.activeType && this[this.activeType].setActive(false);
-      this[type].setActive(true);
-      this.activeType = type;
-    } else {
-      this.activeType && this[this.activeType].setActive(false);
-      this.activeType = null;
+      const type = optionsForm.elements['draw-type'].value;
+      this.activeDraw = this[type];
+      this.activeDraw.setActive(true);
     }
   },
 };
@@ -117,14 +115,16 @@ ExampleDraw.init();
  */
 optionsForm.onchange = function (e) {
   const type = e.target.getAttribute('name');
-  const value = e.target.value;
   if (type == 'draw-type') {
-    ExampleDraw.getActive() && ExampleDraw.setActive(true);
+    ExampleModify.setActive(false);
+    ExampleDraw.setActive(true);
+    optionsForm.elements['interaction'].value = 'draw';
   } else if (type == 'interaction') {
-    if (value == 'modify') {
+    const interactionType = e.target.value;
+    if (interactionType == 'modify') {
       ExampleDraw.setActive(false);
       ExampleModify.setActive(true);
-    } else if (value == 'draw') {
+    } else if (interactionType == 'draw') {
       ExampleDraw.setActive(true);
       ExampleModify.setActive(false);
     }