allow moving object while creating it

simulator.js

@@ -96,14 +96,19 @@ export class Sim {
         this.info['Mouse move'] = [`${e.clientX}, `, `${e.clientY}`];
         this.renderInfo();
       }
+      this.handleCursorMove(e.clientX, e.clientY);
     });
+
     // Monitor touch events
     el.addEventListener('touchmove', e => {
       if (this.DISPLAY_CURSOR_INFO) {
         this.info['Touch move'] = [`${e.touches[0].pageX}, `, `${e.touches[0].pageY}`];
         this.renderInfo();
       }
+      // TODO: If e.touches.length > 1, user may be engaging pinch to zoom
+      this.handleCursorMove(e.touches[0].pageX, e.touches[0].pageY);
     });
+
     el.addEventListener('pointerdown', e => {
       if (this.DISPLAY_CURSOR_INFO) {
         this.info['Pointer down'] = [`${e.clientX}, `, `${e.clientY}`];
@@ -111,6 +116,7 @@ export class Sim {
       }
       this.createObject(e.clientX, e.clientY);
     });
+
     el.addEventListener('pointerup', e => {
       if (this.DISPLAY_CURSOR_INFO) {
         this.info['Pointer up'] = [`${e.clientX}, `, `${e.clientY}`];
@@ -118,6 +124,7 @@ export class Sim {
       }
       this.doneCreatingObject();
     });
+
     el.addEventListener('click', e => {
       if (this.DISPLAY_CURSOR_INFO) {
         this.info['Click'] = [`${e.clientX}, `, `${e.clientY}`];
@@ -130,6 +137,16 @@ export class Sim {
     requestAnimationFrame(t => this.loop(t));
   }
 
+  // Handle cursor (mouse or touch) movement
+  handleCursorMove(x, y) {
+    // If the cursor moves while creating an object, update the position of the object
+    if (this.creatingObject !== undefined) {
+      const obj = this.objects[this.creatingObject];
+      obj.position.x = x;
+      obj.position.y = y;
+    }
+  }
+
   // Create an object with mass that grows as pointer is held down
   createObject(x, y) {
     const obj = new MassObject(x, y);