WIP: Fix TouchEvent clientX bug

material-components · Feb 12, 2019 · a0cce8c · a0cce8c
1 parent 1e8b7e2
commit a0cce8c
Showing 1 changed file with 5 additions and 1 deletion.
diff --git a/packages/mdc-select/index.ts b/packages/mdc-select/index.ts
@@ -502,10 +502,14 @@ class MDCSelect extends MDCComponent<MDCSelectFoundation> implements RippleCapab
    */
   private getNormalizedXCoordinate_(evt: MouseEvent | TouchEvent): number {
     const targetClientRect = (evt.target as Element).getBoundingClientRect();
-    const xCoordinate = (evt as MouseEvent).clientX; // TODO(acdvorak): How does this work for TouchEvent?
+    const xCoordinate = this.isTouchEvent_(evt) ? evt.touches[0].clientX : evt.clientX;
     return xCoordinate - targetClientRect.left;
   }
 
+  private isTouchEvent_(evt: MouseEvent | TouchEvent): evt is TouchEvent {
+    return Boolean((evt as TouchEvent).touches);
+  }
+
   /**
    * Returns a map of all subcomponents to subfoundations.
    */