Merge pull request #656 from Conifer-Point/wiggle-room-for-touch-clicks

Add tolerance for touch clicks

src/GLViewer.ts

@@ -408,6 +408,24 @@ export class GLViewer {
         }
     };
 
+    /**
+     * Determine if a positioned event is "close enough" to mouseStart to be considered a click.
+     * With a mouse, the position should be exact, but allow a slight delta for a touch interface.
+     * @param {Event} event
+     * @param {{ allowTolerance, tolerance: number }} options
+     */
+    private closeEnoughForClick(event, { allowTolerance=event.targetTouches, tolerance=5}={}) {
+        const x = this.getX(event);
+        const y = this.getY(event);
+        if (allowTolerance) {
+            const deltaX = Math.abs(x - this.mouseStartX);
+            const deltaY = Math.abs(y - this.mouseStartY);
+            return deltaX <= tolerance && deltaY <= tolerance;
+        } else {
+            return x === this.mouseStartX && y === this.mouseStartY;
+        }
+    }
+
     private calcTouchDistance(ev) { // distance between first two
         // fingers
         var xdiff = ev.targetTouches[0].pageX -
@@ -883,7 +901,7 @@ export class GLViewer {
         if (this.isDragging && this.scene) { //saw mousedown, haven't moved
             var x = this.getX(ev);
             var y = this.getY(ev);
-            if (x == this.mouseStartX && y == this.mouseStartY) {
+            if (this.closeEnoughForClick(ev)) {
                 var offset = this.canvasOffset();
                 var mouseX = ((x - offset.left) / this.WIDTH) * 2 - 1;
                 var mouseY = -((y - offset.top) / this.HEIGHT) * 2 + 1;