Halve the zoom speed and step in Trajectory Viewer v2.

src/app/data_types_internal.ts

@@ -390,17 +390,21 @@ export interface ZoomConfig {
   max: number;
   /** Buttons should increment or decrement by what magnitude. Default: .05 */
   step: number;
+  /** Increment or decrement per scroll / trackpad delta. Default: .02 */
+  scrollStepPerDelta?: number;
 }
+
+/** Increment or decrement per scroll / trackpad delta. */
+export const SCROLL_STEP_PER_DELTA = .02;
+
 /** Default zoom config that can be used for DAG Toolbar or DAG Renderer */
 export const defaultZoomConfig: ZoomConfig = {
   max: 1.5,
   min: .2,
   step: .10,
+  scrollStepPerDelta: SCROLL_STEP_PER_DELTA,
 };
 
-/** Increment or decrement per scroll / trackpad delta. */
-export const SCROLL_STEP_PER_DELTA = .02;
-
 /**
  * Allows you to construct a full DAG Zoom Config set from partial entries
  * which override the defaults

src/app/zooming_layer.directive.ts

@@ -144,13 +144,13 @@ export class ZoomingLayer implements OnInit, OnDestroy {
   }
 
   private zoomOnWheel($e: WheelEvent) {
-    const {min, max} = this.zoomStepConfig;
+    const {min, max, step, scrollStepPerDelta = SCROLL_STEP_PER_DELTA} = this.zoomStepConfig;
     const invSign = $e.deltaY > 0 ? -1 : 1;
     let newZoom = this.stateService.zoom.value +
         invSign *
             Math.min(
-                SCROLL_STEP_PER_DELTA * Math.abs($e.deltaY),
-                this.zoomStepConfig.step);
+                scrollStepPerDelta * Math.abs($e.deltaY),
+                step);
     newZoom = clampVal(newZoom, min, max);
 
     const container = this.dagWrapper.nativeElement.getBoundingClientRect();