onZoom: Return focalPoint to correctly sync zoom and remove actualAmount which was meant to indicate which scale was actually zoomed in favor of concise code.

Author: valerianoceanflight

src/core.ts

@@ -78,21 +78,18 @@ export function zoom(chart: Chart, amount: ZoomAmount, transition: UpdateMode =
   const xEnabled = x !== 1
   const yEnabled = y !== 1
   const enabledScales = getEnabledScalesByPoint(zoomOptions, focalPoint, chart)
-  const actualAmount = { x: 1, y: 1 }
 
   for (const scale of enabledScales) {
     if (scale.isHorizontal() && xEnabled) {
-      actualAmount.x = x
       doZoom(scale, x, focalPoint, limits)
     } else if (!scale.isHorizontal() && yEnabled) {
-      actualAmount.y = y
       doZoom(scale, y, focalPoint, limits)
     }
   }
 
   chart.update(transition)
 
-  zoomOptions?.onZoom?.({ chart, trigger, amount: actualAmount })
+  zoomOptions?.onZoom?.({ chart, trigger, amount: { x, y, focalPoint } })
 }
 
 export function zoomRect(

src/options.ts

@@ -121,7 +121,7 @@ export interface ZoomOptions {
   /**
    * Function called while the user is zooming
    */
-  onZoom?: (context: { chart: Chart; trigger: ZoomTrigger; amount?: { x: number, y: number } }) => void
+  onZoom?: (context: { chart: Chart; trigger: ZoomTrigger; amount?: { x: number, y: number } & { focalPoint: Point } }) => void
 
   /**
    * Function called once zooming is completed