Merged PR 368: Fix toolbar zoom

Fix toolbar zoom

src/Components/SVG/SVGReactPanZoom/ui-toolbar/toolbar.tsx

@@ -6,7 +6,7 @@ import {
   MagnifyingGlassPlusIcon
 } from '@heroicons/react/24/outline';
 import React from 'react';
-import { fromObject, scale, transform, translate } from 'transformation-matrix';
+import { applyToPoint, fromObject, inverse, scale, transform, translate } from 'transformation-matrix';
 
 import {
   fitToViewer,
@@ -51,6 +51,38 @@ function set(value: Value, patch: object, action = null): Value {
   return Object.freeze(value);
 }
 
+/**
+ * Export x,y coords relative to SVG
+ * @param value
+ * @param viewerX
+ * @param viewerY
+ * @returns {*|{x, y}|{x: number, y: number}}
+ */
+function getSVGPoint(value: Value, viewerX: number, viewerY: number): PointObjectNotation {
+  const matrix = fromObject(value);
+
+  const inverseMatrix = inverse(matrix);
+  return applyToPoint(inverseMatrix, { x: viewerX, y: viewerY });
+}
+
+export function zoom(
+  value: Value,
+  SVGPointX: number,
+  SVGPointY: number,
+  scaleFactor: number
+): Value {
+  const matrix = transform(
+    fromObject(value),
+    translate(SVGPointX, SVGPointY),
+    scale(scaleFactor, scaleFactor),
+    translate(-SVGPointX, -SVGPointY)
+  );
+
+  return set(value, {
+    ...matrix
+  });
+}
+
 export function Toolbar({
   tool,
   value,
@@ -72,16 +104,8 @@ export function Toolbar({
     let fittedValue: Value = fitToViewer(value, SVGAlignX, SVGAlignY);
     if (fittingScale !== undefined) {
       const { viewerWidth, viewerHeight } = fittedValue;
-      const matrix = transform(
-        fromObject(fittedValue),
-        translate(viewerWidth, viewerHeight),
-        scale(fittingScale, fittingScale),
-        translate(-viewerWidth, -viewerHeight)
-      );
-
-      fittedValue = set(fittedValue, {
-        ...matrix
-      });
+      const SVGPoint = getSVGPoint(value, viewerWidth / 2, viewerHeight / 2);
+      fittedValue = zoom(fittedValue, SVGPoint.x, SVGPoint.y, fittingScale);
     }
 
     onChangeValue(fittedValue);