[Web] Fix focal and anchor points coordinates (#4061)

## Description

Anchor and focal points were not converted to local view coordinates
before being sent. This PR fixes this problem.

Fixes #2929 

## Test plan

Tested on example from #3124

Author: m-bert

packages/react-native-gesture-handler/src/web/detectors/ScaleGestureDetector.ts

@@ -76,7 +76,7 @@ export default class ScaleGestureDetector implements ScaleGestureListener {
 
     const div: number = pointerUp ? numOfPointers - 1 : numOfPointers;
 
-    const coordsSum = tracker.getAbsoluteCoordsSum();
+    const coordsSum = tracker.getAbsoluteCoordsSum(ignoredPointer);
 
     const focusX = coordsSum.x / div;
     const focusY = coordsSum.y / div;

packages/react-native-gesture-handler/src/web/handlers/PinchGestureHandler.ts

@@ -70,9 +70,14 @@ export default class PinchGestureHandler extends GestureHandler {
   }
 
   protected override transformNativeEvent() {
+    const focal = this.delegate.absoluteToLocal(
+      this.scaleGestureDetector.focusX,
+      this.scaleGestureDetector.focusY
+    );
+
     return {
-      focalX: this.scaleGestureDetector.focusX,
-      focalY: this.scaleGestureDetector.focusY,
+      focalX: focal.x,
+      focalY: focal.y,
       velocity: this.velocity,
       scale: this.scale,
     };

packages/react-native-gesture-handler/src/web/handlers/RotationGestureHandler.ts

@@ -66,24 +66,25 @@ export default class RotationGestureHandler extends GestureHandler {
   }
 
   protected override transformNativeEvent() {
+    const anchor = this.getAnchor();
+
     return {
       rotation: this.rotation ? this.rotation : 0,
-      anchorX: this.getAnchorX(),
-      anchorY: this.getAnchorY(),
+      anchorX: anchor.x,
+      anchorY: anchor.y,
       velocity: this.velocity ? this.velocity : 0,
     };
   }
 
-  public getAnchorX(): number {
-    const anchorX = this.rotationGestureDetector.anchorX;
-
-    return anchorX ? anchorX : this.cachedAnchorX;
-  }
+  private getAnchor(): { x: number; y: number } {
+    const absX = this.rotationGestureDetector.anchorX;
+    const absY = this.rotationGestureDetector.anchorY;
 
-  public getAnchorY(): number {
-    const anchorY = this.rotationGestureDetector.anchorY;
+    if (Number.isFinite(absX) && Number.isFinite(absY)) {
+      return this.delegate.absoluteToLocal(absX, absY);
+    }
 
-    return anchorY ? anchorY : this.cachedAnchorY;
+    return { x: this.cachedAnchorX, y: this.cachedAnchorY };
   }
 
   protected override onPointerDown(event: AdaptedEvent): void {
@@ -104,12 +105,9 @@ export default class RotationGestureHandler extends GestureHandler {
       return;
     }
 
-    if (this.getAnchorX()) {
-      this.cachedAnchorX = this.getAnchorX();
-    }
-    if (this.getAnchorY()) {
-      this.cachedAnchorY = this.getAnchorY();
-    }
+    const anchor = this.getAnchor();
+    this.cachedAnchorX = anchor.x;
+    this.cachedAnchorY = anchor.y;
 
     this.tracker.track(event);
 
@@ -123,12 +121,9 @@ export default class RotationGestureHandler extends GestureHandler {
       return;
     }
 
-    if (this.getAnchorX()) {
-      this.cachedAnchorX = this.getAnchorX();
-    }
-    if (this.getAnchorY()) {
-      this.cachedAnchorY = this.getAnchorY();
-    }
+    const anchor = this.getAnchor();
+    this.cachedAnchorX = anchor.x;
+    this.cachedAnchorY = anchor.y;
 
     this.tracker.track(event);
 

packages/react-native-gesture-handler/src/web/tools/GestureHandlerDelegate.ts

@@ -13,6 +13,10 @@ export interface GestureHandlerDelegate<TComponent, THandler> {
   updateDOM(): void;
   isPointerInBounds({ x, y }: { x: number; y: number }): boolean;
   measureView(): MeasureResult;
+  absoluteToLocal(
+    absoluteX: number,
+    absoluteY: number
+  ): { x: number; y: number };
   reset(): void;
 
   onBegin(): void;

packages/react-native-gesture-handler/src/web/tools/GestureHandlerWebDelegate.ts

@@ -123,6 +123,46 @@ export class GestureHandlerWebDelegate
     };
   }
 
+  absoluteToLocal(
+    absoluteX: number,
+    absoluteY: number
+  ): { x: number; y: number } {
+    if (!this.view) {
+      throw new Error(tagMessage('Cannot convert coords on a null view'));
+    }
+
+    const rect = getEffectiveBoundingRect(this.view);
+    const transform = getComputedStyle(this.view).transform;
+    const matrix =
+      transform && transform !== 'none'
+        ? new DOMMatrix(transform)
+        : new DOMMatrix();
+
+    // Zero out translation — it's already reflected in the bounding rect
+    // center, so we only need to invert the rotation+scale part.
+    matrix.e = 0;
+    matrix.f = 0;
+    const inverse = matrix.inverse();
+
+    // Offset from the visual center of the bounding rect
+    const rectCenterX = rect.left + rect.width / 2;
+    const rectCenterY = rect.top + rect.height / 2;
+    const dx = absoluteX - rectCenterX;
+    const dy = absoluteY - rectCenterY;
+
+    // Apply inverse rotation+scale to get local-space offset from center
+    const localOffset = inverse.transformPoint(new DOMPoint(dx, dy));
+
+    // Add back the local center (untransformed dimensions)
+    const localCenterX = this.view.offsetWidth / 2;
+    const localCenterY = this.view.offsetHeight / 2;
+
+    return {
+      x: localCenterX + localOffset.x,
+      y: localCenterY + localOffset.y,
+    };
+  }
+
   reset(): void {
     this.eventManagers.forEach((manager: EventManager<unknown>) =>
       manager.resetManager()