FIX - preserve Home Screen drag across pages

frontend/src/utils/springboardDrag.test.ts

@@ -7,6 +7,8 @@ import {
   springboardEdgeDirection,
   springboardPageDragCompensation,
   springboardSwipeIntent,
+  springboardViewportDeltaToLocal,
+  springboardViewportToLocal,
 } from '@/utils/springboardDrag'
 
 describe('springboard widget drag', () => {
@@ -57,4 +59,16 @@ describe('springboard widget drag', () => {
     expect(springboardPageDragCompensation(2, 3, 368)).toBe(368)
     expect(springboardPageDragCompensation(2, 2, 368)).toBe(0)
   })
+
+  it('converts viewport coordinates into local phone coordinates under zoom', () => {
+    expect(
+      springboardViewportToLocal(169, 238, 100, 100, 253.92, 582.36, 368, 844),
+    ).toEqual({ x: 100, y: 200 })
+    expect(
+      springboardViewportToLocal(200, 250, 100, 50, 0, 0, 368, 844),
+    ).toEqual({ x: 100, y: 200 })
+    expect(
+      springboardViewportDeltaToLocal(69, 138, 253.92, 582.36, 368, 844),
+    ).toEqual({ x: 100, y: 200 })
+  })
 })

frontend/src/utils/springboardDrag.ts

@@ -11,6 +11,42 @@ export type SpringboardHomeEdgeTurn = SpringboardEdgeTurn & {
 
 export type SpringboardSwipeIntent = 'horizontal' | 'pending' | 'vertical'
 
+export type SpringboardLocalPoint = {
+  x: number
+  y: number
+}
+
+export function springboardViewportToLocal(
+  clientX: number,
+  clientY: number,
+  viewportLeft: number,
+  viewportTop: number,
+  viewportWidth: number,
+  viewportHeight: number,
+  layoutWidth: number,
+  layoutHeight: number,
+): SpringboardLocalPoint {
+  const scaleX = viewportWidth > 0 ? layoutWidth / viewportWidth : 1
+  const scaleY = viewportHeight > 0 ? layoutHeight / viewportHeight : 1
+  return {
+    x: (clientX - viewportLeft) * scaleX,
+    y: (clientY - viewportTop) * scaleY,
+  }
+}
+
+export function springboardViewportDeltaToLocal(
+  deltaX: number,
+  deltaY: number,
+  viewportWidth: number,
+  viewportHeight: number,
+  layoutWidth: number,
+  layoutHeight: number,
+): SpringboardLocalPoint {
+  const scaleX = viewportWidth > 0 ? layoutWidth / viewportWidth : 1
+  const scaleY = viewportHeight > 0 ? layoutHeight / viewportHeight : 1
+  return { x: deltaX * scaleX, y: deltaY * scaleY }
+}
+
 export function springboardPageDragCompensation(
   startPage: number,
   currentPage: number,