refactor: packages/

1 files changed, 35 insertions, 0 deletions

diff --git a/packages/excalidraw/scene/zoom.ts b/packages/excalidraw/scene/zoom.ts
new file mode 100644
index 0000000..5decf11
--- /dev/null
+++ b/packages/excalidraw/scene/zoom.ts
@@ -0,0 +1,35 @@
+import type { AppState, NormalizedZoomValue } from "../types";
+
+export const getStateForZoom = (
+  {
+    viewportX,
+    viewportY,
+    nextZoom,
+  }: {
+    viewportX: number;
+    viewportY: number;
+    nextZoom: NormalizedZoomValue;
+  },
+  appState: AppState,
+) => {
+  const appLayerX = viewportX - appState.offsetLeft;
+  const appLayerY = viewportY - appState.offsetTop;
+
+  const currentZoom = appState.zoom.value;
+
+  // get original scroll position without zoom
+  const baseScrollX = appState.scrollX + (appLayerX - appLayerX / currentZoom);
+  const baseScrollY = appState.scrollY + (appLayerY - appLayerY / currentZoom);
+
+  // get scroll offsets for target zoom level
+  const zoomOffsetScrollX = -(appLayerX - appLayerX / nextZoom);
+  const zoomOffsetScrollY = -(appLayerY - appLayerY / nextZoom);
+
+  return {
+    scrollX: baseScrollX + zoomOffsetScrollX,
+    scrollY: baseScrollY + zoomOffsetScrollY,
+    zoom: {
+      value: nextZoom,
+    },
+  };
+};