auto: 2026-07-28 18:28 (EOMSANGDON-HOME)

B04_wf1_Surface/B04_wf1_Surface_UI_MapViewer.ts

@@ -381,7 +381,17 @@ export function createSurfaceMapViewer(): SurfaceMapViewer {
     "wheel",
     (event) => {
       event.preventDefault();
+      const prevScale = scale;
       scale = Math.min(8, Math.max(0.5, scale * (event.deltaY < 0 ? 1.15 : 0.87)));
+      // 마우스 커서 아래 지점이 줌 전후로 같은 화면 위치에 머물도록 offset 보정.
+      // screen = center + (base - center)·scale + offset 이므로,
+      // 커서 고정 조건을 풀면 offset' = (cursor - center)·(1 - r) + offset·r (r = scale'/scale).
+      const ratio = scale / prevScale;
+      const rect = viewport.getBoundingClientRect();
+      const cursorX = event.clientX - rect.left - rect.width / 2;
+      const cursorY = event.clientY - rect.top - rect.height / 2;
+      offsetX = cursorX * (1 - ratio) + offsetX * ratio;
+      offsetY = cursorY * (1 - ratio) + offsetY * ratio;
       scheduleDraw();
     },
     { passive: false },