fix: 修复长文档分页与滚动同步

apps/web/src/scroll-sync.ts

@@ -0,0 +1,29 @@
+export interface ScrollMetrics {
+  scrollTop: number;
+  scrollHeight: number;
+  clientHeight: number;
+}
+
+function clamp(value: number, minimum: number, maximum: number) {
+  return Math.min(maximum, Math.max(minimum, value));
+}
+
+export function getScrollProgress(metrics: ScrollMetrics) {
+  const range = metrics.scrollHeight - metrics.clientHeight;
+  if (range <= 0) {
+    return 0;
+  }
+
+  return clamp(metrics.scrollTop / range, 0, 1);
+}
+
+export function getSyncedScrollTop(
+  source: ScrollMetrics,
+  target: ScrollMetrics
+) {
+  const targetRange = Math.max(
+    0,
+    target.scrollHeight - target.clientHeight
+  );
+  return getScrollProgress(source) * targetRange;
+}