refactor(server): canonicalize service API (#31049)

packages/tui/src/util/layout.ts

@@ -0,0 +1,25 @@
+import type { BaseRenderable, BoxRenderable } from "@opentui/core"
+
+const previousByParent = new WeakMap<
+  BaseRenderable,
+  { frameID: number; previous: WeakMap<BaseRenderable, BaseRenderable | undefined> }
+>()
+
+export function setPreLayoutSiblingMargin(el: BoxRenderable, margin: (previous?: BaseRenderable) => number) {
+  // Run before Yoga layout so scroll geometry matches the rendered frame.
+  el.onLifecyclePass = () => {
+    const parent = el.parent
+    if (!parent) return
+    const cached = previousByParent.get(parent)
+    const previous = cached?.frameID === el.ctx.frameId ? cached.previous : previousSiblings(parent, el.ctx.frameId)
+    const value = margin(previous.get(el))
+    if (el.marginTop !== value) el.marginTop = value
+  }
+}
+
+function previousSiblings(parent: BaseRenderable, frameID: number) {
+  const previous = new WeakMap<BaseRenderable, BaseRenderable | undefined>()
+  parent.getChildren().forEach((child, index, children) => previous.set(child, children[index - 1]))
+  previousByParent.set(parent, { frameID, previous })
+  return previous
+}