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Mohamed Boudra
bd5061e7bd
Two causes, both reproduced on a clone of a real long thinking-partner chat
(replies and thinking rows several screens tall, GFM tables).
1. The window lowered in e42771970 (initial 2 / batch 2 / window 5) holds only
two or three tall rows, so a fling outruns the mounted range and the viewport
crosses unmounted rows: 65 blank frames over a 4,152-frame traversal. Keep the
small initial render that bounds cold-open measurement, but refill a window of
10 in batches of 10: 0 blank frames over 4,347, p95 25 ms.
2. Scroll-to-bottom from deep history animated across every row in between,
which no finite window can mount in time: 9 blank frames (~150 ms) per jump.
Animate only when the current offset is within the bottom-side overscan,
otherwise jump instantly. Near-bottom jumps still animate. Web already does
not animate this jump.
Cold open on the same chat is unchanged (first content 569 -> 568 ms); the
deeper window costs first-scroll acknowledgement (2.58 -> 2.94 s in a debug
build).
35 lines
1.2 KiB
TypeScript
35 lines
1.2 KiB
TypeScript
import { describe, expect, it } from "vitest";
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import { shouldAnimateNativeScrollToBottom } from "./native-scroll-animation";
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describe("native scroll-to-bottom animation", () => {
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it("jumps across unmounted history instead of animating through blank rows", () => {
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expect(
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shouldAnimateNativeScrollToBottom({ offsetY: 60_000, viewportHeight: 600, windowSize: 10 }),
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).toBe(false);
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});
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it("keeps near-bottom movement eligible for animation", () => {
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expect(
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shouldAnimateNativeScrollToBottom({ offsetY: 300, viewportHeight: 600, windowSize: 10 }),
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).toBe(true);
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});
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it("bounds travel by the bottom-side overscan, not the whole window", () => {
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expect(
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shouldAnimateNativeScrollToBottom({ offsetY: 2700, viewportHeight: 600, windowSize: 10 }),
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).toBe(true);
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expect(
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shouldAnimateNativeScrollToBottom({ offsetY: 2701, viewportHeight: 600, windowSize: 10 }),
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).toBe(false);
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expect(
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shouldAnimateNativeScrollToBottom({ offsetY: 1500, viewportHeight: 600, windowSize: 5 }),
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).toBe(false);
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});
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it("does not animate before the viewport has been measured", () => {
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expect(
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shouldAnimateNativeScrollToBottom({ offsetY: 0, viewportHeight: 0, windowSize: 10 }),
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).toBe(false);
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});
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});
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