Yaowei Zheng
79 lines
3.7 KiB
TypeScript
79 lines
3.7 KiB
TypeScript
/**
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* Unit tests for stream-follow.ts (issue #75): in a short scroll area (scrollable
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* slack < 80px), scrolling up immediately exits auto-stick-to-bottom; staying at
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* a historical position, streaming increments don't override that intent; the
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* user can scroll back down to resume; content-shrink clamping isn't
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* misread as an upward scroll.
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*/
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import { describe, expect, it } from "vitest";
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import { createStreamFollow } from "../src/features/chat/stream-follow";
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/** Short scroll area: content 500px, viewport 460px, scrollable slack only 40px (always under the 80px threshold). */
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const SHORT = { scrollHeight: 500, clientHeight: 460 };
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describe("createStreamFollow", () => {
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it("short scroll area: wheel-up exits following immediately, even at the top (position no longer changes)", () => {
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const f = createStreamFollow();
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expect(f.stick).toBe(true);
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f.scrolled({ ...SHORT, scrollTop: 40 }); // scroll event from the program sticking to bottom: still following.
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expect(f.stick).toBe(true);
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f.wheel(-3);
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expect(f.stick).toBe(false);
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});
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it("short scroll area: scrollbar/keyboard up-moves (scrollTop decreasing) exit too", () => {
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const f = createStreamFollow();
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f.scrolled({ ...SHORT, scrollTop: 40 });
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f.scrolled({ ...SHORT, scrollTop: 20 }); // moved up, 20px from bottom (> the 1px clamp margin).
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expect(f.stick).toBe(false);
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});
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it("touch pull-down (finger moving down) exits; pushing up does not", () => {
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const f = createStreamFollow();
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f.touchStart(100);
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f.touchMove(90); // finger pushes up = content scrolls down, stays following.
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expect(f.stick).toBe(true);
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f.touchMove(120); // finger pulls down = content scrolls up, exits.
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expect(f.stick).toBe(false);
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f.touchEnd();
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});
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it("staying at a historical position: streaming increments (scrollTop unchanged, content taller) do not change the intent", () => {
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const f = createStreamFollow();
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f.scrolled({ ...SHORT, scrollTop: 40 });
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f.wheel(-3);
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f.scrolled({ ...SHORT, scrollTop: 0 }); // scrolled up to the top.
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expect(f.stick).toBe(false);
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// Content keeps growing while the user's position stays put: as long as scrollTop
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// doesn't change, following isn't mistakenly resumed.
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f.scrolled({ scrollHeight: 900, clientHeight: 460, scrollTop: 0 });
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expect(f.stick).toBe(false);
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});
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it("the user scrolling back near the bottom (within 80px) resumes following", () => {
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const f = createStreamFollow();
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f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 1540 });
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f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 800 }); // dragged up, exits.
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expect(f.stick).toBe(false);
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f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 1470 }); // back to 70px from bottom.
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expect(f.stick).toBe(true);
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});
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it("content shrink clamping scrollTop down (still at the bottom) does not count as scrolling up", () => {
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const f = createStreamFollow();
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f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 1540 }); // stuck to bottom, following.
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// Group collapse shrinks content height; the browser clamps scrollTop to the new
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// bottom: it moved up, but it's still 0px from the bottom.
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f.scrolled({ scrollHeight: 1500, clientHeight: 460, scrollTop: 1040 });
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expect(f.stick).toBe(true);
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});
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it("the first scroll event already at a historical position (≥ 80px from bottom): initialized as not following by position", () => {
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const f = createStreamFollow();
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// The first event has no direction to judge from (e.g. a restored scroll position),
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// and is 540px from the bottom: it shouldn't wait for a subsequent scroll-up to exit.
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f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 1000 });
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expect(f.stick).toBe(false);
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});
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});
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