97 lines
3.3 KiB
TypeScript
97 lines
3.3 KiB
TypeScript
import {
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easeToward,
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localAtProgress,
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locateInReel,
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REEL_HOLD,
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REEL_LAST_TAIL,
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reelHolds,
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reelStarts,
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videoProgress,
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} from "./showcase-math";
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describe("locateInReel", () => {
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const weights = [1, 2, 1];
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it("maps overall progress to a project and a position inside it", () => {
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expect(locateInReel(weights, 0)).toEqual({ index: 0, local: 0 });
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expect(locateInReel(weights, 0.125)).toEqual({ index: 0, local: 0.5 });
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const middle = locateInReel(weights, 0.5);
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expect(middle.index).toBe(1);
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expect(middle.local).toBeCloseTo(0.5);
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expect(locateInReel(weights, 1)).toEqual({ index: 2, local: 1 });
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});
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it("clamps progress outside the pinned range", () => {
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expect(locateInReel(weights, -3)).toEqual({ index: 0, local: 0 });
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expect(locateInReel(weights, 7)).toEqual({ index: 2, local: 1 });
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});
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it("copes with an empty reel", () => {
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expect(locateInReel([], 0.4)).toEqual({ index: 0, local: 0 });
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});
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it("gives each project the share of the scroll that its weight asks for", () => {
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expect(reelStarts(weights)).toEqual([0, 0.25, 0.75]);
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});
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});
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describe("videoProgress", () => {
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it("holds still at the start and at the end of each project's stretch", () => {
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expect(videoProgress(0)).toBe(0);
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expect(videoProgress(0.1)).toBe(0);
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expect(videoProgress(0.5)).toBeCloseTo(0.5);
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expect(videoProgress(0.9)).toBe(1);
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expect(videoProgress(1)).toBe(1);
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});
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});
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describe("videoProgress with a shorter pause at the end", () => {
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it("lets the video run until the tail starts", () => {
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expect(videoProgress(0.9, 0.1, 0.03)).toBeCloseTo((0.9 - 0.1) / 0.87, 9);
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expect(videoProgress(0.97, 0.1, 0.03)).toBe(1);
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expect(videoProgress(1, 0.1, 0.03)).toBe(1);
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expect(videoProgress(0.1, 0.1, 0.03)).toBe(0);
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});
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it("localAtProgress is its inverse inside the moving part", () => {
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for (const progress of [0, 0.25, 0.5, 1]) {
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const local = localAtProgress(progress, 0.1, 0.03);
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expect(videoProgress(local, 0.1, 0.03)).toBeCloseTo(progress, 9);
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}
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expect(localAtProgress(0)).toBe(REEL_HOLD);
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expect(localAtProgress(1)).toBeCloseTo(1 - REEL_HOLD, 9);
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});
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});
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describe("reelHolds", () => {
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it("keeps the full pause everywhere but at the end of the last project, which has nothing to wait for", () => {
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expect(reelHolds(0, 4)).toEqual({ head: REEL_HOLD, tail: REEL_HOLD });
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expect(reelHolds(2, 4)).toEqual({ head: REEL_HOLD, tail: REEL_HOLD });
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expect(reelHolds(3, 4)).toEqual({ head: REEL_HOLD, tail: REEL_LAST_TAIL });
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expect(REEL_LAST_TAIL).toBeLessThan(REEL_HOLD);
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expect(reelHolds(0, 1).tail).toBe(REEL_LAST_TAIL);
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});
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});
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describe("easeToward", () => {
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it("moves toward the target and never overshoots", () => {
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const first = easeToward(0, 1, 1 / 60);
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expect(first).toBeGreaterThan(0);
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expect(first).toBeLessThan(1);
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expect(easeToward(0.5, 0.5, 1)).toBe(0.5);
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expect(easeToward(0, 1, 10)).toBeCloseTo(1, 5);
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});
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it("does not depend on the frame rate", () => {
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let sixty = 0;
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for (let i = 0; i < 60; i += 1) sixty = easeToward(sixty, 1, 1 / 60);
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let thirty = 0;
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for (let i = 0; i < 30; i += 1) thirty = easeToward(thirty, 1, 1 / 30);
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expect(sixty).toBeCloseTo(thirty, 6);
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});
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it("stands still when no time has passed", () => {
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expect(easeToward(0.2, 1, 0)).toBe(0.2);
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});
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});
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