feuerwerk/tests/viewport/view.test.ts

/** The viewport transforms: plain geometry, so pinned here rather than through the browser. */
import { describe, expect, it } from 'vitest';
import {
  cameraFactor,
  cameraView,
  FREE_ZOOM_STEPS,
  freeView,
  GAME_SCALE_STEPS,
  gameScaleFactor,
  isInside,
  nearestZoomStep,
  screenToWorld,
  stepFreeZoom,
  worldBounds,
  worldToScreen,
  zoomStepBelow,
} from '../../src/viewport/view';

describe('freeView', () => {
  it('puts the view centre in the middle of the widget', () => {
    const view = freeView(50, -20, 2, 800, 600);
    expect(worldToScreen(view, 50, -20)).toEqual({ x: 400, y: 300 });
    expect(screenToWorld(view, 400, 300)).toEqual({ x: 50, y: -20 });
  });

  it('scales distances by the zoom', () => {
    const view = freeView(0, 0, 2, 800, 600);
    expect(worldToScreen(view, 100, 0)).toEqual({ x: 600, y: 300 });
  });

  it('round-trips any point', () => {
    const view = freeView(13, -7, 0.35, 640, 480);
    const back = screenToWorld(view, ...(Object.values(worldToScreen(view, 123, -456)) as [number, number]));
    expect(back.x).toBeCloseTo(123, 9);
    expect(back.y).toBeCloseTo(-456, 9);
  });

  it('covers the widget in world units', () => {
    const bounds = worldBounds(freeView(0, 0, 2, 800, 600));
    expect(bounds).toEqual({ left: -200, top: -150, right: 200, bottom: 150 });
  });
});

describe('free view zoom steps under Windows scaling', () => {
  it('zoom counts device pixels, so zoom 1 at 125% is one screen pixel per world pixel', () => {
    const view = freeView(0, 0, 1, 800, 600, 1.25);
    expect(view.scale * 1.25).toBe(1);
    expect(freeView(0, 0, 3, 800, 600, 1.25).scale * 1.25).toBeCloseTo(3, 12);
  });

  it('every step gives each texel a whole number of device pixels, or a whole fraction below 1', () => {
    for (const step of FREE_ZOOM_STEPS)
      expect(step >= 1 ? Number.isInteger(step) : Number.isInteger(1 / step)).toBe(true);
  });

  it('the wheel moves one step and stays at the ends', () => {
    expect(stepFreeZoom(1, 1)).toBe(2);
    expect(stepFreeZoom(2, -1)).toBe(1);
    expect(stepFreeZoom(1, -1)).toBe(0.5);
    expect(stepFreeZoom(6, 1)).toBe(8);
    expect(stepFreeZoom(24, 1)).toBe(24);
    expect(stepFreeZoom(0.125, -1)).toBe(0.125);
  });

  it('fit rounds down to a step, and a saved zoom snaps to the nearest', () => {
    expect(zoomStepBelow(2.9)).toBe(2);
    expect(zoomStepBelow(0.7)).toBe(0.5);
    expect(zoomStepBelow(0.01)).toBe(0.125);
    expect(zoomStepBelow(20)).toBe(16);
    expect(zoomStepBelow(100)).toBe(24);
    expect(nearestZoomStep(1.37)).toBe(1);
    expect(nearestZoomStep(0.4)).toBe(0.5);
  });
});

describe('cameraView', () => {
  const camera = { x: 10, y: 20, props: { width: 640, height: 360 } };

  it('fits the camera frame into the widget and centres it', () => {
    // 640×360 into 800×600: width is the tighter fit (1.25 vs 1.67), so bars top and bottom.
    const view = cameraView(camera, 800, 600);
    expect(view.scale).toBeCloseTo(1.25, 9);
    expect(view.rect).toEqual({ x: 0, y: 75, w: 800, h: 450 });
    // The camera position sits at the centre of the frame, not of the widget.
    expect(worldToScreen(view, 10, 20)).toEqual({ x: 400, y: 300 });
  });

  it('reports the letterbox as outside', () => {
    const view = cameraView(camera, 800, 600);
    expect(isInside(view, 400, 300)).toBe(true);
    expect(isInside(view, 400, 20)).toBe(false); // top bar
    expect(isInside(view, 400, 580)).toBe(false); // bottom bar
  });

  it('draws a fixed step at exactly that many pixels per unit, starting on a whole pixel', () => {
    const view = cameraView(camera, 801, 601, 0.5);
    expect(view.scale).toBe(0.5);
    expect(view.rect).toEqual({ x: 241, y: 211, w: 320, h: 180 });
  });

  it('cuts a frame larger than the view to the view, keeping the camera in the middle', () => {
    const view = cameraView(camera, 800, 600, 2);
    expect(view.scale).toBe(2);
    expect(view.rect).toEqual({ x: 0, y: 0, w: 800, h: 600 });
    expect(worldToScreen(view, 10, 20)).toEqual({ x: 400, y: 300 });
    expect(worldBounds(view)).toEqual({ left: -190, top: -130, right: 210, bottom: 170 });
    expect(isInside(view, 1, 1)).toBe(true);
  });
});

describe('cameraView with a zoomed camera', () => {
  const zoomed = { x: 0, y: 0, props: { width: 640, height: 360, zoom: 2 } };

  it('100% shows the camera picture pixel for pixel, the zoom magnifies the world on top', () => {
    const view = cameraView(zoomed, 800, 600, 1);
    expect(view.scale).toBe(2);
    expect(view.rect).toEqual({ x: 80, y: 120, w: 640, h: 360 });
  });

  it('fit and auto size the picture, not the world region', () => {
    expect(cameraFactor(zoomed.props, 800, 600, 'fit')).toBeCloseTo(1.25, 9);
    expect(cameraView(zoomed, 800, 600, 'fit').scale).toBeCloseTo(2.5, 9);
    expect(cameraFactor(zoomed.props, 800, 600, 'auto')).toBe(1);
  });
});

describe('cameraView under Windows scaling at 125%', () => {
  const plain = { x: 0, y: 0, props: { width: 640, height: 360, zoom: 1 } };

  it('100% is one device pixel per camera pixel, starting on a whole device pixel', () => {
    const view = cameraView(plain, 801, 601, 1, 1.25);
    expect(view.scale * 1.25).toBeCloseTo(1, 12);
    expect(view.rect.w).toBeCloseTo(512, 12);
    expect(view.rect.h).toBeCloseTo(288, 12);
    expect(view.rect.x * 1.25).toBeCloseTo(181, 9);
    expect(view.rect.y * 1.25).toBeCloseTo(196, 9);
  });

  it('auto picks the step in device pixels, and fit reports device pixels', () => {
    expect(cameraFactor(plain.props, 1100, 700, 'auto', 1.25)).toBe(2);
    expect(cameraFactor(plain.props, 1100, 700, 'auto')).toBe(1);
    expect(cameraFactor(plain.props, 800, 600, 'fit', 1.25)).toBeCloseTo(1.5625, 9);
    expect(cameraView(plain, 800, 600, 'fit', 1.25).scale).toBeCloseTo(1.25, 9);
  });
});

describe('gameScaleFactor', () => {
  it('fit is the exact factor that fills the tighter side', () => {
    expect(gameScaleFactor('fit', 640, 360, 800, 600)).toBeCloseTo(1.25, 9);
  });

  it('auto takes the largest step that still fits', () => {
    expect(gameScaleFactor('auto', 640, 360, 800, 600)).toBe(1);
    expect(gameScaleFactor('auto', 640, 360, 1280, 720)).toBe(2);
    expect(gameScaleFactor('auto', 640, 360, 639, 600)).toBe(0.5);
    expect(gameScaleFactor('auto', 320, 180, 2000, 2000)).toBe(4);
  });

  it('auto falls back to the smallest step when not even that fits', () => {
    expect(gameScaleFactor('auto', 4000, 4000, 800, 600)).toBe(0.25);
  });

  it('a fixed step ignores the view size', () => {
    for (const step of GAME_SCALE_STEPS) expect(gameScaleFactor(step, 640, 360, 10, 10)).toBe(step);
  });
});