RUWIO/scripts/verify-capture-fidelity.cjs

// Compares Electron capturePage output against render.html's own canvas pixels
// for deterministic fixture scenes. This guards the capture step itself:
// wrong scale-factor normalization, stale frames, and clipping show up here.

const { app, BrowserWindow, nativeImage } = require('electron')
const fs = require('node:fs')
const path = require('node:path')
const { pathToFileURL } = require('node:url')
const { diffBgra } = require('../test/lib/pixelDiff.cjs')

const fixtures = [
  {
    file: path.join(process.cwd(), 'test', 'fixtures', 'scenes', 'capture-basic.json'),
    times: [0, 0.5, 1],
  },
]

function createRenderWindow(scene) {
  return new BrowserWindow({
    width: scene.canvas.width,
    height: scene.canvas.height,
    show: false,
    frame: false,
    transparent: false,
    backgroundColor: '#ffffff',
    webPreferences: {
      contextIsolation: true,
      nodeIntegration: false,
      sandbox: true,
      backgroundThrottling: false,
      partition: 'ruwio-capture-fidelity',
    },
  })
}

async function main() {
  let pass = true
  const notes = []
  const renderHtml = path.join(process.cwd(), 'server', 'render.html')

  for (const fixture of fixtures) {
    const scene = JSON.parse(fs.readFileSync(fixture.file, 'utf8'))
    const win = createRenderWindow(scene)
    win.webContents.session.webRequest.onBeforeRequest(
      { urls: ['*://*/*'] },
      (_details, callback) => callback({ cancel: true }),
    )
    win.webContents.setWindowOpenHandler(() => ({ action: 'deny' }))
    win.webContents.on('will-navigate', (event) => event.preventDefault())

    try {
      await win.loadURL(pathToFileURL(renderHtml).toString())
      await win.webContents.executeJavaScript(`window.__animatrInit(${JSON.stringify(scene)})`, true)

      for (const t of fixture.times) {
        await win.webContents.executeJavaScript(`window.__animatrSeek(${t})`, true)
        const capture = await win.webContents.capturePage({
          x: 0,
          y: 0,
          width: scene.canvas.width,
          height: scene.canvas.height,
        })
        const canvasDataUrl = await win.webContents.executeJavaScript(
          `document.querySelector('canvas').toDataURL('image/png')`,
          true,
        )
        const expected = nativeImage.createFromDataURL(canvasDataUrl)
        const captureSize = capture.getSize()
        const expectedSize = expected.getSize()
        if (captureSize.width !== scene.canvas.width || captureSize.height !== scene.canvas.height) {
          pass = false
          notes.push(`${path.basename(fixture.file)} t=${t}: capture size ${captureSize.width}x${captureSize.height}`)
          continue
        }
        if (expectedSize.width !== scene.canvas.width || expectedSize.height !== scene.canvas.height) {
          pass = false
          notes.push(`${path.basename(fixture.file)} t=${t}: canvas size ${expectedSize.width}x${expectedSize.height}`)
          continue
        }
        const diff = diffBgra(capture.getBitmap(), expected.getBitmap(), {
          // capturePage composites the hidden window, which introduces
          // sub-perceptual AA/rounding noise (~maxDelta 6/255 on shape edges)
          // versus the raw canvas toDataURL. Tolerate that; genuine render
          // drift (wrong color, missing or stale shape, off-by-one frame)
          // produces much larger deltas over a contiguous region and still
          // trips the ratio gate. The explicit size checks above catch #10/#11.
          perChannelTolerance: 8,
          maxMismatchedRatio: 0.02,
        })
        console.log(
          `${path.basename(fixture.file)} t=${t}: mismatch=${diff.mismatchedPixels}/${diff.pixels} ` +
            `(${(diff.mismatchedRatio * 100).toFixed(4)}%) maxDelta=${diff.maxDelta} meanDelta=${diff.meanDelta.toFixed(3)}`,
        )
        if (!diff.ok) {
          pass = false
          notes.push(
            `${path.basename(fixture.file)} t=${t}: diff exceeds tolerance ` +
              `${diff.mismatchedPixels}/${diff.pixels}, maxDelta=${diff.maxDelta}`,
          )
        }
      }
    } finally {
      if (!win.isDestroyed()) win.close()
    }
  }

  console.log(notes.length ? 'NOTES:\n  ' + notes.join('\n  ') : 'NOTES: none')
  console.log(pass ? 'RESULT: PASS' : 'RESULT: FAIL')
  app.exit(pass ? 0 : 1)
}

app.on('window-all-closed', () => {})
app.commandLine.appendSwitch('disable-gpu')

app.whenReady().then(() =>
  main().catch((err) => {
    console.error('HARNESS ERROR:', err)
    app.exit(2)
  }),
)