orca/mobile/plugins/android-window-density.js

const { AndroidConfig, withAndroidManifest, withMainActivity } = require('expo/config-plugins')

// Why: One UI gives a split-screen pane its own density (#36305). Without `density` in
// configChanges Android recreates MainActivity, closing the open session and orphaning the image
// picker. Keeping the activity is not enough: React Native seeds its DisplayMetricsHolder from the
// application context, which keeps the full-screen density, so the pane is laid out at the wrong
// scale. MainActivity re-seeds it from its own resources after React Native does.
const MARKER = 'orca: window density'

const CLASS_HEADER = 'class MainActivity : ReactActivity() {'
const IMPORTS = [
  'android.content.res.Configuration',
  'android.os.Bundle',
  'android.util.DisplayMetrics',
  'com.facebook.react.uimanager.DisplayMetricsHolder'
]

const METHODS = `
  // ${MARKER}, generated by plugins/android-window-density.js.
  // React Native re-seeds from the application context when it creates the root view (onCreate)
  // and in onConfigurationChanged, so these run before the next measure. Its root view's layout
  // listener also re-seeds whenever the rotation differs from the last one it saw, after measuring;
  // the pre-draw check runs after every layout listener and asks for another pass, in which React
  // Native re-sends the window size to JS.
  override fun onPostCreate(savedInstanceState: Bundle?) {
    super.onPostCreate(savedInstanceState)
    window.decorView.viewTreeObserver.addOnPreDrawListener {
      val held = DisplayMetricsHolder.getScreenDisplayMetrics().densityDpi
      if (held != resources.displayMetrics.densityDpi) {
        useWindowDensity()
        window.decorView.requestLayout()
      }
      true
    }
  }

  override fun onResume() {
    super.onResume()
    useWindowDensity()
  }

  override fun onConfigurationChanged(newConfig: Configuration) {
    super.onConfigurationChanged(newConfig)
    useWindowDensity()
  }

  // React Native's initDisplayMetrics with the pane's density on the real display size, built before
  // it is published because text measurement reads it off the UI thread.
  @Suppress("DEPRECATION")
  private fun useWindowDensity() {
    val pane = resources.displayMetrics
    val screen = DisplayMetrics().apply {
      windowManager.defaultDisplay.getRealMetrics(this)
      density = pane.density
      densityDpi = pane.densityDpi
      scaledDensity = pane.scaledDensity
    }
    DisplayMetricsHolder.setScreenDisplayMetrics(screen)
  }
`

function patchMainActivity(contents) {
  if (contents.includes(MARKER)) {
    return contents
  }
  // A changed template must fail prebuild rather than drop or double an override.
  if (
    !contents.includes(CLASS_HEADER) ||
    !contents.trimEnd().endsWith('}') ||
    /fun (onPostCreate|onResume|onConfigurationChanged)\(/.test(contents)
  ) {
    throw new Error(
      "android-window-density: Expo's MainActivity template changed; update the plugin before building."
    )
  }
  const imports = IMPORTS.filter((name) => !contents.includes(`import ${name}\n`))
    .map((name) => `import ${name}\n`)
    .join('')
  const body = contents.trimEnd().slice(0, -1).trimEnd()
  return `${body.replace(/^(package [^\n]+\n)/, `$1${imports}`)}\n${METHODS}}\n`
}

module.exports = function withAndroidWindowDensity(config) {
  config = withAndroidManifest(config, (cfg) => {
    const activity = AndroidConfig.Manifest.getMainActivityOrThrow(cfg.modResults)
    const changes = (activity.$['android:configChanges'] ?? '').split('|').filter(Boolean)
    if (!changes.includes('density')) {
      activity.$['android:configChanges'] = [...changes, 'density'].join('|')
    }
    return cfg
  })

  return withMainActivity(config, (cfg) => {
    if (cfg.modResults.language !== 'kt') {
      throw new Error(
        `android-window-density: expected a Kotlin MainActivity, got ${cfg.modResults.language}`
      )
    }
    cfg.modResults.contents = patchMainActivity(cfg.modResults.contents)
    return cfg
  })
}