electron-win10darktheme-workaround.ts

// Work-around for this Electron bug: https://github.com/electron/electron/issues/19468

import { execSync } from 'child_process'
import { app } from 'electron'

function setWindowsAppTheme(light: boolean) {
  try {
    execSync(
      `REG ADD HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize /v AppsUseLightTheme /t REG_DWORD /d ${ light ? 1 : 0 } /f`,
      { windowsHide: true }
    )
  } catch(error) {
    throw new Error('No permission to modify AppsUseLightTheme value. Electron will hang.')
  }
}

// Validates that reg value exists and is set to 1
function isCurrentAppThemeLight(): boolean {
  let result: string | RegExpMatchArray | null | number
  try {
    // Check if value exists in registry
    result = execSync(
      'REG QUERY HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize /v AppsUseLightTheme /t REG_DWORD',
      { encoding: 'utf8', windowsHide: true}
    )
  } catch(error) {
    // Value doesn't exist.
    throw new Error('Could not find registry value')
  }
  result = result.match(/0x\d+$/im)
  if (result === null)
    throw new Error('Unexpected output from reg.exe')
  result = parseInt(result[0], 16)
  if (isNaN(result))
    throw new Error('Unexpected output from reg.exe')
  return result === 1
}

let hasBeenCalled = false

export default function initDarkThemeWorkAround(): boolean {
  if (hasBeenCalled) return false
  hasBeenCalled = true

  // This workaround does not apply to anything but Windows.
  if (process.platform !== 'win32') return false
  try {
    if (isCurrentAppThemeLight()) return false
  } catch(error) {
    // Unsupported Windows version.
    return false
  }

  app.on('will-finish-launching', () => {
    setWindowsAppTheme(true)
  })
  
  app.on('ready', () => {
    setWindowsAppTheme(false)
  })

  return true
}

The isCurrentAppThemeLight function can be removed and Electron's nativeTheme.shouldUseDarkColors used instead.

@cmeeren isCurrentAppThemeLight is also used to check if the reg value exists so we wouldn't accidentally create a reg value instead of modifying it.

• Is it possible for the reg key to not exist if nativeTheme.shouldUseDarkColors returns true?
• If it is, then AFAIK this fix won't work anyway because then it won't set the theme to Light, so it's a moot point?
• In any case, is it that bad to add the reg key if it doesn't exist, given that the theme is reverted anyway? IMHO the simplicity of nativeTheme.shouldUseDarkColors vs. the isCurrentAppThemeLight implementation makes it worth it, but please let me know if this is wrong in some critical way.

@cmeeren Don't know, no answer, and I rather not have this script be the source of somebody's build of Windows blue screening because Microsoft didn't do QA for random registry values existing in Windows builds where they shouldn't.

Thank you so much for this