[BUG] Chromium headless doesn't have a default prefers-color-scheme

[mxschmitt]

Context:

• Playwright Version: current tip of tree: c0c9b7f
• Operating System: macOS and also reproducible on Linux

Code Snippet

Example on Try Playwright: https://try.playwright.tech/?s=6haon

const playwright = require("playwright");

(async () => {
  for (const browserType of ['chromium', 'webkit', 'firefox']) {
    const browser = await playwright[browserType].launch();
    const context = await browser.newContext();
    const page = await context.newPage();
    console.log(await page.evaluate(() => matchMedia('(prefers-color-scheme: light)').matches));

    await browser.close();
  }
})();

Describe the bug

WebKit and Firefox have a default prefers-color-scheme but headless Chromium not.

The issue is also persistent in Puppeteer.

Expected

true
true
true

Actual

false
true
true

[mxschmitt]

Update: I found out the solution for that. On my webpage I had no default value set if the prefers-color-scheme is not there. That is now fixed: https://github.com/mxschmitt/try-playwright/pull/85/files

But maybe this issue is still relevant, because the other browsers are setting a default prefers-color-scheme but headless chromium not.

A different behaviour in the different browser engines would be not that good in my mind.

[pavelfeldman]

Additional details: when my Mac is configured for Appearance Dark, I get

false
false
true

[mxschmitt]

Great work @pavelfeldman! 👍