When can Playwright's Page.ViewportSize be null?

Question

The Page.ViewportSize property is defined as nullable.

Under what conditions could it be null?

Answer 1

Viewport: null is mainly for headful / interactive mode . It simply means that the user would set the viewport size via resizing the window.

NOTE: The null value opts out from the default presets, makes viewport depend on the host window size defined by the operating system. It makes the execution of the tests non-deterministic.

Code Example:

const playwright = require('playwright');

    (async () => {
      for (const browserType of ['chromium', 'firefox', 'webkit']) {
        const browser = await playwright[browserType].launch();
        const context = await browser.newContext({
          viewport: null
        });
        const page = await context.newPage();
        await page.goto('https://google.com');
        
       
        await page.screenshot({ path: `example-${browserType}.png` });
        await browser.close();
      }
    })();

Reference: https://github.com/microsoft/playwright/issues/2170