feat(BREAKING): Set DPR to 1 for Chrome headless browsers by default (#17377)

packages/server/lib/browsers/chrome.ts

@@ -429,6 +429,10 @@ export = {
       // set default headless size to 1920x1080
       // https://github.com/cypress-io/cypress/issues/6210
       args.push('--window-size=1920,1080')
+
+      // set default headless DPR to 1
+      // https://github.com/cypress-io/cypress/issues/17375
+      args.push('--force-device-scale-factor=1')
     }
 
     // force ipv4

packages/server/test/e2e/5_headless_spec.ts

@@ -84,4 +84,10 @@ describe('e2e headless', function () {
     project: Fixtures.projectPath('screen-size'),
     spec: 'default_size.spec.js',
   })
+
+  e2e.it('launches at DPR 1x', {
+    headed: false,
+    project: Fixtures.projectPath('screen-size'),
+    spec: 'device_pixel_ratio.spec.js',
+  })
 })

packages/server/test/support/fixtures/projects/screen-size/cypress/integration/device_pixel_ratio.spec.js

@@ -0,0 +1,6 @@
+describe('devicePixelRatio', () => {
+  it('has DPR of 1', () => {
+    // assert the browser was spawned with DPR of 1
+    expect(window.devicePixelRatio).to.equal(1)
+  })
+})

packages/server/test/support/fixtures/projects/screen-size/cypress/plugins/index.js

@@ -4,6 +4,7 @@
 module.exports = (on) => {
   on('before:browser:launch', (browser, options) => {
     // options.args.push('-width', '1280', '-height', '1024')
+    // options.args.push('--force-device-scale-factor=2')
 
     // return options
   })

packages/server/test/unit/browsers/chrome_spec.js

@@ -99,7 +99,7 @@ describe('lib/browsers/chrome', () => {
       })
     })
 
-    it('sets default window size in headless mode', function () {
+    it('sets default window size and DPR in headless mode', function () {
       chrome._writeExtension.restore()
 
       return chrome.open({ isHeadless: true, isHeaded: false }, 'http://', {}, this.automation)
@@ -109,6 +109,7 @@ describe('lib/browsers/chrome', () => {
         expect(args).to.include.members([
           '--headless',
           '--window-size=1920,1080',
+          '--force-device-scale-factor=1',
         ])
       })
     })