fix: take device_pixel_ratio into account

.rspec

@@ -1,4 +1,3 @@
 --color
---fail-fast
 --format=doc
 --require spec_helper

CHANGELOG.md

@@ -1,6 +1,8 @@
 ## [Unreleased](https://github.com/rubycdp/ferrum/compare/v0.13...main) ##
 
 ### Added
+- `Ferrum::Page#device_pixel_ratio` returns the ratio of the resolution in physical pixels to the
+  resolution in CSS pixels for the current display device.
 - `Ferrum::Network#cache(disable: true | false)` whether or not to use cache for every request
 - `Ferrum::Network::Exchange#redirect?` determines if the exchange is a redirect
 - `Ferrum::Network::Exchange#xhr?` determines if the exchange is XHR

lib/ferrum/browser.rb

@@ -22,7 +22,7 @@ class Browser
                 body doctype content=
                 headers cookies network
                 mouse keyboard
-                screenshot pdf mhtml viewport_size
+                screenshot pdf mhtml viewport_size device_pixel_ratio
                 frames frame_by main_frame
                 evaluate evaluate_on evaluate_async execute evaluate_func
                 add_script_tag add_style_tag bypass_csp

lib/ferrum/page.rb

@@ -145,7 +145,7 @@ def resize(width: nil, height: nil, fullscreen: false)
       command("Emulation.setDeviceMetricsOverride", slowmoable: true,
                                                     width: width,
                                                     height: height,
-                                                    deviceScaleFactor: 1,
+                                                    deviceScaleFactor: 0,
                                                     mobile: false,
                                                     fitWindow: false)
     end

lib/ferrum/page/screenshot.rb

@@ -147,6 +147,12 @@ def viewport_size
         JS
       end
 
+      def device_pixel_ratio
+        evaluate <<~JS
+          window.devicePixelRatio
+        JS
+      end
+
       def document_size
         evaluate <<~JS
           [document.documentElement.scrollWidth,

spec/page/screenshot_spec.rb

@@ -13,15 +13,14 @@
       create_screenshot(path: file)
 
       File.open(file, "rb") do |f|
-        expect(ImageSize.new(f.read).size).to eq(browser.viewport_size)
+        expect(ImageSize.new(f.read).size).to eq(browser.viewport_size.map { |s| s * device_pixel_ratio })
       end
 
       create_screenshot(path: file, full: true)
 
       File.open(file, "rb") do |f|
-        expect(ImageSize.new(f.read).size).to eq(
-          browser.evaluate("[document.documentElement.clientWidth, document.documentElement.clientHeight]")
-        )
+        size = browser.evaluate("[document.documentElement.clientWidth, document.documentElement.clientHeight]")
+        expect(ImageSize.new(f.read).size).to eq(size.map { |s| s * device_pixel_ratio })
       end
     end
 
@@ -31,7 +30,7 @@
       create_screenshot(path: file, full: true)
 
       File.open(file, "rb") do |f|
-        expect(ImageSize.new(f.read).size).to eq(browser.viewport_size)
+        expect(ImageSize.new(f.read).size).to eq(browser.viewport_size.map { |s| s * device_pixel_ratio })
       end
     end
 
@@ -48,7 +47,7 @@
             return [rect.width, rect.height];
           }();
         JS
-        expect(ImageSize.new(f.read).size).to eq(size)
+        expect(ImageSize.new(f.read).size).to eq(size.map { |s| s * device_pixel_ratio })
       end
     end
 
@@ -59,9 +58,8 @@
       create_screenshot(path: file, full: true, selector: "#penultimate")
 
       File.open(file, "rb") do |f|
-        expect(ImageSize.new(f.read).size).to eq(
-          browser.evaluate("[document.documentElement.clientWidth, document.documentElement.clientHeight]")
-        )
+        size = browser.evaluate("[document.documentElement.clientWidth, document.documentElement.clientHeight]")
+        expect(ImageSize.new(f.read).size).to eq(size.map { |s| s * device_pixel_ratio })
       end
     end
 
@@ -99,6 +97,7 @@
   describe "#screenshot" do
     let(:format) { :png }
     let(:file) { "#{PROJECT_ROOT}/spec/tmp/screenshot.#{format}" }
+    let(:device_pixel_ratio) { browser.device_pixel_ratio }
 
     def create_screenshot(**options)
       browser.screenshot(**options)
@@ -165,7 +164,7 @@ def create_screenshot(**options)
         browser.screenshot(path: file, full: true)
 
         File.open(file, "rb") do |f|
-          expect(ImageSize.new(f.read).size).to eq([1280, 1024])
+          expect(ImageSize.new(f.read).size).to eq([1280, 1024].map { |s| s * device_pixel_ratio })
         end
         expect(browser.viewport_size).to eq([1024, 768])
       end