From 7410736b0fe0432d3179f673bf8b495b40980e3e Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 27 Sep 2021 16:34:06 +0200
Subject: [PATCH] LibWeb: Support window.devicePixelRatio

This always returns 1 for now. I've added a FIXME about returning 2 in
HiDPI mode.
---
 Userland/Libraries/LibWeb/Bindings/WindowObject.cpp | 9 +++++++++
 Userland/Libraries/LibWeb/Bindings/WindowObject.h   | 2 ++
 Userland/Libraries/LibWeb/DOM/Window.cpp            | 6 ++++++
 Userland/Libraries/LibWeb/DOM/Window.h              | 2 ++
 4 files changed, 19 insertions(+)

diff --git a/Userland/Libraries/LibWeb/Bindings/WindowObject.cpp b/Userland/Libraries/LibWeb/Bindings/WindowObject.cpp
index 4ee9eea972..74ca7db523 100644
--- a/Userland/Libraries/LibWeb/Bindings/WindowObject.cpp
+++ b/Userland/Libraries/LibWeb/Bindings/WindowObject.cpp
@@ -67,6 +67,7 @@ void WindowObject::initialize_global_object()
     define_native_accessor("screen", screen_getter, {}, JS::Attribute::Enumerable);
     define_native_accessor("innerWidth", inner_width_getter, {}, JS::Attribute::Enumerable);
     define_native_accessor("innerHeight", inner_height_getter, {}, JS::Attribute::Enumerable);
+    define_native_accessor("devicePixelRatio", device_pixel_ratio_getter, {}, JS::Attribute::Enumerable | JS::Attribute::Configurable);
     u8 attr = JS::Attribute::Writable | JS::Attribute::Enumerable | JS::Attribute::Configurable;
     define_native_function("alert", alert, 0, attr);
     define_native_function("confirm", confirm, 0, attr);
@@ -506,6 +507,14 @@ JS_DEFINE_NATIVE_FUNCTION(WindowObject::inner_height_getter)
     return JS::Value(impl->inner_height());
 }
 
+JS_DEFINE_NATIVE_FUNCTION(WindowObject::device_pixel_ratio_getter)
+{
+    auto* impl = impl_from(vm, global_object);
+    if (!impl)
+        return {};
+    return JS::Value(impl->device_pixel_ratio());
+}
+
 JS_DEFINE_NATIVE_FUNCTION(WindowObject::get_computed_style)
 {
     auto* impl = impl_from(vm, global_object);
diff --git a/Userland/Libraries/LibWeb/Bindings/WindowObject.h b/Userland/Libraries/LibWeb/Bindings/WindowObject.h
index eda6c5d72a..ffb21a6d50 100644
--- a/Userland/Libraries/LibWeb/Bindings/WindowObject.h
+++ b/Userland/Libraries/LibWeb/Bindings/WindowObject.h
@@ -81,6 +81,8 @@ private:
 
     JS_DECLARE_NATIVE_FUNCTION(parent_getter);
 
+    JS_DECLARE_NATIVE_FUNCTION(device_pixel_ratio_getter);
+
     JS_DECLARE_NATIVE_GETTER(scroll_x_getter);
     JS_DECLARE_NATIVE_GETTER(scroll_y_getter);
     JS_DECLARE_NATIVE_FUNCTION(scroll);
diff --git a/Userland/Libraries/LibWeb/DOM/Window.cpp b/Userland/Libraries/LibWeb/DOM/Window.cpp
index 217eb213e5..a93eb58885 100644
--- a/Userland/Libraries/LibWeb/DOM/Window.cpp
+++ b/Userland/Libraries/LibWeb/DOM/Window.cpp
@@ -309,4 +309,10 @@ void Window::queue_microtask(JS::FunctionObject& callback)
     });
 }
 
+float Window::device_pixel_ratio() const
+{
+    // FIXME: Return 2.0f if we're in HiDPI mode!
+    return 1.0f;
+}
+
 }
diff --git a/Userland/Libraries/LibWeb/DOM/Window.h b/Userland/Libraries/LibWeb/DOM/Window.h
index 9cd6f952a0..7c4152ac64 100644
--- a/Userland/Libraries/LibWeb/DOM/Window.h
+++ b/Userland/Libraries/LibWeb/DOM/Window.h
@@ -87,6 +87,8 @@ public:
 
     void fire_a_page_transition_event(FlyString event_name, bool persisted);
 
+    float device_pixel_ratio() const;
+
 private:
     explicit Window(Document&);