Add embedder event for preferred color scheme and respond to it in the LayoutThread (#34532)

* respond to winit platform theme changed event and send it to the layout thread

Signed-off-by: Lloyd Massiah <artmis9@protonmail.com>

* refactoring viewport and theme change handling functions based on feedback

Signed-off-by: Lloyd Massiah <artmis9@protonmail.com>

* fixing issues reported by test-tidy

Signed-off-by: Lloyd Massiah <artmis9@protonmail.com>

* update stylo in order to use color_scheme function on Device

Signed-off-by: Lloyd Massiah <artmis9@protonmail.com>

---------

Signed-off-by: Lloyd Massiah <artmis9@protonmail.com>
Co-authored-by: lazypassion <25536767+lazypassion@users.noreply.github.com>

components/shared/compositing/constellation_msg.rs

@@ -12,7 +12,7 @@ use embedder_traits::Cursor;
 use ipc_channel::ipc::IpcSender;
 use keyboard_types::{CompositionEvent, KeyboardEvent};
 use script_traits::{
-    AnimationTickType, CompositorEvent, GamepadEvent, LogEntry, MediaSessionActionType,
+    AnimationTickType, CompositorEvent, GamepadEvent, LogEntry, MediaSessionActionType, Theme,
     TraversalDirection, WebDriverCommandMsg, WindowSizeData, WindowSizeType,
 };
 use servo_url::ServoUrl;
@@ -46,6 +46,8 @@ pub enum ConstellationMsg {
     TraverseHistory(TopLevelBrowsingContextId, TraversalDirection),
     /// Inform the constellation of a window being resized.
     WindowSize(TopLevelBrowsingContextId, WindowSizeData, WindowSizeType),
+    /// Inform the constellation of a theme change.
+    ThemeChange(Theme),
     /// Requests that the constellation instruct layout to begin a new tick of the animation.
     TickAnimation(PipelineId, AnimationTickType),
     /// Dispatch a webdriver command
@@ -110,6 +112,7 @@ impl ConstellationMsg {
             LoadUrl(..) => "LoadUrl",
             TraverseHistory(..) => "TraverseHistory",
             WindowSize(..) => "WindowSize",
+            ThemeChange(..) => "ThemeChange",
             TickAnimation(..) => "TickAnimation",
             WebDriverCommand(..) => "WebDriverCommand",
             Reload(..) => "Reload",

components/shared/script/lib.rs

@@ -284,6 +284,8 @@ pub enum ConstellationControlMsg {
     AttachLayout(NewLayoutInfo),
     /// Window resized.  Sends a DOM event eventually, but first we combine events.
     Resize(PipelineId, WindowSizeData, WindowSizeType),
+    /// Theme changed.
+    ThemeChange(PipelineId, Theme),
     /// Notifies script that window has been resized but to not take immediate action.
     ResizeInactive(PipelineId, WindowSizeData),
     /// Window switched from fullscreen mode.
@@ -398,6 +400,7 @@ impl fmt::Debug for ConstellationControlMsg {
             NavigationResponse(..) => "NavigationResponse",
             AttachLayout(..) => "AttachLayout",
             Resize(..) => "Resize",
+            ThemeChange(..) => "ThemeChange",
             ResizeInactive(..) => "ResizeInactive",
             UnloadDocument(..) => "UnloadDocument",
             ExitPipeline(..) => "ExitPipeline",
@@ -776,6 +779,15 @@ pub enum WindowSizeType {
     Resize,
 }
 
+/// The type of platform theme.
+#[derive(Clone, Copy, Debug, Deserialize, Eq, MallocSizeOf, PartialEq, Serialize)]
+pub enum Theme {
+    /// Light theme.
+    Light,
+    /// Dark theme.
+    Dark,
+}
+
 /// Messages to the constellation originating from the WebDriver server.
 #[derive(Debug, Deserialize, Serialize)]
 pub enum WebDriverCommandMsg {

components/shared/script_layout/lib.rs

@@ -48,6 +48,7 @@ use style::invalidation::element::restyle_hints::RestyleHint;
 use style::media_queries::Device;
 use style::properties::style_structs::Font;
 use style::properties::PropertyId;
+use style::queries::values::PrefersColorScheme;
 use style::selector_parser::{PseudoElement, RestyleDamage, Snapshot};
 use style::stylesheets::Stylesheet;
 use style::Atom;
@@ -426,6 +427,8 @@ pub struct ScriptReflow {
     pub animation_timeline_value: f64,
     /// The set of animations for this document.
     pub animations: DocumentAnimationSet,
+    /// The theme for the window
+    pub theme: PrefersColorScheme,
 }
 
 /// A pending restyle.