constellation: Pass system theme to new Pipelines (#37132)

Previously, when the theme was set it was only set on currently active
`Window`s. This change makes setting the `Theme` stateful. Now the
`Constellation` tracks what theme is applied to a `WebView` and properly
passes that value to new `Pipeline`s when they are constructed. In
addition, the value is passed to layout when that is constructed as
well.

Testing: this change adds a unit test.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/shared/constellation/from_script_message.rs

@@ -16,7 +16,7 @@ use canvas_traits::canvas::{CanvasId, CanvasMsg};
 use devtools_traits::{DevtoolScriptControlMsg, ScriptToDevtoolsControlMsg, WorkerId};
 use embedder_traits::{
     AnimationState, EmbedderMsg, FocusSequenceNumber, JSValue, JavaScriptEvaluationError,
-    JavaScriptEvaluationId, MediaSessionEvent, TouchEventResult, ViewportDetails,
+    JavaScriptEvaluationId, MediaSessionEvent, Theme, TouchEventResult, ViewportDetails,
     WebDriverMessageId,
 };
 use euclid::default::Size2D as UntypedSize2D;
@@ -417,6 +417,8 @@ pub struct IFrameLoadInfoWithData {
     pub sandbox: IFrameSandboxState,
     /// The initial viewport size for this iframe.
     pub viewport_details: ViewportDetails,
+    /// The [`Theme`] to use within this iframe.
+    pub theme: Theme,
 }
 
 /// Resources required by workerglobalscopes

components/shared/constellation/lib.rs

@@ -55,7 +55,7 @@ pub enum EmbedderToConstellationMessage {
     /// Inform the Constellation that a `WebView`'s [`ViewportDetails`] have changed.
     ChangeViewportDetails(WebViewId, ViewportDetails, WindowSizeType),
     /// Inform the constellation of a theme change.
-    ThemeChange(Theme),
+    ThemeChange(WebViewId, Theme),
     /// Requests that the constellation instruct script/layout to try to layout again and tick
     /// animations.
     TickAnimation(Vec<WebViewId>),

components/shared/embedder/Cargo.toml

@@ -35,6 +35,7 @@ serde = { workspace = true }
 servo_url = { path = "../../url" }
 strum_macros = { workspace = true }
 stylo_traits = { workspace = true }
+stylo = { workspace = true }
 url = { workspace = true }
 webdriver = { workspace = true }
 webrender_api = { workspace = true }

components/shared/embedder/lib.rs

@@ -34,6 +34,7 @@ use pixels::Image;
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 use servo_url::ServoUrl;
 use strum_macros::IntoStaticStr;
+use style::queries::values::PrefersColorScheme;
 use style_traits::CSSPixel;
 use url::Url;
 use webrender_api::units::{DeviceIntPoint, DeviceIntRect, DeviceIntSize, DevicePixel};
@@ -598,6 +599,16 @@ pub enum Theme {
     /// Dark theme.
     Dark,
 }
+
+impl From<Theme> for PrefersColorScheme {
+    fn from(value: Theme) -> Self {
+        match value {
+            Theme::Light => PrefersColorScheme::Light,
+            Theme::Dark => PrefersColorScheme::Dark,
+        }
+    }
+}
+
 // The type of MediaSession action.
 /// <https://w3c.github.io/mediasession/#enumdef-mediasessionaction>
 #[derive(Clone, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize)]

components/shared/script/lib.rs

@@ -68,6 +68,8 @@ pub struct NewLayoutInfo {
     pub load_data: LoadData,
     /// Initial [`ViewportDetails`] for this layout.
     pub viewport_details: ViewportDetails,
+    /// The [`Theme`] of the new layout.
+    pub theme: Theme,
 }
 
 /// When a pipeline is closed, should its browsing context be discarded too?
@@ -321,6 +323,8 @@ pub struct InitialScriptState {
     pub devtools_server_sender: Option<IpcSender<ScriptToDevtoolsControlMsg>>,
     /// Initial [`ViewportDetails`] for the frame that is initiating this `ScriptThread`.
     pub viewport_details: ViewportDetails,
+    /// Initial [`Theme`] for the frame that is initiating this `ScriptThread`.
+    pub theme: Theme,
     /// The ID of the pipeline namespace for this script thread.
     pub pipeline_namespace_id: PipelineNamespaceId,
     /// A ping will be sent on this channel once the script thread shuts down.

components/shared/script_layout/lib.rs

@@ -20,7 +20,7 @@ use base::Epoch;
 use base::id::{BrowsingContextId, PipelineId, WebViewId};
 use compositing_traits::CrossProcessCompositorApi;
 use constellation_traits::{LoadData, ScrollState};
-use embedder_traits::{UntrustedNodeAddress, ViewportDetails};
+use embedder_traits::{Theme, UntrustedNodeAddress, ViewportDetails};
 use euclid::default::{Point2D, Rect};
 use fnv::FnvHashMap;
 use fonts::{FontContext, SystemFontServiceProxy};
@@ -46,7 +46,6 @@ use style::invalidation::element::restyle_hints::RestyleHint;
 use style::media_queries::Device;
 use style::properties::PropertyId;
 use style::properties::style_structs::Font;
-use style::queries::values::PrefersColorScheme;
 use style::selector_parser::{PseudoElement, RestyleDamage, Snapshot};
 use style::stylesheets::Stylesheet;
 use webrender_api::ImageKey;
@@ -182,6 +181,7 @@ pub struct LayoutConfig {
     pub time_profiler_chan: time::ProfilerChan,
     pub compositor_api: CrossProcessCompositorApi,
     pub viewport_details: ViewportDetails,
+    pub theme: Theme,
 }
 
 pub trait LayoutFactory: Send + Sync {
@@ -428,7 +428,7 @@ pub struct ReflowRequest {
     /// The set of image animations.
     pub node_to_image_animation_map: FxHashMap<OpaqueNode, ImageAnimationState>,
     /// The theme for the window
-    pub theme: PrefersColorScheme,
+    pub theme: Theme,
     /// The node highlighted by the devtools, if any
     pub highlighted_dom_node: Option<OpaqueNode>,
 }