Process colorSchemeSimulation in TargetConfigurationActor (#36297)

Implements Steps 1,4&6 of https://github.com/servo/servo/issues/35867:
- Adds `pub simulate_color_scheme` to `BrowsingContextActor` using
`script_chan`.
- Processes `colorSchemeSimulation` flag in `TargetConfigurationActor`’s
`updateConfiguration`.
- Routes `colorSchemeSimulation` from `RootActor` via
`TabDescriptorActor` to `BrowsingContextActor`.

Testing: Compiles and lints clean.
Fixes: https://github.com/servo/servo/issues/35867

---------

Signed-off-by: Uthman Yahaya Baba <uthmanyahayababa@gmail.com>

3 files changed, 44 insertions, 7 deletions

diff --git a/components/devtools/actors/browsing_context.rs b/components/devtools/actors/browsing_context.rs
index 261eb4112bf..9a037c11428 100644
--- a/components/devtools/actors/browsing_context.rs
+++ b/components/devtools/actors/browsing_context.rs
@@ -11,8 +11,11 @@ use std::collections::HashMap;
 use std::net::TcpStream;
 
 use base::id::PipelineId;
-use devtools_traits::DevtoolScriptControlMsg::{self, GetCssDatabase, WantsLiveNotifications};
+use devtools_traits::DevtoolScriptControlMsg::{
+    self, GetCssDatabase, SimulateColorScheme, WantsLiveNotifications,
+};
 use devtools_traits::{DevtoolsPageInfo, NavigationState};
+use embedder_traits::Theme;
 use ipc_channel::ipc::{self, IpcSender};
 use serde::Serialize;
 use serde_json::{Map, Value};
@@ -352,4 +355,10 @@ impl BrowsingContextActor {
             let _ = stream.write_json_packet(&msg);
         }
     }
+
+    pub fn simulate_color_scheme(&self, theme: Theme) -> Result<(), ()> {
+        self.script_chan
+            .send(SimulateColorScheme(self.active_pipeline_id.get(), theme))
+            .map_err(|_| ())
+    }
 }
diff --git a/components/devtools/actors/watcher/target_configuration.rs b/components/devtools/actors/watcher/target_configuration.rs
index 7b83cdde698..0d366e81475 100644
--- a/components/devtools/actors/watcher/target_configuration.rs
+++ b/components/devtools/actors/watcher/target_configuration.rs
@@ -8,12 +8,16 @@
 use std::collections::HashMap;
 use std::net::TcpStream;
 
+use embedder_traits::Theme;
+use log::warn;
 use serde::Serialize;
 use serde_json::{Map, Value};
 
 use crate::actor::{Actor, ActorMessageStatus, ActorRegistry};
+use crate::actors::browsing_context::BrowsingContextActor;
+use crate::actors::tab::TabDescriptorActor;
 use crate::protocol::JsonPacketStream;
-use crate::{EmptyReplyMsg, StreamId};
+use crate::{EmptyReplyMsg, RootActor, StreamId};
 
 #[derive(Serialize)]
 #[serde(rename_all = "camelCase")]
@@ -44,15 +48,39 @@ impl Actor for TargetConfigurationActor {
     /// - `updateConfiguration`: Receives new configuration flags from the devtools host.
     fn handle_message(
         &self,
-        _registry: &ActorRegistry,
+        registry: &ActorRegistry,
         msg_type: &str,
-        _msg: &Map<String, Value>,
+        msg: &Map<String, Value>,
         stream: &mut TcpStream,
         _id: StreamId,
     ) -> Result<ActorMessageStatus, ()> {
         Ok(match msg_type {
             "updateConfiguration" => {
-                // TODO: Actually update configuration
+                let config = match msg.get("configuration").and_then(|v| v.as_object()) {
+                    Some(config) => config,
+                    None => {
+                        let msg = EmptyReplyMsg { from: self.name() };
+                        let _ = stream.write_json_packet(&msg);
+                        return Ok(ActorMessageStatus::Processed);
+                    },
+                };
+                if let Some(scheme) = config.get("colorSchemeSimulation").and_then(|v| v.as_str()) {
+                    let theme = match scheme {
+                        "dark" => Theme::Dark,
+                        "light" => Theme::Light,
+                        _ => Theme::Light,
+                    };
+                    let root_actor = registry.find::<RootActor>("root");
+                    if let Some(tab_name) = root_actor.active_tab() {
+                        let tab_actor = registry.find::<TabDescriptorActor>(&tab_name);
+                        let browsing_context_name = tab_actor.browsing_context();
+                        let browsing_context_actor =
+                            registry.find::<BrowsingContextActor>(&browsing_context_name);
+                        browsing_context_actor.simulate_color_scheme(theme)?;
+                    } else {
+                        warn!("No active tab for updateConfiguration");
+                    }
+                }
                 let msg = EmptyReplyMsg { from: self.name() };
                 let _ = stream.write_json_packet(&msg);
                 ActorMessageStatus::Processed
@@ -69,7 +97,7 @@ impl TargetConfigurationActor {
             configuration: HashMap::new(),
             supported_options: HashMap::from([
                 ("cacheDisabled", false),
-                ("colorSchemeSimulation", false),
+                ("colorSchemeSimulation", true),
                 ("customFormatters", false),
                 ("customUserAgent", false),
                 ("javascriptEnabled", false),
diff --git a/components/shared/embedder/lib.rs b/components/shared/embedder/lib.rs
index 85dd4bf3af9..529ae465567 100644
--- a/components/shared/embedder/lib.rs
+++ b/components/shared/embedder/lib.rs
@@ -293,7 +293,7 @@ pub enum EmbedderMsg {
     AllowOpeningWebView(WebViewId, IpcSender<Option<(WebViewId, ViewportDetails)>>),
     /// A webview was destroyed.
     WebViewClosed(WebViewId),
-    /// A webview gained focus for keyboard events.
+    /// A webview gained focus for keyboard events
     WebViewFocused(WebViewId),
     /// All webviews lost focus for keyboard events.
     WebViewBlurred,