api: Flatten and simplify Servo preferences (#34966)

Flatten and simplify Servo's preferences code. In addition, have both
preferences and options passed in as arguments to `Servo::new()` and
make sure not to use the globally set preferences in `servoshell` (as
much as possible now).

Instead of a complex procedural macro to generate preferences, just
expose a very simple derive macro that adds string based getters and
setters.

- All command-line parsing is moved to servoshell.
- There is no longer the concept of a missing preference.
- Preferences no longer have to be part of the resources bundle because
  they now have reasonable default values.
- servoshell specific preferences are no longer part of the preferences
  exposed by the Servo API.

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

components/constellation/constellation.rs

@@ -660,7 +660,7 @@ where
                 // a dedicated per-process hang monitor will be initialized later inside the content process.
                 // See run_content_process in servo/lib.rs
                 let (background_monitor_register, background_hang_monitor_control_ipc_senders) =
-                    if opts::multiprocess() {
+                    if opts::get().multiprocess {
                         (None, vec![])
                     } else {
                         let (
@@ -2502,7 +2502,7 @@ where
                 };
                 let content = ServiceWorkerUnprivilegedContent::new(sw_senders, origin);
 
-                if opts::multiprocess() {
+                if opts::get().multiprocess {
                     if content.spawn_multiprocess().is_err() {
                         return warn!("Failed to spawn process for SW manager.");
                     }
@@ -5034,7 +5034,7 @@ where
         let pipelines_to_evict = {
             let session_history = self.get_joint_session_history(top_level_browsing_context_id);
 
-            let history_length = pref!(session_history.max_length) as usize;
+            let history_length = pref!(session_history_max_length) as usize;
 
             // The past is stored with older entries at the front.
             // We reverse the iter so that newer entries are at the front and then

components/constellation/pipeline.rs

@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use std::borrow::Cow;
-use std::collections::{HashMap, HashSet};
+use std::collections::HashSet;
 use std::rc::Rc;
 use std::sync::Arc;
 
@@ -39,8 +39,7 @@ use script_traits::{
 };
 use serde::{Deserialize, Serialize};
 use servo_config::opts::{self, Opts};
-use servo_config::prefs;
-use servo_config::prefs::PrefValue;
+use servo_config::prefs::{self, Preferences};
 use servo_url::ServoUrl;
 use webrender_api::DocumentId;
 use webrender_traits::CrossProcessCompositorApi;
@@ -283,7 +282,7 @@ impl Pipeline {
                     load_data: state.load_data.clone(),
                     script_port,
                     opts: (*opts::get()).clone(),
-                    prefs: prefs::pref_map().iter().collect(),
+                    prefs: Box::new(prefs::get().clone()),
                     pipeline_namespace_id: state.pipeline_namespace_id,
                     webrender_document: state.webrender_document,
                     cross_process_compositor_api: state
@@ -300,7 +299,7 @@ impl Pipeline {
                 // Spawn the child process.
                 //
                 // Yes, that's all there is to it!
-                let bhm_control_chan = if opts::multiprocess() {
+                let bhm_control_chan = if opts::get().multiprocess {
                     let (bhm_control_chan, bhm_control_port) =
                         ipc::channel().expect("Sampler chan");
                     unprivileged_pipeline_content.bhm_control_port = Some(bhm_control_port);
@@ -490,7 +489,7 @@ pub struct UnprivilegedPipelineContent {
     load_data: LoadData,
     script_port: IpcReceiver<ConstellationControlMsg>,
     opts: Opts,
-    prefs: HashMap<String, PrefValue>,
+    prefs: Box<Preferences>,
     pipeline_namespace_id: PipelineNamespaceId,
     cross_process_compositor_api: CrossProcessCompositorApi,
     webrender_document: DocumentId,
@@ -581,7 +580,7 @@ impl UnprivilegedPipelineContent {
         self.opts.clone()
     }
 
-    pub fn prefs(&self) -> HashMap<String, PrefValue> {
-        self.prefs.clone()
+    pub fn prefs(&self) -> &Preferences {
+        &self.prefs
     }
 }

components/constellation/sandboxing.rs

@@ -2,7 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use std::collections::HashMap;
 #[cfg(not(windows))]
 use std::env;
 use std::ffi::OsStr;
@@ -23,7 +22,7 @@ use gaol::profile::{Operation, PathPattern, Profile};
 use ipc_channel::Error;
 use serde::{Deserialize, Serialize};
 use servo_config::opts::Opts;
-use servo_config::prefs::PrefValue;
+use servo_config::prefs::Preferences;
 
 use crate::pipeline::UnprivilegedPipelineContent;
 use crate::serviceworker::ServiceWorkerUnprivilegedContent;
@@ -43,7 +42,7 @@ impl UnprivilegedContent {
         }
     }
 
-    pub fn prefs(&self) -> HashMap<String, PrefValue> {
+    pub fn prefs(&self) -> &Preferences {
         match self {
             UnprivilegedContent::Pipeline(content) => content.prefs(),
             UnprivilegedContent::ServiceWorker(content) => content.prefs(),

components/constellation/serviceworker.rs

@@ -2,13 +2,12 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use std::collections::HashMap;
-
 use ipc_channel::Error;
 use script_traits::{SWManagerSenders, ServiceWorkerManagerFactory};
 use serde::{Deserialize, Serialize};
 use servo_config::opts::{self, Opts};
-use servo_config::prefs::{self, PrefValue};
+use servo_config::prefs;
+use servo_config::prefs::Preferences;
 use servo_url::ImmutableOrigin;
 
 use crate::sandboxing::{spawn_multiprocess, UnprivilegedContent};
@@ -18,7 +17,7 @@ use crate::sandboxing::{spawn_multiprocess, UnprivilegedContent};
 #[derive(Deserialize, Serialize)]
 pub struct ServiceWorkerUnprivilegedContent {
     opts: Opts,
-    prefs: HashMap<String, PrefValue>,
+    prefs: Box<Preferences>,
     senders: SWManagerSenders,
     origin: ImmutableOrigin,
 }
@@ -30,7 +29,7 @@ impl ServiceWorkerUnprivilegedContent {
     ) -> ServiceWorkerUnprivilegedContent {
         ServiceWorkerUnprivilegedContent {
             opts: (*opts::get()).clone(),
-            prefs: prefs::pref_map().iter().collect(),
+            prefs: Box::new(prefs::get().clone()),
             senders,
             origin,
         }
@@ -53,7 +52,7 @@ impl ServiceWorkerUnprivilegedContent {
         self.opts.clone()
     }
 
-    pub fn prefs(&self) -> HashMap<String, PrefValue> {
-        self.prefs.clone()
+    pub fn prefs(&self) -> &Preferences {
+        &self.prefs
     }
 }