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>

ports/servoshell/desktop/cli.rs

@@ -2,16 +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::{env, panic, process};
-
-use getopts::Options;
-use log::error;
-use servo::config::opts::{self, ArgumentParsingResult};
-use servo::servo_config::pref;
+use std::{env, panic};
 
 use crate::desktop::app::App;
 use crate::desktop::events_loop::EventsLoop;
 use crate::panic_hook;
+use crate::prefs::{parse_command_line_arguments, ArgumentParsingResult};
 
 pub fn main() {
     crate::crash_handler::install();
@@ -19,98 +15,23 @@ pub fn main() {
     crate::init_crypto();
     crate::resources::init();
 
-    // Parse the command line options and store them globally
-    let args: Vec<String> = env::args().collect();
-    let mut opts = Options::new();
-    opts.optflag(
-        "",
-        "clean-shutdown",
-        "Do not shutdown until all threads have finished (macos only)",
-    );
-    opts.optflag("b", "no-native-titlebar", "Do not use native titlebar");
-    opts.optopt("", "device-pixel-ratio", "Device pixels per px", "");
-    opts.optopt(
-        "u",
-        "user-agent",
-        "Set custom user agent string (or ios / android / desktop for platform default)",
-        "NCSA Mosaic/1.0 (X11;SunOS 4.1.4 sun4m)",
-    );
-    opts.optmulti(
-        "",
-        "pref",
-        "A preference to set to enable",
-        "dom.bluetooth.enabled",
-    );
-    opts.optmulti(
-        "",
-        "pref",
-        "A preference to set to disable",
-        "dom.webgpu.enabled=false",
-    );
-    opts.optmulti(
-        "",
-        "prefs-file",
-        "Load in additional prefs from a file.",
-        "--prefs-file /path/to/prefs.json",
-    );
-
-    let opts_matches;
-    let content_process_token;
-
-    match opts::from_cmdline_args(opts, &args) {
-        ArgumentParsingResult::ContentProcess(matches, token) => {
-            opts_matches = matches;
-            content_process_token = Some(token);
-        },
-        ArgumentParsingResult::ChromeProcess(matches) => {
-            opts_matches = matches;
-            content_process_token = None;
-        },
-    };
-
-    crate::prefs::register_user_prefs(&opts_matches);
-
     // TODO: once log-panics is released, can this be replaced by
     // log_panics::init()?
     panic::set_hook(Box::new(panic_hook::panic_hook));
 
-    if let Some(token) = content_process_token {
-        return servo::run_content_process(token);
-    }
-
-    if opts::get().is_printing_version {
-        println!("{}", crate::servo_version());
-        process::exit(0);
-    }
-
-    let clean_shutdown = opts_matches.opt_present("clean-shutdown");
-    let do_not_use_native_titlebar =
-        opts_matches.opt_present("no-native-titlebar") || !(pref!(shell.native_titlebar.enabled));
-    let device_pixel_ratio_override = opts_matches.opt_str("device-pixel-ratio").map(|dppx_str| {
-        dppx_str.parse().unwrap_or_else(|err| {
-            error!("Error parsing option: --device-pixel-ratio ({})", err);
-            process::exit(1);
-        })
-    });
-
-    let user_agent = opts_matches.opt_str("u");
-
-    let url_opt = if !opts_matches.free.is_empty() {
-        Some(&opts_matches.free[0][..])
-    } else {
-        None
+    let args = env::args().collect();
+    let (opts, preferences, servoshell_preferences) = match parse_command_line_arguments(args) {
+        ArgumentParsingResult::ContentProcess(token) => return servo::run_content_process(token),
+        ArgumentParsingResult::ChromeProcess(opts, preferences, servoshell_preferences) => {
+            (opts, preferences, servoshell_preferences)
+        },
     };
 
-    let event_loop = EventsLoop::new(opts::get().headless, opts::get().output_file.is_some())
+    let clean_shutdown = servoshell_preferences.clean_shutdown;
+    let event_loop = EventsLoop::new(opts.headless, opts.output_file.is_some())
         .expect("Failed to create events loop");
 
-    let mut app = App::new(
-        &event_loop,
-        user_agent,
-        url_opt.map(|s| s.to_string()),
-        do_not_use_native_titlebar,
-        device_pixel_ratio_override,
-    );
+    let mut app = App::new(opts, preferences, servoshell_preferences, &event_loop);
 
     event_loop.run_app(&mut app);