servoshell: Move touch event simulation to servoshell (#39352)

This change removes the `DebugOption` (`-Z`) for touch event simulation
and moves the implementation of the feature to servoshell. The resaoning
for this is:

 - This is really a servoshell feature and can be implemented on top of
   the API. This moves more code out of the already too-complicated
   renderer.
 - I would like to consolidate `DebugOptions` into a `ServoLogOptions`
   to collect all options for configuring Servo logging. This requires
   moving away all of the non-logging options.
 - Eventually touch event simulation will be able to reuse the fling
   implementation from servoshell as we are actually simulating touch
   events sent to the `WebView`.

Testing: This changes a conditional feature that's used for manual
debugging.
It is difficult to write tests for this as there are no servoshell tests
that
verify input handling.

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

components/compositing/compositor.rs

@@ -117,9 +117,6 @@ pub struct ServoRenderer {
     /// Some XR devices want to run on the main thread.
     webxr_main_thread: webxr::MainThreadRegistry,
 
-    /// True to translate mouse input into touch events.
-    pub(crate) convert_mouse_to_touch: bool,
-
     /// The last position in the rendered view that the mouse moved over. This becomes `None`
     /// when the mouse leaves the rendered view.
     pub(crate) last_mouse_move_position: Option<DevicePoint>,
@@ -306,7 +303,7 @@ impl ServoRenderer {
 }
 
 impl IOCompositor {
-    pub fn new(state: InitialCompositorState, convert_mouse_to_touch: bool) -> Self {
+    pub fn new(state: InitialCompositorState) -> Self {
         let registration = state.mem_profiler_chan.prepare_memory_reporting(
             "compositor".into(),
             state.sender.clone(),
@@ -327,7 +324,6 @@ impl IOCompositor {
                 webrender_gl: state.webrender_gl,
                 #[cfg(feature = "webxr")]
                 webxr_main_thread: state.webxr_main_thread,
-                convert_mouse_to_touch,
                 last_mouse_move_position: None,
                 frame_delayer: Default::default(),
             })),

components/compositing/touch.rs

@@ -283,10 +283,6 @@ impl TouchHandler {
         debug_assert!(old.is_some(), "Sequence already removed?");
     }
 
-    pub fn try_get_current_touch_sequence(&self) -> Option<&TouchSequenceInfo> {
-        self.touch_sequence_map.get(&self.current_sequence_id)
-    }
-
     pub fn get_current_touch_sequence_mut(&mut self) -> &mut TouchSequenceInfo {
         self.touch_sequence_map
             .get_mut(&self.current_sequence_id)

components/compositing/webview_renderer.rs

@@ -16,7 +16,7 @@ use constellation_traits::{EmbedderToConstellationMessage, WindowSizeType};
 use embedder_traits::{
     AnimationState, CompositorHitTestResult, InputEvent, MouseButton, MouseButtonAction,
     MouseButtonEvent, MouseMoveEvent, ScrollEvent as EmbedderScrollEvent, ShutdownState,
-    TouchEvent, TouchEventResult, TouchEventType, TouchId, ViewportDetails,
+    TouchEvent, TouchEventResult, TouchEventType, ViewportDetails,
 };
 use euclid::{Point2D, Scale, Vector2D};
 use log::{debug, warn};
@@ -365,62 +365,6 @@ impl WebViewRenderer {
             return;
         }
 
-        if self.global.borrow().convert_mouse_to_touch {
-            match event {
-                InputEvent::MouseButton(event) => {
-                    match (event.button, event.action) {
-                        (MouseButton::Left, MouseButtonAction::Down) => self.on_touch_down(
-                            TouchEvent::new(TouchEventType::Down, TouchId(0), event.point),
-                        ),
-                        (MouseButton::Left, MouseButtonAction::Up) => self.on_touch_up(
-                            TouchEvent::new(TouchEventType::Up, TouchId(0), event.point),
-                        ),
-                        _ => {},
-                    }
-                    return;
-                },
-                InputEvent::MouseMove(event) => {
-                    if let Some(state) = self.touch_handler.try_get_current_touch_sequence() {
-                        // We assume that the debug option `-Z convert-mouse-to-touch` will only
-                        // be used on devices without native touch input, so we can directly
-                        // reuse the touch handler for tracking the state of pressed buttons.
-                        match state.state {
-                            TouchSequenceState::Touching | TouchSequenceState::Panning { .. } => {
-                                self.on_touch_move(TouchEvent::new(
-                                    TouchEventType::Move,
-                                    TouchId(0),
-                                    event.point,
-                                ));
-                            },
-                            TouchSequenceState::MultiTouch => {
-                                // Multitouch simulation currently is not implemented.
-                                // Since we only get one mouse move event, we would need to
-                                // dispatch one mouse move event per currently pressed mouse button.
-                            },
-                            TouchSequenceState::Pinching => {
-                                // We only have one mouse button, so Pinching should be impossible.
-                                #[cfg(debug_assertions)]
-                                log::error!(
-                                    "Touch handler is in Pinching state, which should be unreachable with \
-                                -Z convert-mouse-to-touch debug option."
-                                );
-                            },
-                            TouchSequenceState::PendingFling { .. } |
-                            TouchSequenceState::Flinging { .. } |
-                            TouchSequenceState::PendingClick(_) |
-                            TouchSequenceState::Finished => {
-                                // Mouse movement without a button being pressed is not
-                                // translated to touch events.
-                            },
-                        }
-                    }
-                    // We don't want to (directly) dispatch mouse events when simulating touch input.
-                    return;
-                },
-                _ => {},
-            }
-        }
-
         self.dispatch_input_event_with_hit_testing(event);
     }
 

components/config/opts.rs

@@ -128,9 +128,6 @@ pub struct DebugOptions {
     /// Whether to show in stdout style sharing cache stats after a restyle.
     pub dump_style_statistics: bool,
 
-    /// Translate mouse input into touch events.
-    pub convert_mouse_to_touch: bool,
-
     /// Log GC passes and their durations.
     pub gc_profile: bool,
 }
@@ -140,7 +137,6 @@ impl DebugOptions {
         for option in debug_string.split(',') {
             match option {
                 "help" => self.help = true,
-                "convert-mouse-to-touch" => self.convert_mouse_to_touch = true,
                 "disable-share-style-cache" => self.disable_share_style_cache = true,
                 "dump-display-list" => self.dump_display_list = true,
                 "dump-stacking-context-tree" => self.dump_stacking_context_tree = true,

components/servo/lib.rs

@@ -463,25 +463,22 @@ impl Servo {
         // The compositor coordinates with the client window to create the final
         // rendered page and display it somewhere.
         let shutdown_state = Rc::new(Cell::new(ShutdownState::NotShuttingDown));
-        let compositor = IOCompositor::new(
-            InitialCompositorState {
-                sender: compositor_proxy,
-                receiver: compositor_receiver,
-                constellation_chan: constellation_chan.clone(),
-                time_profiler_chan,
-                mem_profiler_chan,
-                webrender,
-                webrender_document,
-                webrender_api,
-                rendering_context,
-                webrender_gl,
-                #[cfg(feature = "webxr")]
-                webxr_main_thread,
-                shutdown_state: shutdown_state.clone(),
-                event_loop_waker,
-            },
-            opts.debug.convert_mouse_to_touch,
-        );
+        let compositor = IOCompositor::new(InitialCompositorState {
+            sender: compositor_proxy,
+            receiver: compositor_receiver,
+            constellation_chan: constellation_chan.clone(),
+            time_profiler_chan,
+            mem_profiler_chan,
+            webrender,
+            webrender_document,
+            webrender_api,
+            rendering_context,
+            webrender_gl,
+            #[cfg(feature = "webxr")]
+            webxr_main_thread,
+            shutdown_state: shutdown_state.clone(),
+            event_loop_waker,
+        });
 
         let constellation_proxy = ConstellationProxy::new(constellation_chan);
         Self {

ports/servoshell/desktop/headed_window.rs

@@ -79,6 +79,9 @@ pub struct Window {
     /// the target of egui rendering and also where Servo rendering results are finally
     /// blitted.
     window_rendering_context: Rc<WindowRenderingContext>,
+    /// A helper that simulates touch events when the `--simulate-touch-events` flag
+    /// is enabled.
+    touch_event_simulator: Option<TouchEventSimulator>,
     // Keep this as the last field of the struct to ensure that the rendering context is
     // dropped first.
     // (https://github.com/servo/servo/issues/36711)
@@ -179,6 +182,9 @@ impl Window {
             modifiers_state: Cell::new(ModifiersState::empty()),
             toolbar_height: Cell::new(Default::default()),
             window_rendering_context,
+            touch_event_simulator: servoshell_preferences
+                .simulate_touch_events
+                .then(Default::default),
             rendering_context,
         }
     }
@@ -275,7 +281,29 @@ impl Window {
     }
 
     /// Helper function to handle a click
-    fn handle_mouse(&self, webview: &WebView, button: MouseButton, action: ElementState) {
+    fn handle_mouse_button_event(
+        &self,
+        webview: &WebView,
+        button: MouseButton,
+        action: ElementState,
+    ) {
+        // `point` can be outside viewport, such as at toolbar with negative y-coordinate.
+        let point = self.webview_relative_mouse_point.get();
+        if !webview.rect().contains(point) {
+            return;
+        }
+
+        if self
+            .touch_event_simulator
+            .as_ref()
+            .is_some_and(|touch_event_simulator| {
+                touch_event_simulator
+                    .maybe_consume_move_button_event(webview, button, action, point)
+            })
+        {
+            return;
+        }
+
         let mouse_button = match &button {
             MouseButton::Left => ServoMouseButton::Left,
             MouseButton::Right => ServoMouseButton::Right,
@@ -285,11 +313,6 @@ impl Window {
             MouseButton::Other(value) => ServoMouseButton::Other(*value),
         };
 
-        let point = self.webview_relative_mouse_point.get();
-        // `point` can be outside viewport, such as at toolbar with negative y-coordinate.
-        if !webview.rect().contains(point) {
-            return;
-        }
         let action = match action {
             ElementState::Pressed => MouseButtonAction::Down,
             ElementState::Released => MouseButtonAction::Up,
@@ -302,6 +325,36 @@ impl Window {
         )));
     }
 
+    /// Helper function to handle mouse move events.
+    fn handle_mouse_move_event(&self, webview: &WebView, position: PhysicalPosition<f64>) {
+        let mut point = winit_position_to_euclid_point(position).to_f32();
+        point.y -= (self.toolbar_height() * self.hidpi_scale_factor()).0;
+
+        let previous_point = self.webview_relative_mouse_point.get();
+        self.webview_relative_mouse_point.set(point);
+
+        if !webview.rect().contains(point) {
+            if webview.rect().contains(previous_point) {
+                webview.notify_input_event(InputEvent::MouseLeftViewport(
+                    MouseLeftViewportEvent::default(),
+                ));
+            }
+            return;
+        }
+
+        if self
+            .touch_event_simulator
+            .as_ref()
+            .is_some_and(|touch_event_simulator| {
+                touch_event_simulator.maybe_consume_mouse_move_event(webview, point)
+            })
+        {
+            return;
+        }
+
+        webview.notify_input_event(InputEvent::MouseMove(MouseMoveEvent::new(point)));
+    }
+
     /// Handle key events before sending them to Servo.
     fn handle_intercepted_key_bindings(
         &self,
@@ -623,22 +676,10 @@ impl WindowPortsMethods for Window {
             WindowEvent::KeyboardInput { event, .. } => self.handle_keyboard_input(state, event),
             WindowEvent::ModifiersChanged(modifiers) => self.modifiers_state.set(modifiers.state()),
             WindowEvent::MouseInput { state, button, .. } => {
-                self.handle_mouse(&webview, button, state);
+                self.handle_mouse_button_event(&webview, button, state);
             },
             WindowEvent::CursorMoved { position, .. } => {
-                let mut point = winit_position_to_euclid_point(position).to_f32();
-                point.y -= (self.toolbar_height() * self.hidpi_scale_factor()).0;
-
-                let previous_point = self.webview_relative_mouse_point.get();
-                if webview.rect().contains(point) {
-                    webview.notify_input_event(InputEvent::MouseMove(MouseMoveEvent::new(point)));
-                } else if webview.rect().contains(previous_point) {
-                    webview.notify_input_event(InputEvent::MouseLeftViewport(
-                        MouseLeftViewportEvent::default(),
-                    ));
-                }
-
-                self.webview_relative_mouse_point.set(point);
+                self.handle_mouse_move_event(&webview, position);
             },
             WindowEvent::CursorLeft { .. } => {
                 if webview
@@ -967,3 +1008,57 @@ impl XRWindowPose {
         self.xr_rotation.set(rotation);
     }
 }
+
+#[derive(Default)]
+pub struct TouchEventSimulator {
+    pub left_mouse_button_down: Cell<bool>,
+}
+
+impl TouchEventSimulator {
+    fn maybe_consume_move_button_event(
+        &self,
+        webview: &WebView,
+        button: MouseButton,
+        action: ElementState,
+        point: Point2D<f32, DevicePixel>,
+    ) -> bool {
+        if button != MouseButton::Left {
+            return false;
+        }
+
+        if action == ElementState::Pressed && !self.left_mouse_button_down.get() {
+            webview.notify_input_event(InputEvent::Touch(TouchEvent::new(
+                TouchEventType::Down,
+                TouchId(0),
+                point,
+            )));
+            self.left_mouse_button_down.set(true);
+        } else if action == ElementState::Released {
+            webview.notify_input_event(InputEvent::Touch(TouchEvent::new(
+                TouchEventType::Up,
+                TouchId(0),
+                point,
+            )));
+            self.left_mouse_button_down.set(false);
+        }
+
+        true
+    }
+
+    fn maybe_consume_mouse_move_event(
+        &self,
+        webview: &WebView,
+        point: Point2D<f32, DevicePixel>,
+    ) -> bool {
+        if !self.left_mouse_button_down.get() {
+            return false;
+        }
+
+        webview.notify_input_event(InputEvent::Touch(TouchEvent::new(
+            TouchEventType::Move,
+            TouchId(0),
+            point,
+        )));
+        true
+    }
+}

ports/servoshell/prefs.rs

@@ -71,6 +71,8 @@ pub(crate) struct ServoShellPreferences {
     /// An override for the screen resolution. This is useful for testing behavior on different screen sizes,
     /// such as the screen of a mobile device.
     pub screen_size_override: Option<Size2D<u32, DeviceIndependentPixel>>,
+    /// Whether or not to simulate touch events using mouse events.
+    pub simulate_touch_events: bool,
     /// If not-None, the path to a file to output the default WebView's rendered output
     /// after waiting for a stable image, this implies `Self::exit_after_load`.
     pub output_image_path: Option<String>,
@@ -82,15 +84,12 @@ pub(crate) struct ServoShellPreferences {
     /// `None` to disable WebDriver or `Some` with a port number to start a server to listen to
     /// remote WebDriver commands.
     pub webdriver_port: Option<u16>,
-
     /// Whether the CLI option to enable experimental prefs was present at startup.
     pub experimental_prefs_enabled: bool,
-
     /// Log filter given in the `log_filter` spec as a String, if any.
     /// If a filter is passed, the logger should adjust accordingly.
     #[cfg(target_env = "ohos")]
     pub log_filter: Option<String>,
-
     /// Log also to a file
     #[cfg(target_env = "ohos")]
     pub log_to_file: bool,
@@ -106,6 +105,7 @@ impl Default for ServoShellPreferences {
             initial_window_size: Size2D::new(1024, 740),
             no_native_titlebar: true,
             screen_size_override: None,
+            simulate_touch_events: false,
             searchpage: "https://duckduckgo.com/html/?q=%s".into(),
             tracing_filter: None,
             url: None,
@@ -505,6 +505,11 @@ struct CmdArgs {
         parse(parse_resolution_string), fallback(None))]
     screen_size_override: Option<Size2D<u32, DeviceIndependentPixel>>,
 
+    /// Use mouse events to simulate touch events. Left button presses will be converted to touch
+    /// and mouse movements while the left button is pressed will be converted to touch movements.
+    #[bpaf(long("simulate-touch-events"))]
+    simulate_touch_events: bool,
+
     /// Define a custom filter for traces. Overrides `SERVO_TRACING` if set.
     #[bpaf(long("tracing-filter"), argument("FILTER"))]
     tracing_filter: Option<String>,
@@ -663,6 +668,7 @@ pub(crate) fn parse_command_line_arguments(args: Vec<String>) -> ArgumentParsing
         tracing_filter: cmd_args.tracing_filter,
         initial_window_size: cmd_args.window_size.unwrap_or(default_window_size),
         screen_size_override: cmd_args.screen_size_override,
+        simulate_touch_events: cmd_args.simulate_touch_events,
         webdriver_port: cmd_args.webdriver_port,
         output_image_path: cmd_args.output.map(|p| p.to_string_lossy().into_owned()),
         exit_after_stable_image: cmd_args.exit,
@@ -728,10 +734,6 @@ fn print_debug_options_usage(app: &str) {
         "Usage: {} debug option,[options,...]\n\twhere options include\n\nOptions:",
         app
     );
-    print_option(
-        "convert-mouse-to-touch",
-        "Send touch events instead of mouse events",
-    );
     print_option(
         "disable-share-style-cache",
         "Disable the style sharing cache.",