On Web, add Window::(set_)prevent_default() (#3307)

CHANGELOG.md

@@ -23,6 +23,7 @@ Unreleased` header.
 - **Breaking:** On Web, return `RawWindowHandle::WebCanvas` instead of `RawWindowHandle::Web`.
 - **Breaking:** On Web, macOS and iOS, return `HandleError::Unavailable` when a window handle is not available.
 - **Breaking:** Bump MSRV from `1.65` to `1.70`.
+- On Web, add the ability to toggle calling `Event.preventDefault()` on `Window`.
 
 # 0.29.6
 

src/platform/web.rs

@@ -42,6 +42,21 @@ pub trait WindowExtWebSys {
     /// Only returns the canvas if called from inside the window context (the
     /// main thread).
     fn canvas(&self) -> Option<HtmlCanvasElement>;
+
+    /// Returns [`true`] if calling `event.preventDefault()` is enabled.
+    ///
+    /// See [`Window::set_prevent_default()`] for more details.
+    fn prevent_default(&self) -> bool;
+
+    /// Sets whether `event.preventDefault()` should be called on events on the
+    /// canvas that have side effects.
+    ///
+    /// For example, by default using the mouse wheel would cause the page to scroll, enabling this
+    /// would prevent that.
+    ///
+    /// Some events are impossible to prevent. E.g. Firefox allows to access the native browser
+    /// context menu with Shift+Rightclick.
+    fn set_prevent_default(&self, prevent_default: bool);
 }
 
 impl WindowExtWebSys for Window {
@@ -49,6 +64,14 @@ impl WindowExtWebSys for Window {
     fn canvas(&self) -> Option<HtmlCanvasElement> {
         self.window.canvas()
     }
+
+    fn prevent_default(&self) -> bool {
+        self.window.prevent_default()
+    }
+
+    fn set_prevent_default(&self, prevent_default: bool) {
+        self.window.set_prevent_default(prevent_default)
+    }
 }
 
 pub trait WindowBuilderExtWebSys {
@@ -60,14 +83,10 @@ pub trait WindowBuilderExtWebSys {
     /// [`None`] by default.
     fn with_canvas(self, canvas: Option<HtmlCanvasElement>) -> Self;
 
-    /// Whether `event.preventDefault()` should be called on events on the
+    /// Sets whether `event.preventDefault()` should be called on events on the
     /// canvas that have side effects.
     ///
-    /// For example, by default using the mouse wheel would cause the page to scroll, enabling this
+    /// See [`Window::set_prevent_default()`] for more details.
-    /// would prevent that.
-    ///
-    /// Some events are impossible to prevent. E.g. Firefox allows to access the native browser
-    /// context menu with Shift+Rightclick.
     ///
     /// Enabled by default.
     fn with_prevent_default(self, prevent_default: bool) -> Self;

src/platform_impl/web/event_loop/window_target.rs

@@ -75,18 +75,13 @@ impl<T> EventLoopWindowTarget<T> {
         WindowId(self.runner.generate_id())
     }
 
-    pub fn register(
+    pub fn register(&self, canvas: &Rc<RefCell<backend::Canvas>>, id: WindowId) {
-        &self,
-        canvas: &Rc<RefCell<backend::Canvas>>,
-        id: WindowId,
-        prevent_default: bool,
-    ) {
         let canvas_clone = canvas.clone();
         let mut canvas = canvas.borrow_mut();
         #[cfg(any(feature = "rwh_04", feature = "rwh_05"))]
         canvas.set_attribute("data-raw-handle", &id.0.to_string());
 
-        canvas.on_touch_start(prevent_default);
+        canvas.on_touch_start();
 
         let runner = self.runner.clone();
         let has_focus = canvas.has_focus.clone();
@@ -157,7 +152,6 @@ impl<T> EventLoopWindowTarget<T> {
                     .chain(modifiers_changed),
                 );
             },
-            prevent_default,
         );
 
         let runner = self.runner.clone();
@@ -194,7 +188,6 @@ impl<T> EventLoopWindowTarget<T> {
                     .chain(modifiers_changed),
                 )
             },
-            prevent_default,
         );
 
         let has_focus = canvas.has_focus.clone();
@@ -374,7 +367,6 @@ impl<T> EventLoopWindowTarget<T> {
                     ]));
                 }
             },
-            prevent_default,
         );
 
         canvas.on_mouse_press(
@@ -456,7 +448,6 @@ impl<T> EventLoopWindowTarget<T> {
                     )))
                 }
             },
-            prevent_default,
         );
 
         canvas.on_mouse_release(
@@ -547,30 +538,27 @@ impl<T> EventLoopWindowTarget<T> {
 
         let runner = self.runner.clone();
         let modifiers = self.modifiers.clone();
-        canvas.on_mouse_wheel(
+        canvas.on_mouse_wheel(move |pointer_id, delta, active_modifiers| {
-            move |pointer_id, delta, active_modifiers| {
+            let modifiers_changed =
-                let modifiers_changed = (has_focus.get() && modifiers.get() != active_modifiers)
+                (has_focus.get() && modifiers.get() != active_modifiers).then(|| {
-                    .then(|| {
+                    modifiers.set(active_modifiers);
-                        modifiers.set(active_modifiers);
-                        Event::WindowEvent {
-                            window_id: RootWindowId(id),
-                            event: WindowEvent::ModifiersChanged(active_modifiers.into()),
-                        }
-                    });
-
-                runner.send_events(modifiers_changed.into_iter().chain(iter::once(
                     Event::WindowEvent {
                         window_id: RootWindowId(id),
-                        event: WindowEvent::MouseWheel {
+                        event: WindowEvent::ModifiersChanged(active_modifiers.into()),
-                            device_id: RootDeviceId(DeviceId(pointer_id)),
+                    }
-                            delta,
+                });
-                            phase: TouchPhase::Moved,
+
-                        },
+            runner.send_events(modifiers_changed.into_iter().chain(iter::once(
+                Event::WindowEvent {
+                    window_id: RootWindowId(id),
+                    event: WindowEvent::MouseWheel {
+                        device_id: RootDeviceId(DeviceId(pointer_id)),
+                        delta,
+                        phase: TouchPhase::Moved,
                     },
-                )));
+                },
-            },
+            )));
-            prevent_default,
+        });
-        );
 
         let runner = self.runner.clone();
         canvas.on_touch_cancel(move |device_id, location, force| {
@@ -649,7 +637,7 @@ impl<T> EventLoopWindowTarget<T> {
         let runner = self.runner.clone();
         canvas.on_animation_frame(move || runner.request_redraw(RootWindowId(id)));
 
-        canvas.on_context_menu(prevent_default);
+        canvas.on_context_menu();
     }
 
     pub fn available_monitors(&self) -> VecDequeIter<MonitorHandle> {

src/platform_impl/web/web_sys/canvas.rs

@@ -30,6 +30,7 @@ pub struct Canvas {
     common: Common,
     id: WindowId,
     pub has_focus: Rc<Cell<bool>>,
+    pub prevent_default: Rc<Cell<bool>>,
     pub is_intersecting: Option<bool>,
     on_touch_start: Option<EventListenerHandle<dyn FnMut(Event)>>,
     on_focus: Option<EventListenerHandle<dyn FnMut(FocusEvent)>>,
@@ -141,6 +142,7 @@ impl Canvas {
             common,
             id,
             has_focus: Rc::new(Cell::new(false)),
+            prevent_default: Rc::new(Cell::new(platform_attr.prevent_default)),
             is_intersecting: None,
             on_touch_start: None,
             on_blur: None,
@@ -231,9 +233,10 @@ impl Canvas {
         &self.common.style
     }
 
-    pub fn on_touch_start(&mut self, prevent_default: bool) {
+    pub fn on_touch_start(&mut self) {
+        let prevent_default = Rc::clone(&self.prevent_default);
         self.on_touch_start = Some(self.common.add_event("touchstart", move |event: Event| {
-            if prevent_default {
+            if prevent_default.get() {
                 event.prevent_default();
             }
         }));
@@ -257,13 +260,14 @@ impl Canvas {
         }));
     }
 
-    pub fn on_keyboard_release<F>(&mut self, mut handler: F, prevent_default: bool)
+    pub fn on_keyboard_release<F>(&mut self, mut handler: F)
     where
         F: 'static + FnMut(PhysicalKey, Key, Option<SmolStr>, KeyLocation, bool, ModifiersState),
     {
+        let prevent_default = Rc::clone(&self.prevent_default);
         self.on_keyboard_release =
             Some(self.common.add_event("keyup", move |event: KeyboardEvent| {
-                if prevent_default {
+                if prevent_default.get() {
                     event.prevent_default();
                 }
                 let key = event::key(&event);
@@ -279,14 +283,15 @@ impl Canvas {
             }));
     }
 
-    pub fn on_keyboard_press<F>(&mut self, mut handler: F, prevent_default: bool)
+    pub fn on_keyboard_press<F>(&mut self, mut handler: F)
     where
         F: 'static + FnMut(PhysicalKey, Key, Option<SmolStr>, KeyLocation, bool, ModifiersState),
     {
+        let prevent_default = Rc::clone(&self.prevent_default);
         self.on_keyboard_press = Some(self.common.add_event(
             "keydown",
             move |event: KeyboardEvent| {
-                if prevent_default {
+                if prevent_default.get() {
                     event.prevent_default();
                 }
                 let key = event::key(&event);
@@ -340,7 +345,6 @@ impl Canvas {
         modifier_handler: MOD,
         mouse_handler: M,
         touch_handler: T,
-        prevent_default: bool,
     ) where
         MOD: 'static + FnMut(ModifiersState),
         M: 'static + FnMut(ModifiersState, i32, PhysicalPosition<f64>, MouseButton),
@@ -351,7 +355,7 @@ impl Canvas {
             modifier_handler,
             mouse_handler,
             touch_handler,
-            prevent_default,
+            Rc::clone(&self.prevent_default),
         )
     }
 
@@ -361,7 +365,6 @@ impl Canvas {
         mouse_handler: M,
         touch_handler: T,
         button_handler: B,
-        prevent_default: bool,
     ) where
         MOD: 'static + FnMut(ModifiersState),
         M: 'static + FnMut(ModifiersState, i32, &mut dyn Iterator<Item = PhysicalPosition<f64>>),
@@ -375,7 +378,7 @@ impl Canvas {
             mouse_handler,
             touch_handler,
             button_handler,
-            prevent_default,
+            Rc::clone(&self.prevent_default),
         )
     }
 
@@ -386,13 +389,14 @@ impl Canvas {
         self.pointer_handler.on_touch_cancel(&self.common, handler)
     }
 
-    pub fn on_mouse_wheel<F>(&mut self, mut handler: F, prevent_default: bool)
+    pub fn on_mouse_wheel<F>(&mut self, mut handler: F)
     where
         F: 'static + FnMut(i32, MouseScrollDelta, ModifiersState),
     {
         let window = self.common.window.clone();
+        let prevent_default = Rc::clone(&self.prevent_default);
         self.on_mouse_wheel = Some(self.common.add_event("wheel", move |event: WheelEvent| {
-            if prevent_default {
+            if prevent_default.get() {
                 event.prevent_default();
             }
 
@@ -443,11 +447,12 @@ impl Canvas {
         self.animation_frame_handler.on_animation_frame(f)
     }
 
-    pub(crate) fn on_context_menu(&mut self, prevent_default: bool) {
+    pub(crate) fn on_context_menu(&mut self) {
+        let prevent_default = Rc::clone(&self.prevent_default);
         self.on_context_menu = Some(self.common.add_event(
             "contextmenu",
             move |event: PointerEvent| {
-                if prevent_default {
+                if prevent_default.get() {
                     event.prevent_default();
                 }
             },

src/platform_impl/web/web_sys/pointer.rs

@@ -1,3 +1,6 @@
+use std::cell::Cell;
+use std::rc::Rc;
+
 use super::canvas::Common;
 use super::event;
 use super::event_handle::EventListenerHandle;
@@ -110,7 +113,7 @@ impl PointerHandler {
         mut modifier_handler: MOD,
         mut mouse_handler: M,
         mut touch_handler: T,
-        prevent_default: bool,
+        prevent_default: Rc<Cell<bool>>,
     ) where
         MOD: 'static + FnMut(ModifiersState),
         M: 'static + FnMut(ModifiersState, i32, PhysicalPosition<f64>, MouseButton),
@@ -121,7 +124,7 @@ impl PointerHandler {
         self.on_pointer_press = Some(canvas_common.add_event(
             "pointerdown",
             move |event: PointerEvent| {
-                if prevent_default {
+                if prevent_default.get() {
                     // prevent text selection
                     event.prevent_default();
                     // but still focus element
@@ -165,7 +168,7 @@ impl PointerHandler {
         mut mouse_handler: M,
         mut touch_handler: T,
         mut button_handler: B,
-        prevent_default: bool,
+        prevent_default: Rc<Cell<bool>>,
     ) where
         MOD: 'static + FnMut(ModifiersState),
         M: 'static + FnMut(ModifiersState, i32, &mut dyn Iterator<Item = PhysicalPosition<f64>>),
@@ -197,7 +200,7 @@ impl PointerHandler {
                         "expect pointer type of a chorded button event to be a mouse"
                     );
 
-                    if prevent_default {
+                    if prevent_default.get() {
                         // prevent text selection
                         event.prevent_default();
                         // but still focus element

src/platform_impl/web/window.rs

@@ -36,8 +36,6 @@ impl Window {
     ) -> Result<Self, RootOE> {
         let id = target.generate_id();
 
-        let prevent_default = platform_attr.prevent_default;
-
         let window = target.runner.window();
         let document = target.runner.document();
         let canvas =
@@ -45,7 +43,7 @@ impl Window {
         let canvas = Rc::new(RefCell::new(canvas));
         let cursor = CursorState::new(canvas.borrow().style().clone());
 
-        target.register(&canvas, id, prevent_default);
+        target.register(&canvas, id);
 
         let runner = target.runner.clone();
         let destroy_fn = Box::new(move || runner.notify_destroy_window(RootWI(id)));
@@ -84,6 +82,16 @@ impl Window {
             .map(|inner| inner.canvas.borrow().raw().clone())
     }
 
+    pub(crate) fn prevent_default(&self) -> bool {
+        self.inner
+            .queue(|inner| inner.canvas.borrow().prevent_default.get())
+    }
+
+    pub(crate) fn set_prevent_default(&self, prevent_default: bool) {
+        self.inner
+            .dispatch(move |inner| inner.canvas.borrow().prevent_default.set(prevent_default))
+    }
+
     #[cfg(feature = "rwh_06")]
     #[inline]
     pub fn raw_window_handle_rwh_06(&self) -> Result<rwh_06::RawWindowHandle, rwh_06::HandleError> {