Add MouseButton::{Back, Forward} to MouseInput

Add named variants for physical back and forward keys which could
be found on some mice. The macOS bits may not work on all the
hardware given that apple doesn't directly support such a thing.

Co-authored-by: daxpedda <daxpedda@gmail.com>

CHANGELOG.md

@@ -85,6 +85,8 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On Web, fix `DeviceEvent::MouseMotion` only being emitted for each canvas instead of the whole window.
 - On Web, add `DeviceEvent::Motion`, `DeviceEvent::MouseWheel`, `DeviceEvent::Button` and
   `DeviceEvent::Key` support.
+- **Breaking** `MouseButton` now supports `Back` and `Forward` variants, emitted from mouse events
+  on Wayland, X11, Windows, macOS and Web.
 
 # 0.28.6
 

src/event.rs

@@ -1202,12 +1202,19 @@ pub enum ElementState {
 }
 
 /// Describes a button of a mouse controller.
+///
+/// ## Platform-specific
+///
+/// **macOS:** `Back` and `Forward` might not work with all hardware.
+/// **Orbital:** `Back` and `Forward` are unsupported due to orbital not supporting them.
 #[derive(Debug, Hash, PartialEq, Eq, Clone, Copy)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 pub enum MouseButton {
     Left,
     Right,
     Middle,
+    Back,
+    Forward,
     Other(u16),
 }
 

src/platform_impl/linux/wayland/seat/pointer/mod.rs

@@ -397,15 +397,21 @@ impl Default for WinitPointerDataInner {
 
 /// Convert the Wayland button into winit.
 fn wayland_button_to_winit(button: u32) -> MouseButton {
-    // These values are comming from <linux/input-event-codes.h>.
+    // These values are coming from <linux/input-event-codes.h>.
     const BTN_LEFT: u32 = 0x110;
     const BTN_RIGHT: u32 = 0x111;
     const BTN_MIDDLE: u32 = 0x112;
+    const BTN_SIDE: u32 = 0x113;
+    const BTN_EXTRA: u32 = 0x114;
+    const BTN_FORWARD: u32 = 0x115;
+    const BTN_BACK: u32 = 0x116;
 
     match button {
         BTN_LEFT => MouseButton::Left,
         BTN_RIGHT => MouseButton::Right,
         BTN_MIDDLE => MouseButton::Middle,
+        BTN_BACK | BTN_SIDE => MouseButton::Back,
+        BTN_FORWARD | BTN_EXTRA => MouseButton::Forward,
         button => MouseButton::Other(button as u16),
     }
 }

src/platform_impl/linux/x11/event_processor.rs

@@ -579,7 +579,7 @@ impl<T: 'static> EventProcessor<T> {
 
                 use crate::event::{
                     ElementState::{Pressed, Released},
-                    MouseButton::{Left, Middle, Other, Right},
+                    MouseButton::{Back, Forward, Left, Middle, Other, Right},
                     MouseScrollDelta::LineDelta,
                     Touch,
                     WindowEvent::{
@@ -651,6 +651,23 @@ impl<T: 'static> EventProcessor<T> {
                                 }
                             }
 
+                            8 => callback(Event::WindowEvent {
+                                window_id,
+                                event: MouseInput {
+                                    device_id,
+                                    state,
+                                    button: Back,
+                                },
+                            }),
+                            9 => callback(Event::WindowEvent {
+                                window_id,
+                                event: MouseInput {
+                                    device_id,
+                                    state,
+                                    button: Forward,
+                                },
+                            }),
+
                             x => callback(Event::WindowEvent {
                                 window_id,
                                 event: MouseInput {

src/platform_impl/macos/view.rs

@@ -1027,10 +1027,14 @@ fn mouse_button(event: &NSEvent) -> MouseButton {
     // The buttonNumber property only makes sense for the mouse events:
     // NSLeftMouse.../NSRightMouse.../NSOtherMouse...
     // For the other events, it's always set to 0.
+    // MacOS only defines the left, right and middle buttons, 3..=31 are left as generic buttons,
+    // but 3 and 4 are very commonly used as Back and Forward by hardware vendors and applications.
     match event.buttonNumber() {
         0 => MouseButton::Left,
         1 => MouseButton::Right,
         2 => MouseButton::Middle,
+        3 => MouseButton::Back,
+        4 => MouseButton::Forward,
         n => MouseButton::Other(n as u16),
     }
 }

src/platform_impl/web/web_sys/event.rs

@@ -10,11 +10,14 @@ use wasm_bindgen::{JsCast, JsValue};
 use web_sys::{HtmlCanvasElement, KeyboardEvent, MouseEvent, PointerEvent, WheelEvent};
 
 bitflags! {
+    // https://www.w3.org/TR/pointerevents3/#the-buttons-property
     #[derive(Debug, Clone, Copy, PartialEq, Eq)]
     pub struct ButtonsState: u16 {
-        const LEFT   = 0b001;
-        const RIGHT  = 0b010;
-        const MIDDLE = 0b100;
+        const LEFT    = 0b00001;
+        const RIGHT   = 0b00010;
+        const MIDDLE  = 0b00100;
+        const BACK    = 0b01000;
+        const FORWARD = 0b10000;
     }
 }
 
@@ -24,6 +27,8 @@ impl From<ButtonsState> for MouseButton {
             ButtonsState::LEFT => MouseButton::Left,
             ButtonsState::RIGHT => MouseButton::Right,
             ButtonsState::MIDDLE => MouseButton::Middle,
+            ButtonsState::BACK => MouseButton::Back,
+            ButtonsState::FORWARD => MouseButton::Forward,
             _ => MouseButton::Other(value.bits()),
         }
     }
@@ -35,6 +40,8 @@ impl From<MouseButton> for ButtonsState {
             MouseButton::Left => ButtonsState::LEFT,
             MouseButton::Right => ButtonsState::RIGHT,
             MouseButton::Middle => ButtonsState::MIDDLE,
+            MouseButton::Back => ButtonsState::BACK,
+            MouseButton::Forward => ButtonsState::FORWARD,
             MouseButton::Other(value) => ButtonsState::from_bits_retain(value),
         }
     }
@@ -45,11 +52,14 @@ pub fn mouse_buttons(event: &MouseEvent) -> ButtonsState {
 }
 
 pub fn mouse_button(event: &MouseEvent) -> Option<MouseButton> {
+    // https://www.w3.org/TR/pointerevents3/#the-button-property
     match event.button() {
         -1 => None,
         0 => Some(MouseButton::Left),
         1 => Some(MouseButton::Middle),
         2 => Some(MouseButton::Right),
+        3 => Some(MouseButton::Back),
+        4 => Some(MouseButton::Forward),
         i => Some(MouseButton::Other(
             i.try_into()
                 .expect("unexpected negative mouse button value"),
@@ -63,6 +73,8 @@ impl MouseButton {
             MouseButton::Left => 0,
             MouseButton::Right => 1,
             MouseButton::Middle => 2,
+            MouseButton::Back => 3,
+            MouseButton::Forward => 4,
             MouseButton::Other(value) => value.into(),
         }
     }

src/platform_impl/windows/event_loop.rs

@@ -1647,7 +1647,8 @@ unsafe fn public_window_callback_inner<T: 'static>(
 
         WM_XBUTTONDOWN => {
             use crate::event::{
-                ElementState::Pressed, MouseButton::Other, WindowEvent::MouseInput,
+                ElementState::Pressed, MouseButton::Back, MouseButton::Forward, MouseButton::Other,
+                WindowEvent::MouseInput,
             };
             let xbutton = super::get_xbutton_wparam(wparam as u32);
 
@@ -1660,15 +1661,20 @@ unsafe fn public_window_callback_inner<T: 'static>(
                 event: MouseInput {
                     device_id: DEVICE_ID,
                     state: Pressed,
-                    button: Other(xbutton),
+                    button: match xbutton {
+                        1 => Back,
+                        2 => Forward,
+                        _ => Other(xbutton),
+                    },
                 },
             });
             result = ProcResult::Value(0);
         }
 
         WM_XBUTTONUP => {
             use crate::event::{
-                ElementState::Released, MouseButton::Other, WindowEvent::MouseInput,
+                ElementState::Released, MouseButton::Back, MouseButton::Forward,
+                MouseButton::Other, WindowEvent::MouseInput,
             };
             let xbutton = super::get_xbutton_wparam(wparam as u32);
 
@@ -1681,7 +1687,11 @@ unsafe fn public_window_callback_inner<T: 'static>(
                 event: MouseInput {
                     device_id: DEVICE_ID,
                     state: Released,
-                    button: Other(xbutton),
+                    button: match xbutton {
+                        1 => Back,
+                        2 => Forward,
+                        _ => Other(xbutton),
+                    },
                 },
             });
             result = ProcResult::Value(0);