feat: Move DeviceId to winit-core

This requires a similar restructuring as with WindowId.

Signed-off-by: John Nunley <dev@notgull.net>

winit-core/src/event.rs

@@ -0,0 +1,36 @@
+//! Incoming notifications from the GUI system.
+
+/// Identifier of an input device.
+///
+/// Whenever you receive an event arising from a particular input device, this event contains a `DeviceId` which
+/// identifies its origin. Note that devices may be virtual (representing an on-screen cursor and keyboard focus) or
+/// physical. Virtual devices typically aggregate inputs from multiple physical devices.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct DeviceId(u64);
+
+impl DeviceId {
+    /// Returns a dummy id, useful for unit testing.
+    ///
+    /// # Safety
+    ///
+    /// The only guarantee made about the return value of this function is that
+    /// it will always be equal to itself and to future values returned by this function.
+    /// No other guarantees are made. This may be equal to a real `DeviceId`.
+    ///
+    /// **Passing this into a winit function will result in undefined behavior.**
+    pub const unsafe fn dummy() -> Self {
+        DeviceId(0)
+    }
+}
+
+impl From<u64> for DeviceId {
+    fn from(value: u64) -> Self {
+        Self(value)
+    }
+}
+
+impl From<DeviceId> for u64 {
+    fn from(value: DeviceId) -> Self {
+        value.0
+    }
+}

winit-core/src/lib.rs

@@ -12,5 +12,6 @@ compile_error! { "no-std and no-alloc usage are not yet supported" }
 
 pub mod dpi;
 pub mod error;
+pub mod event;
 pub mod keyboard;
 pub mod window;