Add support for generating dummy DeviceIDs and WindowIDs (#738)

* Add support for generating dummy DeviceIDs and WindowIDs

* Fix linux

* Improve docs and move dummy to unsafe

* Strengthen guarantees a bit

* Add backticks to CHANGELOG.md

Co-Authored-By: Xaeroxe <xaeroxe@amethyst-engine.org>

src/platform/android/mod.rs

@@ -170,9 +170,21 @@ impl EventsLoopProxy {
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct WindowId;
 
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        WindowId
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct DeviceId;
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId
+    }
+}
+
 pub struct Window {
     native_window: *const c_void,
 }

src/platform/emscripten/mod.rs

@@ -27,6 +27,12 @@ unsafe impl Sync for PlatformSpecificWindowBuilderAttributes {}
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct DeviceId;
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId
+    }
+}
+
 #[derive(Clone, Default)]
 pub struct PlatformSpecificHeadlessBuilderAttributes;
 
@@ -149,6 +155,12 @@ impl EventsLoop {
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct WindowId(usize);
 
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        WindowId(0)
+    }
+}
+
 pub struct Window2 {
     cursor_grabbed: Mutex<bool>,
     cursor_hidden: Mutex<bool>,

src/platform/ios/mod.rs

@@ -290,9 +290,21 @@ impl EventsLoopProxy {
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct WindowId;
 
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        WindowId
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct DeviceId;
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId
+    }
+}
+
 #[derive(Clone)]
 pub struct PlatformSpecificWindowBuilderAttributes {
     pub root_view_class: &'static Class,

src/platform/linux/mod.rs

@@ -66,12 +66,24 @@ pub enum WindowId {
     Wayland(wayland::WindowId),
 }
 
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        WindowId::X(x11::WindowId::dummy())
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub enum DeviceId {
     X(x11::DeviceId),
     Wayland(wayland::DeviceId),
 }
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId::X(x11::DeviceId::dummy())
+    }
+}
+
 #[derive(Debug, Clone)]
 pub enum MonitorId {
     X(x11::MonitorId),

src/platform/linux/wayland/mod.rs

@@ -16,9 +16,21 @@ mod window;
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct DeviceId;
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct WindowId(usize);
 
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        WindowId(0)
+    }
+}
+
 #[inline]
 fn make_wid(s: &Proxy<wl_surface::WlSurface>) -> WindowId {
     WindowId(s.c_ptr() as usize)

src/platform/linux/x11/mod.rs

@@ -1262,9 +1262,21 @@ impl<'a> Deref for DeviceInfo<'a> {
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct WindowId(ffi::Window);
 
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        WindowId(0)
+    }
+}
+
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct DeviceId(c_int);
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId(0)
+    }
+}
+
 pub struct Window(Arc<UnownedWindow>);
 
 impl Deref for Window {

src/platform/macos/mod.rs

@@ -8,6 +8,12 @@ use std::sync::Arc;
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct DeviceId;
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId
+    }
+}
+
 use {CreationError};
 
 pub struct Window {

src/platform/macos/window.rs

@@ -50,6 +50,12 @@ use window::MonitorId as RootMonitorId;
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct Id(pub usize);
 
+impl Id {
+    pub unsafe fn dummy() -> Self {
+        Id(0)
+    }
+}
+
 // TODO: It's possible for delegate methods to be called asynchronously, causing data races / `RefCell` panics.
 pub struct DelegateState {
     view: IdRef,

src/platform/windows/mod.rs

@@ -26,6 +26,12 @@ unsafe impl Sync for Cursor {}
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub struct DeviceId(u32);
 
+impl DeviceId {
+    pub unsafe fn dummy() -> Self {
+        DeviceId(0)
+    }
+}
+
 impl DeviceId {
     pub fn get_persistent_identifier(&self) -> Option<String> {
         if self.0 != 0 {
@@ -48,6 +54,14 @@ pub struct WindowId(HWND);
 unsafe impl Send for WindowId {}
 unsafe impl Sync for WindowId {}
 
+impl WindowId {
+    pub unsafe fn dummy() -> Self {
+        use std::ptr::null_mut;
+
+        WindowId(null_mut())
+    }
+}
+
 mod dpi;
 mod drop_handler;
 mod event;