WIP: Provide an implementation for the HasRawWindowHandle trait in Ru…

…st for sixtyfps::Window

RWH is the de-facto standard crate in Rust to express window handles
(and associated windowing system connections). This should be safe to
use in the public API.

This patch implements RWH for the GL backend.

cc #877

internal/backends/gl/Cargo.toml

@@ -51,6 +51,7 @@ ttf-parser = "0.14.0" # Use the same version was femtovg's rustybuzz, to avoid d
 unicode-script = "0.5.3" # Use the same version was femtovg's rustybuzz, to avoid duplicate crates
 usvg = { version= "0.20", optional = true, default-features = false, features = ["text"] }
 winit = { version = "0.26", default-features = false }
+raw-window-handle = { version = "0.4.2" }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 web_sys = { version = "0.3", package = "web-sys", features=["console", "WebGlContextAttributes"] }

internal/backends/gl/glwindow.rs

@@ -683,6 +683,15 @@ impl PlatformWindow for GLWindow {
     fn as_any(&self) -> &dyn std::any::Any {
         self
     }
+
+    fn raw_window_handle(&self) -> Option<raw_window_handle::RawWindowHandle> {
+        use raw_window_handle::HasRawWindowHandle;
+        Some(if let Some(mapped_window) = self.borrow_mapped_window() {
+            mapped_window.opengl_context.window().raw_window_handle()
+        } else {
+            raw_window_handle::RawWindowHandle::Xcb(raw_window_handle::XcbHandle::empty())
+        })
+    }
 }
 
 impl Drop for GLWindow {

internal/backends/qt/Cargo.toml

@@ -32,6 +32,7 @@ euclid = "0.22.1"
 lyon_path = "0.17"
 once_cell = "1"
 pin-weak = "1"
+raw-window-handle = { version = "0.4.2" }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 qttypes = { version = "0.2.5", default-features = false }

internal/backends/qt/qt_window.rs

@@ -1510,6 +1510,10 @@ impl PlatformWindow for QtWindow {
     fn as_any(&self) -> &dyn std::any::Any {
         self
     }
+
+    fn raw_window_handle(&self) -> Option<raw_window_handle::RawWindowHandle> {
+        None
+    }
 }
 
 fn get_font(request: FontRequest) -> QFont {

internal/core/Cargo.toml

@@ -22,7 +22,7 @@ libm = ["num-traits/libm", "euclid/libm"]
 # Allow the viewer to query at runtime information about item types
 rtti = []
 # Use the standard library
-std = ["euclid/std", "once_cell/std", "scoped-tls-hkt", "lyon_path", "lyon_algorithms", "lyon_geom", "lyon_svg", "instant"]
+std = ["euclid/std", "once_cell/std", "scoped-tls-hkt", "lyon_path", "lyon_algorithms", "lyon_geom", "lyon_svg", "instant", "raw-window-handle"]
 # Unsafe feature meaning that there is only one core running and all thread_local are static.
 # You can only enable this feature if you are sure that any API of this crate is only called
 # from a single core, and not in a interrupt or signal handler.
@@ -52,6 +52,7 @@ num-traits = { version = "0.2", default-features = false }
 once_cell = { version = "1.5", default-features = false }
 pin-project = "1"
 pin-weak = { version = "1.1", default-features = false }
+raw-window-handle = { version = "0.4.2", optional = true }
 # Note: the rgb version is extracted in ci.yaml for rustdoc builds
 rgb = "0.8.27"
 scoped-tls-hkt = { version = "0.1", optional = true }

internal/core/api.rs

@@ -134,6 +134,16 @@ impl Window {
     }
 }
 
+#[cfg(feature = "std")]
+unsafe impl raw_window_handle::HasRawWindowHandle for Window {
+    #![allow(unsafe_code)]
+    fn raw_window_handle(&self) -> raw_window_handle::RawWindowHandle {
+        self.0
+            .raw_window_handle()
+            .expect("Current rendering backend does not support RawWindowHandle")
+    }
+}
+
 impl crate::window::WindowHandleAccess for Window {
     fn window_handle(&self) -> &Rc<crate::window::Window> {
         &self.0

internal/core/window.rs

@@ -87,6 +87,12 @@ pub trait PlatformWindow {
 
     /// Return self as any so the backend can upcast
     fn as_any(&self) -> &dyn core::any::Any;
+
+    /// Returns the raw window handle for the given window, if the backend implements that.
+    #[cfg(feature = "std")]
+    fn raw_window_handle(&self) -> Option<raw_window_handle::RawWindowHandle> {
+        None
+    }
 }
 
 struct WindowPropertiesTracker {