Experimental wgpu WebGL backend support

- Added missing `draw_cache_align_4x4` call for `brush_glyph` on wasm32 target
- Added WebGL support to `integratio_wgpu` example
- Fixed test.yml CI workflow
- Removed spir-v shader in `integration_wgpu`; Fixed formatting
- Removed redundant `BoxStream` typedef

winit/src/clipboard.rs

@@ -6,15 +6,40 @@ use crate::command::{self, Command};
 /// A buffer for short-term storage and transfer within and between
 /// applications.
 #[allow(missing_debug_implementations)]
+#[cfg(target_arch = "wasm32")]
+pub struct Clipboard;
+
+#[cfg(target_arch = "wasm32")]
+impl Clipboard {
+    /// Creates a new [`Clipboard`] for the given window.
+    pub fn connect(_window: &winit::window::Window) -> Clipboard {
+        Clipboard
+    }
+
+    /// Reads the current content of the [`Clipboard`] as text.
+    pub fn read(&self) -> Option<String> {
+        None
+    }
+
+    /// Writes the given text contents to the [`Clipboard`].
+    pub fn write(&mut self, _contents: String) {}
+}
+
+/// A buffer for short-term storage and transfer within and between
+/// applications.
+#[allow(missing_debug_implementations)]
+#[cfg(not(target_arch = "wasm32"))]
 pub struct Clipboard {
     state: State,
 }
 
+#[cfg(not(target_arch = "wasm32"))]
 enum State {
     Connected(window_clipboard::Clipboard),
     Unavailable,
 }
 
+#[cfg(not(target_arch = "wasm32"))]
 impl Clipboard {
     /// Creates a new [`Clipboard`] for the given window.
     pub fn connect(window: &winit::window::Window) -> Clipboard {