m: Cache document in web frontend (#66)

Author: notgull

src/lib.rs

@@ -93,7 +93,7 @@ make_dispatch! {
     #[cfg(target_os = "macos")]
     CG((), cg::CGImpl),
     #[cfg(target_arch = "wasm32")]
-    Web((), web::WebImpl),
+    Web(web::WebDisplayImpl, web::WebImpl),
     #[cfg(target_os = "redox")]
     Orbital((), orbital::OrbitalImpl),
 }
@@ -134,7 +134,7 @@ impl Context {
             #[cfg(target_os = "macos")]
             RawDisplayHandle::AppKit(_) => ContextDispatch::CG(()),
             #[cfg(target_arch = "wasm32")]
-            RawDisplayHandle::Web(_) => ContextDispatch::Web(()),
+            RawDisplayHandle::Web(_) => ContextDispatch::Web(web::WebDisplayImpl::new()?),
             #[cfg(target_os = "redox")]
             RawDisplayHandle::Orbital(_) => ContextDispatch::Orbital(()),
             unimplemented_display_handle => {
@@ -212,8 +212,8 @@ impl Surface {
                 SurfaceDispatch::CG(unsafe { cg::CGImpl::new(appkit_handle)? })
             }
             #[cfg(target_arch = "wasm32")]
-            (ContextDispatch::Web(()), RawWindowHandle::Web(web_handle)) => {
-                SurfaceDispatch::Web(web::WebImpl::new(web_handle)?)
+            (ContextDispatch::Web(context), RawWindowHandle::Web(web_handle)) => {
+                SurfaceDispatch::Web(web::WebImpl::new(context, web_handle)?)
             }
             #[cfg(target_os = "redox")]
             (ContextDispatch::Orbital(()), RawWindowHandle::Orbital(orbital_handle)) => {

src/web.rs

@@ -7,14 +7,16 @@ use web_sys::ImageData;
 
 use crate::SoftBufferError;
 
-pub struct WebImpl {
-    canvas: HtmlCanvasElement,
-    ctx: CanvasRenderingContext2d,
+/// Display implementation for the web platform.
+///
+/// This just caches the document to prevent having to query it every time.
+pub struct WebDisplayImpl {
+    document: web_sys::Document,
 }
 
-impl WebImpl {
-    pub fn new(handle: WebWindowHandle) -> Result<Self, SoftBufferError> {
-        let canvas: HtmlCanvasElement = web_sys::window()
+impl WebDisplayImpl {
+    pub(super) fn new() -> Result<Self, SoftBufferError> {
+        let document = web_sys::window()
             .ok_or_else(|| {
                 SoftBufferError::PlatformError(
                     Some("`window` is not present in this runtime".into()),
@@ -27,7 +29,21 @@ impl WebImpl {
                     Some("`document` is not present in this runtime".into()),
                     None,
                 )
-            })?
+            })?;
+
+        Ok(Self { document })
+    }
+}
+
+pub struct WebImpl {
+    canvas: HtmlCanvasElement,
+    ctx: CanvasRenderingContext2d,
+}
+
+impl WebImpl {
+    pub fn new(display: &WebDisplayImpl, handle: WebWindowHandle) -> Result<Self, SoftBufferError> {
+        let canvas: HtmlCanvasElement = display
+            .document
             .query_selector(&format!("canvas[data-raw-handle=\"{}\"]", handle.id))
             // `querySelector` only throws an error if the selector is invalid.
             .unwrap()