feat: setup emscripten module for api layer

src/emscripten.rs

@@ -0,0 +1,31 @@
+#[allow(dead_code)]
+#[cfg(target_os = "emscripten")]
+pub mod emscripten {
+    use std::os::raw::c_uint;
+
+    extern "C" {
+        pub fn emscripten_get_now() -> f64;
+        pub fn emscripten_sleep(ms: c_uint);
+        pub fn emscripten_get_element_css_size(target: *const u8, width: *mut f64, height: *mut f64) -> i32;
+    }
+
+    // milliseconds since start of program
+    pub fn now() -> f64 {
+        unsafe { emscripten_get_now() }
+    }
+
+    pub fn sleep(ms: u32) {
+        unsafe {
+            emscripten_sleep(ms);
+        }
+    }
+
+    pub fn get_canvas_size() -> (u32, u32) {
+        let mut width = 0.0;
+        let mut height = 0.0;
+        unsafe {
+            emscripten_get_element_css_size("canvas\0".as_ptr(), &mut width, &mut height);
+        }
+        (width as u32, height as u32)
+    }
+}

src/main.rs

@@ -59,6 +59,8 @@ mod constants;
 mod debug;
 mod direction;
 mod edible;
+#[cfg(target_os = "emscripten")]
+mod emscripten;
 mod entity;
 mod game;
 mod ghost;
@@ -68,6 +70,26 @@ mod map;
 mod modulation;
 mod pacman;
 
+#[cfg(not(target_os = "emscripten"))]
+fn sleep(value: Duration) {
+    spin_sleep::sleep(value);
+}
+
+#[cfg(target_os = "emscripten")]
+fn sleep(value: Duration) {
+    emscripten::emscripten::sleep(value.as_millis() as u32);
+}
+
+#[cfg(target_os = "emscripten")]
+fn now() -> std::time::Instant {
+    std::time::Instant::now() + std::time::Duration::from_millis(emscripten::emscripten::now() as u64)
+}
+
+#[cfg(not(target_os = "emscripten"))]
+fn now() -> std::time::Instant {
+    std::time::Instant::now()
+}
+
 /// The main entry point of the application.
 ///
 /// This function initializes SDL, the window, the game state, and then enters
@@ -179,14 +201,7 @@ pub fn main() {
         if start.elapsed() < loop_time {
             let time = loop_time.saturating_sub(start.elapsed());
             if time != Duration::ZERO {
-                #[cfg(not(target_os = "emscripten"))]
-                {
-                    spin_sleep::sleep(time);
-                }
-                #[cfg(target_os = "emscripten")]
-                {
-                    std::thread::sleep(time);
-                }
+                sleep(time);
             }
         } else {
             event!(