From 02231403df6241d08ea61600713fc1565bb22956 Mon Sep 17 00:00:00 2001
From: Tom Barrett <tom@tombarrett.xyz>
Date: Mon, 27 Jul 2020 13:31:53 +0200
Subject: emscripten stuff

---
 src/emscripten.rs | 44 ++++++++++++++++++++++++++++++++
 src/main.rs       | 76 ++++++++++++++++++++++++++++++++-----------------------
 2 files changed, 89 insertions(+), 31 deletions(-)
 create mode 100644 src/emscripten.rs

(limited to 'src')

diff --git a/src/emscripten.rs b/src/emscripten.rs
new file mode 100644
index 0000000..3b9b12c
--- /dev/null
+++ b/src/emscripten.rs
@@ -0,0 +1,44 @@
+#[cfg(target_os = "emscripten")]
+pub mod emscripten {
+    use std::cell::RefCell;
+    use std::os::raw::{c_float, c_int, c_void};
+    use std::ptr::null_mut;
+
+    #[allow(non_camel_case_types)]
+    type em_callback_func = unsafe extern "C" fn();
+
+    extern "C" {
+        pub fn emscripten_set_main_loop(
+            func: em_callback_func,
+            fps: c_int,
+            simulate_infinite_loop: c_int,
+        );
+        pub fn emscripten_cancel_main_loop();
+        pub fn emscripten_get_now() -> c_float;
+    }
+
+    thread_local!(static MAIN_LOOP_CALLBACK: RefCell<*mut c_void> = RefCell::new(null_mut()));
+
+    pub fn set_main_loop_callback<F>(callback: F)
+    where
+        F: FnMut(),
+    {
+        MAIN_LOOP_CALLBACK.with(|log| {
+            *log.borrow_mut() = &callback as *const _ as *mut c_void;
+        });
+
+        unsafe {
+            emscripten_set_main_loop(wrapper::<F>, 0, 1);
+        }
+
+        unsafe extern "C" fn wrapper<F>()
+        where
+            F: FnMut(),
+        {
+            MAIN_LOOP_CALLBACK.with(|z| {
+                let closure = *z.borrow_mut() as *mut F;
+                (*closure)();
+            });
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 51a6ed9..edf6f2e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -10,6 +10,9 @@ use sdl2::event::Event;
 use sdl2::gfx::primitives::DrawRenderer;
 use sdl2::pixels::Color;
 
+#[cfg(target_os = "emscripten")]
+pub mod emscripten;
+
 fn find_origin() -> (i16, i16) {
     let mut rng = rand::thread_rng();
     (rng.gen_range(100, 400), rng.gen_range(100, 400))
@@ -71,8 +74,8 @@ fn main() {
     let mut rng = rand::thread_rng();
     lines.shuffle(&mut rng);
 
-    let a = rng.gen_range(-5.0, 5.0);
-    let b = rng.gen_range(-5.0, 5.0);
+    let a = rng.gen_range(-7.0, 7.0);
+    let b = rng.gen_range(-7.0, 7.0);
 
     let mut pixels = Vec::new();
     for i in (1000..200000).step_by(10) {
@@ -85,36 +88,47 @@ fn main() {
         });
     }
 
-    let mut i = 0;
-    let mut run = true;
-    while run {
-        for event in events.poll_iter() {
-            if let Event::Quit { .. } = event {
-                run = false
-            };
-        }
+    let mut main_loop = || {
+        let mut i = 0;
+        let mut run = true;
+        while run {
+            for event in events.poll_iter() {
+                if let Event::Quit { .. } = event {
+                    run = false
+                };
+            }
 
-        if i < lines.len() {
-            let line = &lines[i];
-            canvas
-                .line(
-                    line.x1,
-                    line.y1,
-                    line.x2,
-                    line.y2,
-                    Color::RGB(255, 255, 255),
-                )
-                .unwrap();
-        }
-        if i < pixels.len() {
-            let pixel = &pixels[i];
-            canvas
-                .pixel(pixel.x, pixel.y, Color::RGB(255, 255, 255))
-                .unwrap();
+            if i < lines.len() {
+                let line = &lines[i];
+                canvas
+                    .line(
+                        line.x1,
+                        line.y1,
+                        line.x2,
+                        line.y2,
+                        Color::RGB(255, 255, 255),
+                    )
+                    .unwrap();
+            }
+            if i < pixels.len() {
+                let pixel = &pixels[i];
+                canvas
+                    .pixel(pixel.x, pixel.y, Color::RGB(255, 255, 255))
+                    .unwrap();
+            }
+
+            canvas.present();
+            thread::sleep(Duration::from_millis(10));
+            i += 1;
         }
+    };
 
-        canvas.present();
-        thread::sleep(Duration::from_millis(10));
-        i += 1;
-    }
+    #[cfg(target_os = "emscripten")]
+    use emscripten::emscripten;
+
+    #[cfg(target_os = "emscripten")]
+    emscripten::set_main_loop_callback(main_loop);
+
+    #[cfg(not(target_os = "emscripten"))]
+    main_loop();
 }
-- 
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