Emscripten rework (#286)

* partial implementation for emscripten

this pull request contain a partial but working implementation of emscripten backend

some implementations may be controversial.

here some implementation detail:

* cursor state:
  * on grab: emscripten request pointer lock deferred and also set a callback when pointer lock change
             the callback request pointer lock deferred.
  * on hide: `emscripten_hide_mouse` exist but not `emscripten_show_mouse`
             a pull request has been open on october 2016 but never been merged
             so I copied the javascript function and put it in emscripten_asm_const function

* fullscreen: if fullscreen is requested then it request fullscreen deferred and set a callback on fullscreen change
              the callback request fullscreen deferred

* run forever: this method use emscripten main loop to run an infinite loop

* keyboard callback doesn't consume the event. I think it is more apopriate as in desktop environment it is the same, is it ?

* emscripten dir is added in example and contains html pages

Some things that are not implemented:

* lots of events

* min and max dimension can be implemented with a callback that listen to size change and resize if dimension out of bound

* title may be implemented using javascript to change document.title

* Use std::os::raw in the emscripten bindings

* Fix emscripten code

* Update code

* Add CI

* Remove the emscripten-specific examples

* Add some information to the README

.circleci/config.yml

@@ -2,17 +2,45 @@ version: 2
 
 jobs:
 
-  test:
-    working_directory: ~/tgst
+  android-test:
+    working_directory: ~/winit
     docker:
       - image: tomaka/cargo-apk
     steps:
       - checkout
       - restore_cache:
-          key: test-cache-{{ checksum "Cargo.toml" }}
+          key: android-test-cache-{{ checksum "Cargo.toml" }}
       - run: cargo apk build --example window
       - save_cache:
-          key: test-cache-{{ checksum "Cargo.toml" }}
+          key: android-test-cache-{{ checksum "Cargo.toml" }}
+          paths:
+            - target
+
+  asmjs-test:
+    working_directory: ~/winit
+    docker:
+      - image: tomaka/rustc-emscripten
+    steps:
+      - checkout
+      - restore_cache:
+          key: asmjs-test-cache-{{ checksum "Cargo.toml" }}
+      - run: cargo build --example window --target asmjs-unknown-emscripten
+      - save_cache:
+          key: asmjs-test-cache-{{ checksum "Cargo.toml" }}
+          paths:
+            - target
+
+  wasm-test:
+    working_directory: ~/winit
+    docker:
+      - image: tomaka/rustc-emscripten
+    steps:
+      - checkout
+      - restore_cache:
+          key: wasm-test-cache-{{ checksum "Cargo.toml" }}
+      - run: cargo build --example window --target wasm32-unknown-emscripten
+      - save_cache:
+          key: wasm-test-cache-{{ checksum "Cargo.toml" }}
           paths:
             - target
   
@@ -20,4 +48,6 @@ workflows:
   version: 2
   build-test-and-deploy:
     jobs:
-      - test
+      - android-test
+      - asmjs-test
+      - wasm-test

README.md

@@ -41,3 +41,15 @@ fn main() {
     });
 }
 ```
+
+### Platform-specific usage
+
+#### Emscripten and WebAssembly
+
+Building a binary will yield a `.js` file. In order to use it in an HTML file, you need to:
+
+- Put a `<canvas id="my_id"></canvas>` element somewhere. A canvas corresponds to a winit "window".
+- Write a Javascript code that creates a global variable named `Module`. Set `Module.canvas` to
+  the ID of the `<canvas>` element (in the example this would be `"my_id"`). More information
+  [here](https://kripken.github.io/emscripten-site/docs/api_reference/module.html).
+- Make sure that you insert the `.js` file generated by Rust after the `Module` variable is created.

src/platform/emscripten/ffi.rs

@@ -0,0 +1,189 @@
+#![allow(dead_code)]
+#![allow(non_snake_case)]
+#![allow(non_camel_case_types)]
+
+use std::mem;
+use std::os::raw::{c_int, c_char, c_void, c_ulong, c_double};
+
+pub type EM_BOOL = c_int;
+pub type EM_UTF8 = c_char;
+pub type EMSCRIPTEN_RESULT = c_int;
+
+pub const EM_TRUE: EM_BOOL = 1;
+pub const EM_FALSE: EM_BOOL = 0;
+
+// values for EMSCRIPTEN_RESULT
+pub const EMSCRIPTEN_RESULT_SUCCESS: c_int = 0;
+pub const EMSCRIPTEN_RESULT_DEFERRED: c_int = 1;
+pub const EMSCRIPTEN_RESULT_NOT_SUPPORTED: c_int = -1;
+pub const EMSCRIPTEN_RESULT_FAILED_NOT_DEFERRED: c_int = -2;
+pub const EMSCRIPTEN_RESULT_INVALID_TARGET: c_int = -3;
+pub const EMSCRIPTEN_RESULT_UNKNOWN_TARGET: c_int = -4;
+pub const EMSCRIPTEN_RESULT_INVALID_PARAM: c_int = -5;
+pub const EMSCRIPTEN_RESULT_FAILED: c_int = -6;
+pub const EMSCRIPTEN_RESULT_NO_DATA: c_int = -7;
+
+// values for EMSCRIPTEN EVENT
+pub const EMSCRIPTEN_EVENT_KEYPRESS: c_int = 1;
+pub const EMSCRIPTEN_EVENT_KEYDOWN: c_int = 2;
+pub const EMSCRIPTEN_EVENT_KEYUP: c_int = 3;
+pub const EMSCRIPTEN_EVENT_CLICK: c_int = 4;
+pub const EMSCRIPTEN_EVENT_MOUSEDOWN: c_int = 5;
+pub const EMSCRIPTEN_EVENT_MOUSEUP: c_int = 6;
+pub const EMSCRIPTEN_EVENT_DBLCLICK: c_int = 7;
+pub const EMSCRIPTEN_EVENT_MOUSEMOVE: c_int = 8;
+pub const EMSCRIPTEN_EVENT_WHEEL: c_int = 9;
+pub const EMSCRIPTEN_EVENT_RESIZE: c_int = 10;
+pub const EMSCRIPTEN_EVENT_SCROLL: c_int = 11;
+pub const EMSCRIPTEN_EVENT_BLUR: c_int = 12;
+pub const EMSCRIPTEN_EVENT_FOCUS: c_int = 13;
+pub const EMSCRIPTEN_EVENT_FOCUSIN: c_int = 14;
+pub const EMSCRIPTEN_EVENT_FOCUSOUT: c_int = 15;
+pub const EMSCRIPTEN_EVENT_DEVICEORIENTATION: c_int = 16;
+pub const EMSCRIPTEN_EVENT_DEVICEMOTION: c_int = 17;
+pub const EMSCRIPTEN_EVENT_ORIENTATIONCHANGE: c_int = 18;
+pub const EMSCRIPTEN_EVENT_FULLSCREENCHANGE: c_int = 19;
+pub const EMSCRIPTEN_EVENT_POINTERLOCKCHANGE: c_int = 20;
+pub const EMSCRIPTEN_EVENT_VISIBILITYCHANGE: c_int = 21;
+pub const EMSCRIPTEN_EVENT_TOUCHSTART: c_int = 22;
+pub const EMSCRIPTEN_EVENT_TOUCHEND: c_int = 23;
+pub const EMSCRIPTEN_EVENT_TOUCHMOVE: c_int = 24;
+pub const EMSCRIPTEN_EVENT_TOUCHCANCEL: c_int = 25;
+pub const EMSCRIPTEN_EVENT_GAMEPADCONNECTED: c_int = 26;
+pub const EMSCRIPTEN_EVENT_GAMEPADDISCONNECTED: c_int = 27;
+pub const EMSCRIPTEN_EVENT_BEFOREUNLOAD: c_int = 28;
+pub const EMSCRIPTEN_EVENT_BATTERYCHARGINGCHANGE: c_int = 29;
+pub const EMSCRIPTEN_EVENT_BATTERYLEVELCHANGE: c_int = 30;
+pub const EMSCRIPTEN_EVENT_WEBGLCONTEXTLOST: c_int = 31;
+pub const EMSCRIPTEN_EVENT_WEBGLCONTEXTRESTORED: c_int = 32;
+pub const EMSCRIPTEN_EVENT_MOUSEENTER: c_int = 33;
+pub const EMSCRIPTEN_EVENT_MOUSELEAVE: c_int = 34;
+pub const EMSCRIPTEN_EVENT_MOUSEOVER: c_int = 35;
+pub const EMSCRIPTEN_EVENT_MOUSEOUT: c_int = 36;
+pub const EMSCRIPTEN_EVENT_CANVASRESIZED: c_int = 37;
+pub const EMSCRIPTEN_EVENT_POINTERLOCKERROR: c_int = 38;
+
+pub const EM_HTML5_SHORT_STRING_LEN_BYTES: usize = 32;
+
+pub type em_callback_func = Option<unsafe extern "C" fn()>;
+
+pub type em_key_callback_func = Option<unsafe extern "C" fn(
+    eventType: c_int,
+    keyEvent: *const EmscriptenKeyboardEvent,
+    userData: *mut c_void) -> EM_BOOL>;
+
+pub type em_pointerlockchange_callback_func = Option<unsafe extern "C" fn(
+    eventType: c_int,
+    pointerlockChangeEvent: *const EmscriptenPointerlockChangeEvent,
+    userData: *mut c_void) -> EM_BOOL>;
+
+pub type em_fullscreenchange_callback_func = Option<unsafe extern "C" fn(
+    eventType: c_int,
+    fullscreenChangeEvent: *const EmscriptenFullscreenChangeEvent,
+    userData: *mut c_void) -> EM_BOOL>;
+
+#[repr(C)]
+pub struct EmscriptenFullscreenChangeEvent {
+    pub isFullscreen: c_int,
+    pub fullscreenEnabled: c_int,
+    pub nodeName: [c_char; 128usize],
+    pub id: [c_char; 128usize],
+    pub elementWidth: c_int,
+    pub elementHeight: c_int,
+    pub screenWidth: c_int,
+    pub screenHeight: c_int,
+}
+#[test]
+fn bindgen_test_layout_EmscriptenFullscreenChangeEvent() {
+    assert_eq!(mem::size_of::<EmscriptenFullscreenChangeEvent>(), 280usize);
+    assert_eq!(mem::align_of::<EmscriptenFullscreenChangeEvent>(), 4usize);
+}
+
+#[repr(C)]
+#[derive(Debug, Copy)]
+pub struct EmscriptenKeyboardEvent {
+    pub key: [c_char; 32usize],
+    pub code: [c_char; 32usize],
+    pub location: c_ulong,
+    pub ctrlKey: c_int,
+    pub shiftKey: c_int,
+    pub altKey: c_int,
+    pub metaKey: c_int,
+    pub repeat: c_int,
+    pub locale: [c_char; 32usize],
+    pub charValue: [c_char; 32usize],
+    pub charCode: c_ulong,
+    pub keyCode: c_ulong,
+    pub which: c_ulong,
+}
+#[test]
+fn bindgen_test_layout_EmscriptenKeyboardEvent() {
+    assert_eq!(mem::size_of::<EmscriptenKeyboardEvent>(), 184usize);
+    assert_eq!(mem::align_of::<EmscriptenKeyboardEvent>(), 8usize);
+}
+impl Clone for EmscriptenKeyboardEvent {
+    fn clone(&self) -> Self { *self }
+}
+
+#[repr(C)]
+pub struct EmscriptenPointerlockChangeEvent {
+    pub isActive: c_int,
+    pub nodeName: [c_char; 128usize],
+    pub id: [c_char; 128usize],
+}
+#[test]
+fn bindgen_test_layout_EmscriptenPointerlockChangeEvent() {
+    assert_eq!(mem::size_of::<EmscriptenPointerlockChangeEvent>(), 260usize);
+    assert_eq!(mem::align_of::<EmscriptenPointerlockChangeEvent>(), 4usize);
+}
+
+extern "C" {
+    pub fn emscripten_set_element_css_size(
+        target: *const c_char, width: c_double,
+        height: c_double) -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_get_element_css_size(
+        target: *const c_char, width: *mut c_double,
+        height: *mut c_double) -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_request_pointerlock(
+        target: *const c_char, deferUntilInEventHandler: EM_BOOL)
+        -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_exit_pointerlock() -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_request_fullscreen(
+        target: *const c_char, deferUntilInEventHandler: EM_BOOL)
+        -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_exit_fullscreen() -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_set_keydown_callback(
+        target: *const c_char, userData: *mut c_void,
+        useCapture: EM_BOOL, callback: em_key_callback_func)
+        -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_set_keyup_callback(
+        target: *const c_char, userData: *mut c_void,
+        useCapture: EM_BOOL, callback: em_key_callback_func)
+        -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_hide_mouse();
+
+    pub fn emscripten_get_device_pixel_ratio() -> f64;
+
+    pub fn emscripten_set_pointerlockchange_callback(
+        target: *const c_char, userData: *mut c_void, useCapture: EM_BOOL,
+        callback: em_pointerlockchange_callback_func) -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_set_fullscreenchange_callback(
+        target: *const c_char, userData: *mut c_void, useCapture: EM_BOOL,
+        callback: em_fullscreenchange_callback_func) -> EMSCRIPTEN_RESULT;
+
+    pub fn emscripten_asm_const(code: *const c_char);
+
+    pub fn emscripten_set_main_loop(
+        func: em_callback_func, fps: c_int, simulate_infinite_loop: EM_BOOL);
+
+    pub fn emscripten_cancel_main_loop();
+}

src/platform/emscripten/mod.rs

@@ -0,0 +1,469 @@
+#![cfg(target_os = "emscripten")]
+
+mod ffi;
+
+use std::mem;
+use std::os::raw::{c_char, c_void, c_double, c_ulong, c_int};
+use std::ptr;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Mutex, Arc, Weak};
+use std::cell::RefCell;
+use std::collections::VecDeque;
+
+const DOCUMENT_NAME: &'static str = "#document\0";
+
+#[derive(Clone, Default)]
+pub struct PlatformSpecificWindowBuilderAttributes;
+
+unsafe impl Send for PlatformSpecificWindowBuilderAttributes {}
+unsafe impl Sync for PlatformSpecificWindowBuilderAttributes {}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct DeviceId;
+
+#[derive(Clone, Default)]
+pub struct PlatformSpecificHeadlessBuilderAttributes;
+
+#[derive(Clone)]
+pub struct MonitorId;
+
+impl MonitorId {
+    #[inline]
+    pub fn get_name(&self) -> Option<String> {
+        Some("Canvas".to_owned())
+    }
+
+    #[inline]
+    pub fn get_position(&self) -> (u32, u32) {
+        unimplemented!()
+    }
+
+    #[inline]
+    pub fn get_dimensions(&self) -> (u32, u32) {
+        (0, 0)
+    }
+}
+
+// Used to assign a callback to emscripten main loop
+thread_local!(static MAIN_LOOP_CALLBACK: RefCell<*mut c_void> = RefCell::new(ptr::null_mut()));
+
+// Used to assign a callback to emscripten main loop
+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 { ffi::emscripten_set_main_loop(Some(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)();
+        });
+    }
+}
+
+pub struct EventsLoopProxy;
+
+impl EventsLoopProxy {
+    pub fn wakeup(&self) -> Result<(), ::EventsLoopClosed> {
+        unimplemented!()
+    }
+}
+
+pub struct EventsLoop {
+    window: Mutex<Option<Arc<Window2>>>,
+    interrupted: AtomicBool,
+}
+
+impl EventsLoop {
+    pub fn new() -> EventsLoop {
+        EventsLoop {
+            window: Mutex::new(None),
+            interrupted: AtomicBool::new(false),
+        }
+    }
+
+    pub fn interrupt(&self) {
+        self.interrupted.store(true, Ordering::Relaxed);
+    }
+
+    pub fn create_proxy(&self) -> EventsLoopProxy {
+        unimplemented!()
+    }
+
+    #[inline]
+    pub fn get_available_monitors(&self) -> VecDeque<MonitorId> {
+        let mut list = VecDeque::new();
+        list.push_back(MonitorId);
+        list
+    }
+
+    #[inline]
+    pub fn get_primary_monitor(&self) -> MonitorId {
+        MonitorId
+    }
+
+    pub fn poll_events<F>(&self, mut callback: F)
+        where F: FnMut(::Event)
+    {
+        let ref mut window = *self.window.lock().unwrap();
+        if let &mut Some(ref mut window) = window {
+            while let Some(event) = window.events.borrow_mut().pop_front() {
+                callback(event)
+            }
+        }
+    }
+
+    pub fn run_forever<F>(&self, mut callback: F)
+        where F: FnMut(::Event) -> ::ControlFlow
+    {
+        self.interrupted.store(false, Ordering::Relaxed);
+
+        // TODO: handle control flow
+
+        set_main_loop_callback(|| {
+            self.poll_events(|e| { callback(e); });
+            ::std::thread::sleep(::std::time::Duration::from_millis(5));
+            if self.interrupted.load(Ordering::Relaxed) {
+                unsafe { ffi::emscripten_cancel_main_loop(); }
+            }
+        });
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct WindowId(usize);
+
+pub struct Window2 {
+    cursor_state: Mutex<::CursorState>,
+    is_fullscreen: bool,
+    events: Box<RefCell<VecDeque<::Event>>>,
+}
+
+pub struct Window {
+    window: Arc<Window2>,
+}
+
+fn show_mouse() {
+    // Hide mouse hasn't show mouse equivalent.
+    // There is a pull request on emscripten that hasn't been merged #4616
+    // that contains:
+    //
+    // var styleSheet = document.styleSheets[0];
+    // var rules = styleSheet.cssRules;
+    // for (var i = 0; i < rules.length; i++) {
+    //   if (rules[i].cssText.substr(0, 6) == 'canvas') {
+    //     styleSheet.deleteRule(i);
+    //     i--;
+    //   }
+    // }
+    // styleSheet.insertRule('canvas.emscripten { border: none; cursor: auto; }', 0);
+    unsafe {
+            ffi::emscripten_asm_const(b"var styleSheet = document.styleSheets[0]; var rules = styleSheet.cssRules; for (var i = 0; i < rules.length; i++) { if (rules[i].cssText.substr(0, 6) == 'canvas') { styleSheet.deleteRule(i); i--; } } styleSheet.insertRule('canvas.emscripten { border: none; cursor: auto; }', 0);\0".as_ptr() as *const c_char);
+    }
+}
+
+extern "C" fn keyboard_callback(
+    event_type: c_int,
+    event: *const ffi::EmscriptenKeyboardEvent,
+    event_queue: *mut c_void) -> ffi::EM_BOOL
+{
+    unsafe {
+        let queue: &RefCell<VecDeque<::Event>> = mem::transmute(event_queue);
+        match event_type {
+            ffi::EMSCRIPTEN_EVENT_KEYDOWN => {
+                queue.borrow_mut().push_back(::Event::WindowEvent {
+                    window_id: ::WindowId(WindowId(0)),
+                    event: ::WindowEvent::KeyboardInput {
+                        device_id: ::DeviceId(DeviceId),
+                        input: ::KeyboardInput {
+                            scancode: key_translate((*event).key) as u32,
+                            state: ::ElementState::Pressed,
+                            virtual_keycode: key_translate_virt((*event).key, (*event).location),
+                            modifiers: ::ModifiersState::default()        // TODO:
+                        },   
+                    },
+                });
+            },
+            ffi::EMSCRIPTEN_EVENT_KEYUP => {
+                queue.borrow_mut().push_back(::Event::WindowEvent {
+                    window_id: ::WindowId(WindowId(0)),
+                    event: ::WindowEvent::KeyboardInput {
+                        device_id: ::DeviceId(DeviceId),
+                        input: ::KeyboardInput {
+                            scancode: key_translate((*event).key) as u32,
+                            state: ::ElementState::Released,
+                            virtual_keycode: key_translate_virt((*event).key, (*event).location),
+                            modifiers: ::ModifiersState::default()        // TODO:
+                        },
+                    },
+                });
+            },
+            _ => {
+            }
+        }
+    }
+    ffi::EM_FALSE
+}
+
+// In case of fullscreen window this method will request fullscreen on change
+#[allow(non_snake_case)]
+unsafe extern "C" fn fullscreen_callback(
+    _eventType: c_int,
+    _fullscreenChangeEvent: *const ffi::EmscriptenFullscreenChangeEvent,
+    _userData: *mut c_void) -> ffi::EM_BOOL
+{
+    ffi::emscripten_request_fullscreen(ptr::null(), ffi::EM_TRUE);
+    ffi::EM_FALSE
+}
+
+// In case of pointer grabbed this method will request pointer lock on change
+#[allow(non_snake_case)]
+unsafe extern "C" fn pointerlockchange_callback(
+    _eventType: c_int,
+    _pointerlockChangeEvent: *const ffi::EmscriptenPointerlockChangeEvent,
+    _userData: *mut c_void) -> ffi::EM_BOOL
+{
+    ffi::emscripten_request_pointerlock(ptr::null(), ffi::EM_TRUE);
+    ffi::EM_FALSE
+}
+
+fn em_try(res: ffi::EMSCRIPTEN_RESULT) -> Result<(), String> {
+    match res {
+        ffi::EMSCRIPTEN_RESULT_SUCCESS | ffi::EMSCRIPTEN_RESULT_DEFERRED => Ok(()),
+        r @ _ => Err(error_to_str(r).to_string()),
+    }
+}
+
+impl Window {
+    pub fn new(events_loop: &EventsLoop, attribs: &::WindowAttributes,
+               _pl_attribs: &PlatformSpecificWindowBuilderAttributes)
+        -> Result<Window, ::CreationError>
+    {
+        if events_loop.window.lock().unwrap().is_some() {
+            return Err(::CreationError::OsError("Cannot create another window".to_owned()));
+        }
+
+        let w = Window2 {
+            cursor_state: Mutex::new(::CursorState::Normal),
+            events: Box::new(RefCell::new(VecDeque::new())),
+            is_fullscreen: attribs.fullscreen.is_some(),
+        };
+
+        let window = Window {
+            window: Arc::new(w),
+        };
+
+
+        // TODO: set up more event callbacks
+        unsafe {
+            em_try(ffi::emscripten_set_keydown_callback(DOCUMENT_NAME.as_ptr() as *const c_char, mem::transmute(&*window.window.events), ffi::EM_FALSE, Some(keyboard_callback)))
+                .map_err(|e| ::CreationError::OsError(format!("emscripten error: {}", e)))?;
+            em_try(ffi::emscripten_set_keyup_callback(DOCUMENT_NAME.as_ptr() as *const c_char, mem::transmute(&*window.window.events), ffi::EM_FALSE, Some(keyboard_callback)))
+                .map_err(|e| ::CreationError::OsError(format!("emscripten error: {}", e)))?;
+        }
+
+        if attribs.fullscreen.is_some() {
+            unsafe {
+                em_try(ffi::emscripten_request_fullscreen(ptr::null(), ffi::EM_TRUE))
+                    .map_err(|e| ::CreationError::OsError(e))?;
+                em_try(ffi::emscripten_set_fullscreenchange_callback(ptr::null(), 0 as *mut c_void, ffi::EM_FALSE, Some(fullscreen_callback)))
+                    .map_err(|e| ::CreationError::OsError(e))?;
+            }
+        } else if let Some((w, h)) = attribs.dimensions {
+            window.set_inner_size(w, h);
+        }
+
+        *events_loop.window.lock().unwrap() = Some(window.window.clone());
+        Ok(window)
+    }
+
+    #[inline]
+    pub fn id(&self) -> WindowId {
+        WindowId(0)
+    }
+
+    #[inline]
+    pub fn set_title(&self, _title: &str) {
+    }
+
+    #[inline]
+    pub fn get_position(&self) -> Option<(i32, i32)> {
+        Some((0, 0))
+    }
+
+    #[inline]
+    pub fn set_position(&self, _: i32, _: i32) {
+    }
+
+    pub fn get_inner_size(&self) -> Option<(u32, u32)> {
+        unsafe {
+            use std::{mem, ptr};
+            let mut width = mem::uninitialized();
+            let mut height = mem::uninitialized();
+
+            if ffi::emscripten_get_element_css_size(ptr::null(), &mut width, &mut height)
+                != ffi::EMSCRIPTEN_RESULT_SUCCESS
+            {
+                None
+            } else {
+                Some((width as u32, height as u32))
+            }
+        }
+    }
+
+    #[inline]
+    pub fn get_outer_size(&self) -> Option<(u32, u32)> {
+        self.get_inner_size()
+    }
+
+    #[inline]
+    pub fn set_inner_size(&self, width: u32, height: u32) {
+        unsafe {
+            use std::ptr;
+            ffi::emscripten_set_element_css_size(ptr::null(), width as c_double, height
+                as c_double);
+        }
+    }
+
+    #[inline]
+    pub fn show(&self) {}
+    #[inline]
+    pub fn hide(&self) {}
+
+    #[inline]
+    pub fn platform_display(&self) -> *mut ::libc::c_void {
+        unimplemented!()
+    }
+
+    #[inline]
+    pub fn platform_window(&self) -> *mut ::libc::c_void {
+        unimplemented!()
+    }
+
+    #[inline]
+    pub fn set_cursor(&self, _cursor: ::MouseCursor) {}
+
+    #[inline]
+    pub fn set_cursor_state(&self, state: ::CursorState) -> Result<(), String> {
+        unsafe {
+            use ::CursorState::*;
+
+            let mut old_state = self.window.cursor_state.lock().unwrap();
+            if state == *old_state {
+                return Ok(());
+            }
+
+            // Set or unset grab callback
+            match state {
+                Hide | Normal => em_try(ffi::emscripten_set_pointerlockchange_callback(ptr::null(), 0 as *mut c_void, ffi::EM_FALSE, None))?,
+                Grab => em_try(ffi::emscripten_set_pointerlockchange_callback(ptr::null(), 0 as *mut c_void, ffi::EM_FALSE, Some(pointerlockchange_callback)))?,
+            }
+
+            // Go back to normal cursor state
+            match *old_state {
+                Hide => show_mouse(),
+                Grab => em_try(ffi::emscripten_exit_pointerlock())?,
+                Normal => (),
+            }
+
+            // Set cursor from normal cursor state
+            match state {
+                Hide => ffi::emscripten_hide_mouse(),
+                Grab => em_try(ffi::emscripten_request_pointerlock(ptr::null(), ffi::EM_TRUE))?,
+                Normal => (),
+            }
+
+            // Update
+            *old_state = state;
+
+            Ok(())
+        }
+    }
+
+    #[inline]
+    pub fn hidpi_factor(&self) -> f32 {
+        unsafe { ffi::emscripten_get_device_pixel_ratio() as f32 }
+    }
+
+    #[inline]
+    pub fn set_cursor_position(&self, _x: i32, _y: i32) -> Result<(), ()> {
+        Err(())
+    }
+
+    #[inline]
+    pub fn set_maximized(&self, _maximized: bool) {
+        // iOS has single screen maximized apps so nothing to do
+    }
+
+    #[inline]
+    pub fn set_fullscreen(&self, _monitor: Option<::MonitorId>) {
+        // iOS has single screen maximized apps so nothing to do
+    }
+
+    #[inline]
+    pub fn get_current_monitor(&self) -> ::MonitorId {
+        ::MonitorId{inner: MonitorId}
+    }
+}
+
+impl Drop for Window {
+    fn drop(&mut self) {
+        // Delete window from events_loop
+        // TODO: ?
+        /*if let Some(ev) = self.events_loop.upgrade() {
+            let _ = ev.window.lock().unwrap().take().unwrap();
+        }*/
+
+        unsafe {
+            // Return back to normal cursor state
+            let _ = self.set_cursor_state(::CursorState::Normal);
+
+            // Exit fullscreen if on
+            if self.window.is_fullscreen {
+                ffi::emscripten_set_fullscreenchange_callback(ptr::null(), 0 as *mut c_void, ffi::EM_FALSE, None);
+                ffi::emscripten_exit_fullscreen();
+            }
+
+            // Delete callbacks
+            ffi::emscripten_set_keydown_callback(DOCUMENT_NAME.as_ptr() as *const c_char, 0 as *mut c_void, ffi::EM_FALSE,None);
+            ffi::emscripten_set_keyup_callback(DOCUMENT_NAME.as_ptr() as *const c_char, 0 as *mut c_void, ffi::EM_FALSE,None);
+        }
+    }
+}
+
+fn error_to_str(code: ffi::EMSCRIPTEN_RESULT) -> &'static str {
+    match code {
+        ffi::EMSCRIPTEN_RESULT_SUCCESS | ffi::EMSCRIPTEN_RESULT_DEFERRED
+            => "Internal error in the library (success detected as failure)",
+
+        ffi::EMSCRIPTEN_RESULT_NOT_SUPPORTED => "Not supported",
+        ffi::EMSCRIPTEN_RESULT_FAILED_NOT_DEFERRED => "Failed not deferred",
+        ffi::EMSCRIPTEN_RESULT_INVALID_TARGET => "Invalid target",
+        ffi::EMSCRIPTEN_RESULT_UNKNOWN_TARGET => "Unknown target",
+        ffi::EMSCRIPTEN_RESULT_INVALID_PARAM => "Invalid parameter",
+        ffi::EMSCRIPTEN_RESULT_FAILED => "Failed",
+        ffi::EMSCRIPTEN_RESULT_NO_DATA => "No data",
+
+        _ => "Undocumented error"
+    }
+}
+
+fn key_translate(input: [ffi::EM_UTF8; ffi::EM_HTML5_SHORT_STRING_LEN_BYTES]) -> u8 {
+    use std::str;
+    let slice = &input[0..input.iter().take_while(|x| **x != 0).count()];
+    let key = unsafe { str::from_utf8(mem::transmute::<&[i8], &[u8]>(slice)).unwrap() };
+    if key.chars().count() == 1 {
+        key.as_bytes()[0]
+    } else {
+        0
+    }
+}
+
+fn key_translate_virt(_input: [ffi::EM_UTF8; ffi::EM_HTML5_SHORT_STRING_LEN_BYTES],
+                      _location: c_ulong) -> Option<::VirtualKeyCode>
+{
+    // TODO
+    None
+}

src/platform/mod.rs

@@ -15,8 +15,11 @@ mod platform;
 #[cfg(target_os = "ios")]
 #[path="ios/mod.rs"]
 mod platform;
+#[cfg(target_os = "emscripten")]
+#[path="emscripten/mod.rs"]
+mod platform;
 
 #[cfg(all(not(target_os = "ios"), not(target_os = "windows"), not(target_os = "linux"),
   not(target_os = "macos"), not(target_os = "android"), not(target_os = "dragonfly"),
-  not(target_os = "freebsd"), not(target_os = "openbsd")))]
+  not(target_os = "freebsd"), not(target_os = "openbsd"), not(target_os = "emscripten")))]
 use this_platform_is_not_supported;