Closes #3; Fix to FFI WASM issue

When compiling to wasm32-unknown-unknown, the FFI exports
were no longer being properly recognized since Rust 1.26.
The only way to make these FFI exports recognized consistently
was to place them in the main.rs file. I have created a macro
to make this easier on the user.

3 files changed, 63 insertions, 22 deletions

diff --git a/example/src/main.rs b/example/src/main.rs
index 78b4a29..d73618c 100644
--- a/example/src/main.rs
+++ b/example/src/main.rs
@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#[macro_use]
 extern crate gate;
 
 use gate::{App, AppContext, AppInfo, KeyCode};
@@ -20,6 +21,8 @@ use gate::renderer::{Renderer, Affine};
 mod asset_id { include!(concat!(env!("OUT_DIR"), "/asset_id.rs")); }
 use asset_id::{AssetId, SpriteId, MusicId, SoundId};
 
+gate_header!();
+
 // Note: the assets that we placed in the src_assets directory can be referenced using the
 //       SpriteId, MusicId, and SoundId enums
 
diff --git a/gate/src/core/sdl/mod.rs b/gate/src/core/sdl/mod.rs
index f85d39c..0fbc97b 100644
--- a/gate/src/core/sdl/mod.rs
+++ b/gate/src/core/sdl/mod.rs
@@ -44,6 +44,11 @@ use self::app_clock::AppClock;
 use self::event_handler::EventHandler;
 use super::mark_app_created_flag;
 
+#[macro_export]
+macro_rules! gate_header {
+    () => {};
+}
+
 pub fn run<AS: AppAssetId, AP: App<AS>>(info: AppInfo, mut app: AP) {
     mark_app_created_flag();
 
diff --git a/gate/src/core/wasm/wasm_exports.rs b/gate/src/core/wasm/wasm_exports.rs
index 7681099..9b4d9d9 100644
--- a/gate/src/core/wasm/wasm_exports.rs
+++ b/gate/src/core/wasm/wasm_exports.rs
@@ -15,39 +15,36 @@
 //! This module contains methods exported to the gate javascript code for WebAssembly.
 //! DO NOT USE DIRECTLY!
 
+#![allow(non_snake_case)]
+
 use std::os::raw::{c_int, c_char};
 
 use ::input::KeyCode;
 use ::renderer::shaders;
 use super::{app_runner_is_defined, app_runner_borrow, app_runner_borrow_mut };
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmInit() {
+pub fn gateWasmInit() {
     app_runner_borrow_mut().init();
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmOnResize(w: c_int, h: c_int) {
+pub fn gateWasmOnResize(w: c_int, h: c_int) {
     app_runner_borrow_mut().resize((w as u32, h as u32));
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmUpdateAndDraw(time_millis: f64, cursor_x: c_int, cursor_y: c_int) -> c_int {
+pub fn gateWasmUpdateAndDraw(time_millis: f64, cursor_x: c_int, cursor_y: c_int) -> c_int {
     app_runner_borrow_mut().update_cursor(cursor_x as i32, cursor_y as i32);
     let continuing = app_runner_borrow_mut().update_and_draw(time_millis / 1000.0);
     if continuing { 1 } else { 0 }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmKeyEvent(code: c_int, down: bool) -> c_int {
+pub fn gateWasmKeyEvent(code: c_int, down: bool) -> c_int {
     assert!(code >= 0 && code <= 255);
     let code = KeyCode::from_u8(code as u8).unwrap();
     let continuing = app_runner_borrow_mut().input(code, down);
     if continuing { 1 } else { 0 }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmMouseEvent(cursor_x: c_int, cursor_y: c_int, button: c_int, down: bool) -> c_int {
+pub fn gateWasmMouseEvent(cursor_x: c_int, cursor_y: c_int, button: c_int, down: bool) -> c_int {
     app_runner_borrow_mut().update_cursor(cursor_x as i32, cursor_y as i32);
     let code = match button {
         0 => Some(KeyCode::MouseLeft),
@@ -63,32 +60,68 @@ pub unsafe extern "C" fn gateWasmMouseEvent(cursor_x: c_int, cursor_y: c_int, bu
     if continuing { 1 } else { 0 }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmIsAppDefined() -> c_int {
+pub fn gateWasmIsAppDefined() -> c_int {
     if app_runner_is_defined() { 1 } else { 0 }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmMusicCount() -> c_int {
+pub fn gateWasmMusicCount() -> c_int {
     app_runner_borrow().music_count() as c_int
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmSoundCount() -> c_int {
+pub fn gateWasmSoundCount() -> c_int {
     app_runner_borrow().sound_count() as c_int
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmSpriteVertSrc() -> *const c_char {
+pub fn gateWasmSpriteVertSrc() -> *const c_char {
     shaders::VS_SPRITE_SRC
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmSpriteFragSrc() -> *const c_char {
+pub fn gateWasmSpriteFragSrc() -> *const c_char {
     shaders::FS_SPRITE_SRC
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn gateWasmOnRestart() {
+pub fn gateWasmOnRestart() {
     app_runner_borrow_mut().on_restart();
 }
+
+#[macro_export]
+macro_rules! gate_header {
+    () => {
+        pub mod gate_wasm_exports {
+            use std::os::raw::{c_int, c_char};
+            #[no_mangle] pub unsafe extern "C" fn gateWasmInit() {
+                ::gate::wasm_exports::gateWasmInit()
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmOnResize(w: c_int, h: c_int) {
+                ::gate::wasm_exports::gateWasmOnResize(w, h)
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmUpdateAndDraw(time_millis: f64, cursor_x: c_int, cursor_y: c_int) -> c_int {
+                ::gate::wasm_exports::gateWasmUpdateAndDraw(time_millis, cursor_x, cursor_y)
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmKeyEvent(code: c_int, down: bool) -> c_int {
+                ::gate::wasm_exports::gateWasmKeyEvent(code, down)
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmMouseEvent(cursor_x: c_int, cursor_y: c_int, button: c_int, down: bool) -> c_int {
+                ::gate::wasm_exports::gateWasmMouseEvent(cursor_x, cursor_y, button, down)
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmIsAppDefined() -> c_int {
+                ::gate::wasm_exports::gateWasmIsAppDefined()
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmMusicCount() -> c_int {
+                ::gate::wasm_exports::gateWasmMusicCount()
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmSoundCount() -> c_int {
+                ::gate::wasm_exports::gateWasmSoundCount()
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmSpriteVertSrc() -> *const c_char {
+                ::gate::wasm_exports::gateWasmSpriteVertSrc()
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmSpriteFragSrc() -> *const c_char {
+                ::gate::wasm_exports::gateWasmSpriteFragSrc()
+            }
+            #[no_mangle] pub unsafe extern "C" fn gateWasmOnRestart() {
+                ::gate::wasm_exports::gateWasmOnRestart()
+            }
+        }
+    };
+}