From 695fe7d1558965c07f80b0819eafc987f25331ce Mon Sep 17 00:00:00 2001
From: Par Wenaker <par.wenaker@callistaenterprise.se>
Date: Sat, 19 Feb 2022 17:33:30 +0100
Subject: [PATCH] Add Emscripten build

---
 .gitignore     |  5 ++++-
 CMakeLists.txt | 20 +++++++++++++++-----
 README.md      | 21 +++++++++++++++++++++
 src/Main.cpp   | 22 +++++++++++++++++-----
 4 files changed, 57 insertions(+), 11 deletions(-)

diff --git a/.gitignore b/.gitignore
index e2b458e..134a64c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,4 +6,7 @@ lib/*
 bin/*
 
 # Ignore Mac specific files
-.DS_Store
\ No newline at end of file
+.DS_Store
+
+# Ignore VSCODE settings
+.vscode
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3d987ba..c8b3e32 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -4,10 +4,18 @@ project(smb)
 
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/")
 
-find_package(SDL2_mixer REQUIRED)
-find_package(SDL2 REQUIRED)
-find_package(SDL2_image REQUIRED)
-find_package(SDL2_ttf REQUIRED)
+if ( ${CMAKE_SYSTEM_NAME} MATCHES "Emscripten" )
+   set(USE_FLAGS "-s USE_SDL=2 -s USE_SDL_IMAGE=2 -s USE_SDL_TTF=2 -s USE_SDL_MIXER=2")
+   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${USE_FLAGS}")
+   set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${USE_FLAGS}")
+   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${USE_FLAGS} -s WASM=1 -s ALLOW_MEMORY_GROWTH=1 --preload-file ../assets@/assets --use-preload-plugins")
+   set(CMAKE_EXECUTABLE_SUFFIX .html)
+else ()
+   find_package(SDL2_mixer REQUIRED)
+   find_package(SDL2 REQUIRED)
+   find_package(SDL2_image REQUIRED)
+   find_package(SDL2_ttf REQUIRED)
+endif ()
 
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/bin")
 
@@ -26,5 +34,7 @@ set_property(TARGET smb PROPERTY CXX_STANDARD 17)
 set_target_properties(smb PROPERTIES OUTPUT_NAME smb-${CMAKE_BUILD_TYPE})
 target_include_directories(smb PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include)
 target_include_directories(smb PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/vendor)
-target_link_libraries(smb PRIVATE ${SDL2_MIXER_LIBRARY} ${SDL2} ${SDL2_IMAGE} ${SDL2_TTF})
+if ( NOT ${CMAKE_SYSTEM_NAME} MATCHES "Emscripten" )
+   target_link_libraries(smb PRIVATE ${SDL2_MIXER_LIBRARY} ${SDL2} ${SDL2_IMAGE} ${SDL2_TTF})
+endif ()
 
diff --git a/README.md b/README.md
index a6fbdb2..e48b1d1 100644
--- a/README.md
+++ b/README.md
@@ -41,6 +41,27 @@ $ cd ../bin/
 $ ./smb-
 ```
 
+## Webassembly
+
+Either install [emsdk](https://emscripten.org/docs/getting_started/downloads.html) and run
+```
+$ mkdir build
+$ cd build
+$ emcmake cmake ..
+$ make
+```
+or build with [Docker](https://www.docker.com/)
+```
+$ docker run --rm -v $(pwd):/src -u $(id -u):$(id -g) emscripten/emsdk emcmake cmake -S . -B build
+$ docker run --rm -v $(pwd):/src -u $(id -u):$(id -g) emscripten/emsdk cmake --build build
+```
+Start a webserver in the bin folder
+```
+$ cd bin
+$ python -m SimpleHTTPServer 8000
+$ open http://localhost:8000/smb-.html
+```
+
 ## Screenshots
 
 ![Game screenshot](https://github.com/feresr/super-mario-bros/blob/master/readme/game.png)
diff --git a/src/Main.cpp b/src/Main.cpp
index ad7f4eb..86a6476 100644
--- a/src/Main.cpp
+++ b/src/Main.cpp
@@ -1,22 +1,34 @@
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
 #include "Game.h"
 
+void runLoop(void* arg) {
+    Game *game = (Game*)arg;
+    game->handleEvents();
+    game->update();
+}
+
 int main() {
     uint32_t frameStart, frameTime;
 
     Game* game = new Game();
     game->init("Super Mario Bros",
-               SNES_RESOLUTION_WIDTH * ZOOM,
-               SNES_RESOLUTION_HEIGHT * ZOOM,
-               false);
+            SNES_RESOLUTION_WIDTH * ZOOM,
+            SNES_RESOLUTION_HEIGHT * ZOOM,
+            false);
 
+#ifdef __EMSCRIPTEN__
+    emscripten_set_main_loop_arg(runLoop, game, 0, 1);
+#else
     while (game->running()) {
         frameStart = SDL_GetTicks();
-        game->handleEvents();
-        game->update();
+        runLoop(game);
         frameTime = SDL_GetTicks() - frameStart;
         if (frameTime < FRAME_DURATION) SDL_Delay(FRAME_DURATION - frameTime);
     }
 
+#endif
     game->clean();
     delete game;
     return EXIT_SUCCESS;