From 0063e1c3bc71e92c1ae537bc4c1962e689277d2d Mon Sep 17 00:00:00 2001
From: leo60228 <leo@60228.dev>
Date: Wed, 31 Mar 2021 15:06:26 -0400
Subject: [PATCH] Use Emscripten's main loop

On Emscripten, SDL_Delay is implemented as a busy loop. In addition,
everything happens on a single thread. This effectively means that
you have to let Emscripten manage the main loop, since if you do it
yourself the browser will just be frozen.
---
 desktop_version/src/main.cpp | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/desktop_version/src/main.cpp b/desktop_version/src/main.cpp
index a384d534..b6dd64c3 100644
--- a/desktop_version/src/main.cpp
+++ b/desktop_version/src/main.cpp
@@ -23,6 +23,11 @@
 #include "SoundSystem.h"
 #include "UtilityClass.h"
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#include <emscripten/html5.h>
+#endif
+
 scriptclass script;
 
 #if !defined(NO_CUSTOM_LEVELS)
@@ -54,8 +59,11 @@ static std::string playtestname;
 static volatile Uint32 time_ = 0;
 static volatile Uint32 timePrev = 0;
 static volatile Uint32 accumulator = 0;
+
+#ifndef __EMSCRIPTEN__
 static volatile Uint32 f_time = 0;
 static volatile Uint32 f_timePrev = 0;
+#endif
 
 enum FuncType
 {
@@ -339,6 +347,15 @@ static void inline deltaloop(void);
 
 static void cleanup(void);
 
+#ifdef __EMSCRIPTEN__
+void emscriptenloop()
+{
+    timePrev = time_;
+    time_ = SDL_GetTicks();
+    deltaloop();
+}
+#endif
+
 int main(int argc, char *argv[])
 {
     char* baseDir = NULL;
@@ -611,6 +628,9 @@ int main(int argc, char *argv[])
     gamestate_funcs = get_gamestate_funcs(game.gamestate, &num_gamestate_funcs);
     loop_assign_active_funcs();
 
+#ifdef __EMSCRIPTEN__
+    emscripten_set_main_loop(emscriptenloop, 0, 0);
+#else
     while (true)
     {
         f_time = SDL_GetTicks();
@@ -632,6 +652,8 @@ int main(int argc, char *argv[])
     }
 
     cleanup();
+#endif
+
     return 0;
 }
 
@@ -731,7 +753,9 @@ static void unfocused_run(void)
     graphics.render();
     gameScreen.FlipScreen();
     //We are minimised, so lets put a bit of a delay to save CPU
+#ifndef __EMSCRIPTEN__
     SDL_Delay(100);
+#endif
 }
 
 static void focused_begin(void)