DISTS: New Emscripten/WebAssembly dists target

This is an initial version of the emscripten build/dist target. Many things are still missing, see dists/emscripten/README.md for a detailed summary of what this provides and still misses
2025-04-02 23:01:42 +00:00 · 2021-06-02 00:59:09 +02:00 · 2021-06-02 00:59:09 +02:00 · b7a2e22b0a
commit b7a2e22b0a
parent 2f3b74e485
11 changed files with 608 additions and 1 deletions
--- a/.gitignore
+++ b/.gitignore
@ -279,3 +279,9 @@ android_project

 #Ignore snapcraft build artifacts
 .snap
+
+#Ignore emscripten build artifacts
+dists/emscripten/emsdk-*/
+dists/emscripten/libs/
+dists/emscripten/games/
+dists/emscripten/emsdk-*
--- a/backends/graphics3d/openglsdl/openglsdl-graphics3d.cpp
+++ b/backends/graphics3d/openglsdl/openglsdl-graphics3d.cpp
@ -180,7 +180,12 @@ void OpenGLSdlGraphics3dManager::setupScreen() {
 		// So check if the window needs to be recreated.

 		int currentSamples = 0;
+		#if defined(EMSCRIPTEN)
+		// SDL_GL_MULTISAMPLESAMPLES isn't available on the WebGL context (or not bridged in Emscripten?), let's just reset the windows every time
+		currentSamples = -1;
+		#else
 		SDL_GL_GetAttribute(SDL_GL_MULTISAMPLESAMPLES, &currentSamples);
+		#endif

 		// When rendering to a framebuffer, MSAA is enabled on that framebuffer, not on the screen
 		int targetSamples = shouldRenderToFramebuffer() ? 0 : _antialiasing;
--- a/63
+++ b/63
@ -561,6 +561,9 @@ get_system_exe_extension() {
 	mingw* | *os2-emx)
 		_exeext=".exe"
 		;;
+	emscripten)
+		_exeext=".html"	
+		;;
 	*)
 		_exeext=""
 		;;
@ -1720,6 +1723,12 @@ switch)
 	# Switch SDK has C++11 constructs so we must enable it
 	_use_cxx11=yes
 	;;
+wasm32-*)
+	_endian=little # the endian check below fails, but emscripten is always little endian anyway
+	_host_os=emscripten
+	_host_cpu=wasm32
+	CXX="em++"
+	;;
 wii)
 	_host_os=wii
 	_host_cpu=powerpc
@ -1806,6 +1815,12 @@ dreamcast)
 		exit 1
 	fi
 	;;
+emscripten)
+	if test -z "$EMSDK"; then
+		echo "Please set EMSDK in your environment. export EMSDK=<path to emscripten sdk>"
+		exit 1
+	fi
+	;;
 n64)
 	if test -z "$N64SDK"; then
 		echo "Please set N64SDK in your environment. export N64SDK=<path to n64 sdk>"
@ -2570,6 +2585,9 @@ case $_host_cpu in
 	amd64 | x86_64)
 		echo "x86_64"
 		;;
+	wasm32)
+		echo "wasm32"
+		;;
 	*)
 		echo "unknown ($_host_cpu)"
 		;;
@ -2893,6 +2911,25 @@ EOF
 		append_var LIBS "-lmm9"
 		append_var LIBS "-lnds9"
 		;;
+	emscripten)
+		add_line_to_config_mk 'EMSCRIPTEN = 1'
+		# mandatory emscripten flags
+		append_var LDFLAGS "-s MAX_WEBGL_VERSION=2 -s WEBGL2_BACKWARDS_COMPATIBILITY_EMULATION=1 -s ASYNCIFY -s FORCE_FILESYSTEM=1 -s ALLOW_MEMORY_GROWTH=1"
+		# enable emscripten-ports and set up paths accordingly
+		append_var LDFLAGS "-s USE_SDL=2 -s USE_SDL_MIXER=2  -s USE_OGG=1 -s USE_VORBIS=1  -s USE_LIBJPEG=1  -s USE_FREETYPE=1 -s USE_ZLIB"
+		_sdlpath="$EMSDK/upstream/emscripten/system/bin/"
+		_pngpath="$EMSDK/upstream/emscripten/cache/"
+		_freetypepath="$EMSDK/upstream/emscripten/cache/ports-builds/freetype/"
+		VORBIS_CFLAGS="-I$EMSDK/upstream/emscripten/cache//ports-builds/vorbis/include"
+		VORBIS_LIBS="-L$EMSDK/upstream/emscripten/cache//ports-builds/vorbis/lib"
+		FREETYPE2_CFLAGS="-I$_freetypepath/include"
+		_freetype_found="true"
+		if test "$_debug_build" = no; then
+			_optimization_level=-O3 -g4 
+		else
+			_optimization_level=-O2
+		fi
+	;;	
 	freebsd* | openbsd*)
 		append_var LDFLAGS "-L/usr/local/lib"
 		append_var CXXFLAGS "-I/usr/local/include"
@ -3229,6 +3266,15 @@ if test -n "$_host"; then
 			_seq_midi=no
 			_port_mk="backends/platform/dingux/dingux.mk"
 			;;
+		wasm*-emscripten)
+			_backend="sdl"
+			HOSTEXEPRE=
+			HOSTEXEEXT=.html
+			_ar="emar cru"
+			_ranlib="emranlib"
+			_opengl_mode=gles2
+			_opengl_game_es2=yes
+			;;
 		raspberrypi)
 			_libcurlpath=$RPI_ROOT/usr/bin
 			# This is needed because the official cross compiler doesn't have multiarch enabled
@ -3927,6 +3973,9 @@ case $_host_os in
 	os2-emx*)
 		_posix=yes	# FIXME: Really???
 		;;
+	emscripten)
+		_posix=yes	
+		;;
 	*)
 		# given this is a shell script, we might assume some type of posix.
 		# However, the host system might be a totally different one, so
@ -3947,7 +3996,7 @@ if test "$_posix" = yes ; then
 #include <spawn.h>
 int main(void) { return posix_spawn(0, 0, 0, 0, 0, 0); }
 EOF
-	cc_check && _has_posix_spawn=yes
+	cc_check && test "$_host_os" != "emscripten" && _has_posix_spawn=yes
 	echo $_has_posix_spawn
 	if test "$_has_posix_spawn" = yes ; then
 		append_var DEFINES "-DHAS_POSIX_SPAWN"
@ -3994,6 +4043,18 @@ _mak_plugins=
 if test "$_dynamic_modules" = yes ; then
 	echo_n "Checking whether building plugins is supported... "
 	case $_host_os in
+	emscripten)
+		_plugin_prefix="lib"
+		_plugin_suffix=".wasm"
+		append_var CXXFLAGS "-fPIC"
+		append_var LIBS ""
+_mak_plugins='
+PLUGIN_EXTRA_DEPS =
+PLUGIN_LDFLAGS  += -s SIDE_MODULE=1 -s EXPORT_ALL=1
+PRE_OBJS_FLAGS  := -s MAIN_MODULE=1 -s EXPORT_ALL=1
+POST_OBJS_FLAGS :=
+'
+		;;
 	3ds)
 		_elf_loader=yes
 		append_var DEFINES "-DUNCACHED_PLUGINS"
--- a/dists/emscripten/README.md
+++ b/dists/emscripten/README.md
@ -0,0 +1,61 @@
+# Building ScummVM for Webassembly
+The [Emscripten](https://emscripten.org/) target provides a script to build ScummVM as a single page browser app.
+> Emscripten is an LLVM/Clang-based compiler that compiles C and C++ source code to WebAssembly for execution in web browsers. 
+
+## Current State
+* All engines compile (though I didn't test all of them), including ResidualVM with WebGL acceleration
+* Audio works and 3rd-party libraries for sound and video decoding are integrated 
+* Proof of concept integration with [BrowserFS](https://github.com/jvilk/browserfs) to download game data lazily when required and to support local savegames 
+
+## How to build for Webassembly
+This folder contains a script to help build scummvm with Emscripten, it automatically downloads the correct emsdk version and also takes care of bundling the data and setting up a few demo games.
+
+### Running `emscripten/build.sh`
+
+`emscripten/build.sh` needs to be run from the root of the project. 
+```
+./dists/emscripten/build.sh libs|configure|make|data|dist|all|clean
+```
+It accepts a single parameter with 7 valid commands:
+- `libs`: Download and compile the required 3rd-party libraries required to build certain engines (libmad, a52dec etc)
+- `configure`: Run the configure script with emconfigure with the recommended settings for a simple demo page 
+- `make`: Run the make scripts with emmake
+- `data`: Download some demos and set up all data require for the demo page 
+- `dist`: Copy all files into a single build-emscripten folder to bring it all together
+- `all`: Run all of the above commands
+- `clean`: Remove all object files, built libs, bundled data etc.
+
+Independent of the command executed, the script sets up a pre-defined emsdk environment in the subfolder `./dists/emscripten/build.sh`
+
+
+## Known Issues + Possible Improvements
+Some ideas for possible improvements:
+
+### Emscripten Optimizations
+- Optimize asyncify behaviour (we only have SDL functions calling wait currently), e.g with https://wiki.libsdl.org/SDL_HINT_EMSCRIPTEN_ASYNCIFY
+- Specify a `ASYNCIFY_ONLY` list to to make asyncify only instrument functions in the call path as described in https://emscripten.org/docs/porting/asyncify.html
+- Don't use asyncify but rewrite main loop to improve performance
+- Shrink code size or execution speed with `-Os` or `-Oz` ( https://emscripten.org/docs/tools_reference/emcc.html#emcc-compiler-optimization-options ) )
+
+
+### Storage Integration:
+- BrowserFS seems abandoned and never did a stable 2.0.0 release. Maybe there's a better way to handle Storage?
+- File Loading Improvements:
+	- Load Assets with HTTP Range Request Headers
+	- Load Assets asynchronously (not blocking) via a worker
+- Add support for save games (and games data?) on personal cloud storage (Dropbox, Google Drive)
+
+### UI Integration:
+- Support resizing canvas is currently broken
+- fix scaling issues / fullscreen not working
+- Build a nice webpage around the canvas
+  - Adapt page padding/background color to theme (black when in game)
+- ScummVM shouldn't be able to "close" (there's no concept for that
+  - Remove "exit" buttons from all menus
+  - Change any programmatic "exits" to cause a restart of Scummvm (or refresh of the page)
+- Pass CLI parameters for ScummVM via URL parameters to allow for "deep-linking" to a specific game
+
+### Other Features + Bugs
+- Bug: vorbis support is broken - parts seems to have been patched out so  -lvorbisfile triggers an error during configure ( https://github.com/emscripten-core/emscripten/pull/9849  doesn't seem to fix this )
+- Bug: Going back to main menu from Grim (and other Residual Games?) messes up the render context and the UI is unusable
+- Todo: Check all disabled features (e.g; TiMidity++) and see if they could be enabled (some might never make sense, e.g. anything requiring MIDI Hardware, Update Checking etc. )
--- a/dists/emscripten/build.sh
+++ b/dists/emscripten/build.sh
@ -0,0 +1,204 @@
+#!/bin/bash
+# print commands
+set -o xtrace
+# exit when any command fails
+set -e
+if [ "$#" -ne 1 ]; then
+  echo "$0: exactly 1 arguments expected: configure, make, data, all"
+  exit 3
+fi
+
+EMSDK_VERSION="2.0.23"
+ROOT_FOLDER=$(pwd)
+DIST_FOLDER="$ROOT_FOLDER/dists/emscripten"
+LIBS_FOLDER="$DIST_FOLDER/libs"
+if [[ ! -d "$DIST_FOLDER" ]]; then
+  echo "/dists/emscripten/ not found. Please make sure to run this script from the root of the project - ./dists/emscripten/build.sh "
+  exit 1
+fi
+if [[ "$1" =~ ^(clean)$ ]]; then
+  make clean
+  rm -rf ./dists/emscripten/libs/build
+  rm -rf ./dists/emscripten/libs/*/
+  rm -rf ./dists/emscripten/emsdk*/
+  find . -name "*.o"
+  find . -name "*.o" -exec rm -rf {} \;
+  find . -name "*.a"
+  find . -name "*.a" -exec rm -rf {} \;
+  find . -name "*.wasm"
+  find . -name "*.wasm" -exec rm -rf {} \;
+  exit 0
+fi
+
+# Activate Emscripten
+if [[ ! -d "$DIST_FOLDER/emsdk-$EMSDK_VERSION" ]]; then
+  echo "$DIST_FOLDER/emsdk-$EMSDK_VERSION not found. Installing Emscripten"
+  cd $DIST_FOLDER
+  wget --content-disposition "https://github.com/emscripten-core/emsdk/archive/${EMSDK_VERSION}.tar.gz"
+  tar xzvf "emsdk-${EMSDK_VERSION}.tar.gz"
+  cd "emsdk-${EMSDK_VERSION}"
+  ./emsdk install ${EMSDK_VERSION}
+  ./emsdk activate ${EMSDK_VERSION}
+fi
+source "$DIST_FOLDER/emsdk-$EMSDK_VERSION/emsdk_env.sh"
+
+# Download + Install Libraries
+echo $LIBS_FOLDER
+mkdir -p "$LIBS_FOLDER"
+if [[ ! -d "$LIBS_FOLDER/build" ]]; then
+  echo "$LIBS_FOLDER/build/ not found. Building plugins..."
+  echo "build libtheora-1.1.1"
+  cd "$LIBS_FOLDER"
+  pwd
+  wget -nc "https://downloads.xiph.org/releases/theora/libtheora-1.1.1.tar.xz"
+  tar -xf libtheora-1.1.1.tar.xz
+  cd "./libtheora-1.1.1/"
+  CFLAGS="-fPIC -s USE_OGG=1 -s USE_VORBIS=1 " emconfigure ./configure --host=wasm32-unknown-none --prefix="$LIBS_FOLDER/build/" --disable-asm
+  emmake make -j 3
+  emmake make install
+
+  echo "building faad2-2.8.8"
+  cd "$LIBS_FOLDER"
+  wget -nc "https://sourceforge.net/projects/faac/files/faad2-src/faad2-2.8.0/faad2-2.8.8.tar.gz"
+  tar -xf faad2-2.8.8.tar.gz
+  cd "./faad2-2.8.8/"
+  CFLAGS="-fPIC" emconfigure ./configure --host=wasm32-unknown-none --prefix="$LIBS_FOLDER/build/"
+  emmake make
+  emmake make install
+
+  echo "building libmad-0.15.1b"
+  cd "$LIBS_FOLDER"
+  # libmad needs patching: https://stackoverflow.com/questions/14015747/gccs-fforce-mem-option
+  wget -nc "http://www.linuxfromscratch.org/patches/blfs/svn/libmad-0.15.1b-fixes-1.patch"
+  wget -nc "https://downloads.sourceforge.net/mad/libmad-0.15.1b.tar.gz"
+  tar -xf libmad-0.15.1b.tar.gz
+  cd "$LIBS_FOLDER/libmad-0.15.1b/"
+  patch -Np1 -i ../libmad-0.15.1b-fixes-1.patch
+  emconfigure ./configure --host=wasm32-unknown-none --prefix="$LIBS_FOLDER/build/" --with-pic --enable-fpm=no
+  emmake make
+  emmake make install
+
+  echo "building libmpeg2-0.5.1"
+  cd "$LIBS_FOLDER"
+  wget -nc "http://libmpeg2.sourceforge.net/files/libmpeg2-0.5.1.tar.gz"
+  tar -xf libmpeg2-0.5.1.tar.gz
+  cd "$LIBS_FOLDER/libmpeg2-0.5.1/"
+
+  CFLAGS="-fPIC" emconfigure ./configure --host=wasm32-unknown-none --prefix="$LIBS_FOLDER/build/" --disable-sdl
+  emmake make
+  emmake make install
+
+  echo "building a52dec-0.7.4"
+  cd "$LIBS_FOLDER"
+  wget -nc "https://liba52.sourceforge.io/files/a52dec-0.7.4.tar.gz"
+  tar -xf a52dec-0.7.4.tar.gz
+  cd "$LIBS_FOLDER/a52dec-0.7.4/"
+  CFLAGS="-fPIC" emconfigure ./configure --host=wasm32-unknown-none --prefix="$LIBS_FOLDER/build/"
+  emmake make -j 3
+  emmake make install
+fi
+
+cd "$ROOT_FOLDER"
+
+## Emscripten configuration (should probably go into the configure file)
+## IMPORTANT: ASYNCIFY WITH -O0 doesnt work (presumably because the stack gets too big)
+export LDFLAGS="-O2 -s ASSERTIONS=1 -s GL_ASSERTIONS=1 -s LLD_REPORT_UNDEFINED -s INITIAL_MEMORY=33554432"
+
+#debugging
+export LDFLAGS="${LDFLAGS}  -gsource-map   --source-map-base \"http://localhost:8080/\" "
+
+# linker flags (bundle JS and default assets)
+export LDFLAGS_LINKER=" --pre-js ./dists/emscripten/pre.js --post-js ./dists/emscripten/post.js --shell-file ./dists/emscripten/custom_shell.html "
+
+if [[ "$1" =~ ^(configure|all)$ ]]; then
+
+  echo "clean, & configure"
+  make clean
+  emconfigure ./configure --enable-debug --enable-verbose-build --host=wasm32-unknown-emscripten \
+    --disable-all-engines \
+    --enable-engine=testbed,scumm,scumm_7_8,grim,monkey4,mohawk,myst,riven,sci32,agos2,sword2,drascula,sky,lure,queen,testbed \
+    --with-theoradec-prefix="$LIBS_FOLDER/build/" \
+    --with-faad-prefix="$LIBS_FOLDER/build/" \
+    --with-mad-prefix="$LIBS_FOLDER/build/" \
+    --with-mpeg2-prefix="$LIBS_FOLDER/build/" \
+    --with-a52-prefix="$LIBS_FOLDER/build/"
+
+  # TODO: enable dynamic linking so we can enable more plugins
+  # https://forums.scummvm.org/viewtopic.php?t=14918
+  # https://github.com/emscripten-core/emscripten/wiki/Linking
+  # https://freecontent.manning.com/dynamic-linking-a-crash-course/
+  # https://iandouglasscott.com/2019/07/18/experimenting-with-webassembly-dynamic-linking-with-clang/
+
+  # HACK: the preload flags break emcc during configure as emcc enables NODERAWFS when run as part of configure
+  # which doesn't support preloading assets, so we have to manually add those after configure to the config.mk file
+  echo "LDFLAGS += ${LDFLAGS_LINKER}" >>config.mk
+
+  # configure currently doesn't clean up all files it created
+  rm scummvm-conf.*
+
+fi
+
+if [[ "$1" =~ ^(data|all)$ ]]; then
+  cd "${ROOT_FOLDER}"
+  rm -rf ./build-emscripten/games/
+  mkdir -p ./build-emscripten/games/
+  cd dists/engine-data
+  ./create-testbed-data.sh
+  mv testbed "${ROOT_FOLDER}/build-emscripten/games/testbed"
+
+  games=true
+  if [ "$games" = true ]; then
+    mkdir -p ./dists/emscripten/games/
+    cd "${ROOT_FOLDER}/dists/emscripten/games/"
+    wget -nc https://downloads.scummvm.org/frs/demos/scumm/ft-dos-demo-en.zip
+    unzip -n ft-dos-demo-en -d "${ROOT_FOLDER}/build-emscripten/games/ft-dos-demo-en/"
+    wget -nc https://downloads.scummvm.org/frs/demos/mohawk/myst-win-demo-en.zip
+    unzip -n myst-win-demo-en.zip -d "${ROOT_FOLDER}/build-emscripten/games/myst-win-demo-en/"
+    wget -nc https://downloads.scummvm.org/frs/demos/mohawk/riven-win-demo-en.zip
+    unzip -n riven-win-demo-en.zip -d "${ROOT_FOLDER}/build-emscripten/games/riven-win-demo-en/" -x DXSETUP/* -x QTWSETUP/*
+    wget -nc https://downloads.scummvm.org/frs/demos/sword2/sword2-win-demo-en.zip
+    unzip -n sword2-win-demo-en.zip -d "${ROOT_FOLDER}/build-emscripten/games/sword2-win-demo-en/"
+    wget -nc https://downloads.scummvm.org/frs/demos/scumm/comi-win-large-demo-en.zip
+    unzip -n comi-win-large-demo-en.zip -d "${ROOT_FOLDER}/build-emscripten/games/comi-win-large-demo-en/"
+    wget -nc https://downloads.scummvm.org/frs/demos/grim/emi-win-demo-en.zip
+    unzip -n emi-win-demo-en.zip -d "${ROOT_FOLDER}/build-emscripten/games/emi-win-demo-en/"
+    wget -nc https://downloads.scummvm.org/frs/demos/grim/grim-win-demo2-en.zip
+    unzip -n grim-win-demo2-en.zip -d "${ROOT_FOLDER}/build-emscripten/games/grim-win-demo2-en/"
+    wget -nc https://downloads.scummvm.org/frs/demos/agos/feeble-dos-ni-demo-en.zip
+    unzip -n feeble-dos-ni-demo-en.zip -d "${ROOT_FOLDER}/build-emscripten/games/feeble-dos-ni-demo-en/"
+    wget -nc https://downloads.scummvm.org/frs/demos/sci/lsl7-dos-demo-en.zip
+    unzip -n lsl7-dos-demo-en.zip -d "${ROOT_FOLDER}/build-emscripten/games/lsl7-dos-demo-en/"
+    wget -nc https://downloads.scummvm.org/frs/demos/sci/phantasmagoria-dos-win-demo-en.zip
+    unzip -n phantasmagoria-dos-win-demo-en -d "${ROOT_FOLDER}/build-emscripten/games/phantasmagoria-dos-win-demo-en/"
+    wget -nc https://downloads.scummvm.org/frs/extras/Beneath%20a%20Steel%20Sky/BASS-Floppy-1.3.zip
+    unzip -n BASS-Floppy-1.3.zip -d "${ROOT_FOLDER}/build-emscripten/games/bass-floppy/"
+    wget -nc https://downloads.scummvm.org/frs/extras/Drascula_%20The%20Vampire%20Strikes%20Back/drascula-1.0.zip
+    unzip -n drascula-1.0.zip -d "${ROOT_FOLDER}/build-emscripten/games/drascula/"
+    wget -nc https://downloads.scummvm.org/frs/extras/Drascula_%20The%20Vampire%20Strikes%20Back/drascula-audio-mp3-2.0.zip
+    unzip -n drascula-audio-mp3-2.0.zip -d "${ROOT_FOLDER}/build-emscripten/games/drascula/"
+    wget -nc https://downloads.scummvm.org/frs/extras/Flight%20of%20the%20Amazon%20Queen/FOTAQ_Floppy.zip
+    unzip -n FOTAQ_Floppy.zip -d "${ROOT_FOLDER}/build-emscripten/games/fotaq-floppy/"
+    wget -nc https://downloads.scummvm.org/frs/extras/Lure%20of%20the%20Temptress/lure-1.1.zip
+    unzip -n lure-1.1.zip -d "${ROOT_FOLDER}/build-emscripten/games/lure/"
+  fi
+
+  cd "${ROOT_FOLDER}//build-emscripten/games/"
+  NODE_DIR=$(dirname $EMSDK_NODE)
+  "$NODE_DIR/npx" -p browserfs make_xhrfs_index >index.json
+fi
+
+if [[ "$1" =~ ^(make|all)$ ]]; then
+  cd "${ROOT_FOLDER}"
+  emmake make
+  emmake make dist-generic
+  # preload data
+  $EMSDK_PYTHON $EMSDK/upstream/emscripten/tools/file_packager.py files.data --preload ./dist-generic/scummvm/data@/ --use-preload-cache --js-output=files.js
+  rm -rf dist-generic/
+fi
+
+if [[ "$1" =~ ^(dist|all)$ ]]; then
+  cd "${ROOT_FOLDER}"
+  mkdir -p build-emscripten
+  mv scummvm.* build-emscripten/
+  mv files.* build-emscripten/
+fi
--- a/dists/emscripten/custom_shell.html
+++ b/dists/emscripten/custom_shell.html
--- a/dists/emscripten/post.js
+++ b/dists/emscripten/post.js
@ -0,0 +1,2 @@
+// Workaround for https://github.com/emscripten-core/emscripten/pull/9803  which results in mouse events not working anymore after context switches
+JSEvents.removeAllHandlersOnTarget = function(){}
--- a/dists/emscripten/pre.js
+++ b/dists/emscripten/pre.js
@ -0,0 +1,7 @@
+Module['arguments'] = [];
+//Module['arguments'].push('--debuglevel=5');
+Module['arguments'].push('--config=/data/local/scummvm.ini');
+//Module['arguments'].push('--add');
+//Module['arguments'].push('--recursive');
+//Module['arguments'].push('--path=/data/games');
+
--- a/engines/grim/grim.cpp
+++ b/engines/grim/grim.cpp
@ -1116,6 +1116,10 @@ void GrimEngine::mainLoop() {
 			g_imuseState = -1;
 		}

+		#if defined(EMSCRIPTEN)
+		// We need to yield regularly to unblock the main thread
+		g_system->delayMillis(10);
+		#endif
 		uint32 endTime = g_system->getMillis();
 		if (startTime > endTime)
 			continue;
--- a/graphics/opengl/framebuffer.cpp
+++ b/graphics/opengl/framebuffer.cpp
@ -158,12 +158,20 @@ void FrameBuffer::init() {
 		glBindRenderbuffer(GL_RENDERBUFFER, 0);
 	} else {
 		glBindRenderbuffer(GL_RENDERBUFFER, _renderBuffers[0]);
+		#if defined(EMSCRIPTEN)
+		// See https://www.khronos.org/registry/webgl/specs/latest/1.0/#FBO_ATTACHMENTS
+		#define GL_DEPTH_STENCIL 0x84F9
+		glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_STENCIL, _texWidth, _texHeight);
+		#define GL_DEPTH_STENCIL_ATTACHMENT 0x821A
+		glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT, GL_RENDERBUFFER, _renderBuffers[0]);
+		#else
 		glRenderbufferStorage(GL_RENDERBUFFER, useDepthComponent24() ? GL_DEPTH_COMPONENT24 : GL_DEPTH_COMPONENT16, _texWidth, _texHeight);
 		glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, _renderBuffers[0]);

 		glBindRenderbuffer(GL_RENDERBUFFER, _renderBuffers[1]);
 		glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8, _texWidth, _texHeight);
 		glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, _renderBuffers[1]);
+		#endif
 		glBindRenderbuffer(GL_RENDERBUFFER, 0);
 	}

--- a/graphics/opengl/shader.cpp
+++ b/graphics/opengl/shader.cpp
@ -33,6 +33,10 @@ namespace OpenGL {
 static const GLchar *readFile(const Common::String &filename) {
 	Common::File file;

+	#if defined(EMSCRIPTEN)
+	// Since we need to bundle all files into data files on Emscripten, we keep all shaders in a different folder
+	SearchMan.addDirectory("ALL_SHADERS", "/", 0, 2);
+	#endif
 	// Allow load shaders from source code directory without install them
 	// It's used for development purpose
 	// FIXME: it's doesn't work with just search subdirs in 'engines'
@ -47,6 +51,9 @@ static const GLchar *readFile(const Common::String &filename) {
 	SearchMan.remove("MYST3_SHADERS");
 	SearchMan.remove("STARK_SHADERS");
 	SearchMan.remove("WINTERMUTE_SHADERS");
+	#if defined(EMSCRIPTEN)
+	SearchMan.remove("ALL_SHADERS");
+	#endif

 	const int32 size = file.size();
 	GLchar *shaderSource = new GLchar[size + 1];