Add: support for emscripten (play-OpenTTD-in-the-browser)

Emscripten compiles to WASM, which can be loaded via
HTML / JavaScript. This allows you to play OpenTTD inside a
browser.

Co-authored-by: milek7 <me@milek7.pl>

os/emscripten/Dockerfile

@@ -0,0 +1,4 @@
+FROM emscripten/emsdk
+
+COPY emsdk-liblzma.patch /
+RUN cd /emsdk/upstream/emscripten && patch -p1 < /emsdk-liblzma.patch

os/emscripten/README.md

@@ -0,0 +1,40 @@
+## How to build with Emscripten
+
+Building with Emscripten works with emsdk 2.0.10 and above.
+
+Currently there is no LibLZMA support upstream; for this we suggest to apply
+the provided patch in this folder to your emsdk installation.
+
+For convenience, a Dockerfile is supplied that does this patches for you
+against upstream emsdk docker. Best way to use it:
+
+Build the docker image:
+```
+  docker build -t emsdk-lzma .
+```
+
+Build the host tools first:
+```
+  mkdir build-host
+  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build-host emsdk-lzma cmake .. -DOPTION_TOOLS_ONLY=ON
+  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build-host emsdk-lzma make -j5 tools
+```
+
+Next, build the game with emscripten:
+
+```
+  mkdir build
+  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-lzma emcmake cmake .. -DHOST_BINARY_DIR=$(pwd)/build-host -DCMAKE_BUILD_TYPE=RelWithDebInfo -DOPTION_USE_ASSERTS=OFF
+  docker run -it --rm -v $(pwd):$(pwd) -u $(id -u):$(id -g) --workdir $(pwd)/build emsdk-lzma emmake make -j5
+```
+
+And now you have in your build folder files like "openttd.html".
+
+To run it locally, you would have to start a local webserver, like:
+
+```
+  cd build
+  python3 -m http.server
+````
+
+Now you can play the game via http://127.0.0.1:8000/openttd.html .

os/emscripten/cmake/FindLibLZMA.cmake

@@ -0,0 +1,20 @@
+# LibLZMA is a recent addition to the emscripten SDK, so it is possible
+# someone hasn't updated his SDK yet. Test out if the SDK supports LibLZMA.
+include(CheckCXXSourceCompiles)
+set(CMAKE_REQUIRED_FLAGS "-sUSE_LIBLZMA=1")
+
+check_cxx_source_compiles("
+    #include <lzma.h>
+    int main() { return 0; }"
+    LIBLZMA_FOUND
+)
+
+if (LIBLZMA_FOUND)
+        add_library(LibLZMA::LibLZMA INTERFACE IMPORTED)
+        set_target_properties(LibLZMA::LibLZMA PROPERTIES
+                INTERFACE_COMPILE_OPTIONS "-sUSE_LIBLZMA=1"
+                INTERFACE_LINK_LIBRARIES "-sUSE_LIBLZMA=1"
+        )
+else()
+        message(WARNING "You are using an emscripten SDK without LibLZMA support. Many savegames won't be able to load in OpenTTD. Please apply 'emsdk-liblzma.patch' to your local emsdk installation.")
+endif()

os/emscripten/cmake/FindPNG.cmake

@@ -0,0 +1,7 @@
+add_library(PNG::PNG INTERFACE IMPORTED)
+set_target_properties(PNG::PNG PROPERTIES
+        INTERFACE_COMPILE_OPTIONS "-sUSE_LIBPNG=1"
+        INTERFACE_LINK_LIBRARIES "-sUSE_LIBPNG=1"
+)
+
+set(PNG_FOUND on)

os/emscripten/cmake/FindSDL2.cmake

@@ -0,0 +1,7 @@
+add_library(SDL2::SDL2 INTERFACE IMPORTED)
+set_target_properties(SDL2::SDL2 PROPERTIES
+        INTERFACE_COMPILE_OPTIONS "-sUSE_SDL=2"
+        INTERFACE_LINK_LIBRARIES "-sUSE_SDL=2"
+)
+
+set(SDL2_FOUND on)

os/emscripten/cmake/FindZLIB.cmake

@@ -0,0 +1,7 @@
+add_library(ZLIB::ZLIB INTERFACE IMPORTED)
+set_target_properties(ZLIB::ZLIB PROPERTIES
+        INTERFACE_COMPILE_OPTIONS "-sUSE_ZLIB=1"
+        INTERFACE_LINK_LIBRARIES "-sUSE_ZLIB=1"
+)
+
+set(ZLIB_FOUND on)

os/emscripten/emsdk-liblzma.patch

@@ -0,0 +1,213 @@
+From 90dd4d4c6b1cedec338ff5b375fffca93700f7bc Mon Sep 17 00:00:00 2001
+From: milek7 <me@milek7.pl>
+Date: Tue, 8 Dec 2020 01:03:31 +0100
+Subject: [PATCH] Add liblzma port
+
+---
+Source: https://github.com/emscripten-core/emscripten/pull/12990
+
+Modifed by OpenTTD to have the bare minimum needed to work. Otherwise there
+are constantly conflicts when trying to apply this patch to different versions
+of emsdk.
+
+diff --git a/embuilder.py b/embuilder.py
+index 818262190ed..ab7d5adb7b2 100755
+--- a/embuilder.py
++++ b/embuilder.py
+@@ -60,6 +60,7 @@
+     'harfbuzz',
+     'icu',
+     'libjpeg',
++    'liblzma',
+     'libpng',
+     'ogg',
+     'regal',
+@@ -197,6 +198,8 @@ def main():
+       build_port('ogg', libname('libogg'))
+     elif what == 'libjpeg':
+       build_port('libjpeg', libname('libjpeg'))
++    elif what == 'liblzma':
++      build_port('liblzma', libname('liblzma'))
+     elif what == 'libpng':
+       build_port('libpng', libname('libpng'))
+     elif what == 'sdl2':
+diff --git a/src/settings.js b/src/settings.js
+index 61cd98939ba..be6fcb678c6 100644
+--- a/src/settings.js
++++ b/src/settings.js
+@@ -1197,6 +1197,9 @@ var USE_BZIP2 = 0;
+ // 1 = use libjpeg from emscripten-ports
+ var USE_LIBJPEG = 0;
+
++// 1 = use liblzma from emscripten-ports
++var USE_LIBLZMA = 0;
++
+ // 1 = use libpng from emscripten-ports
+ var USE_LIBPNG = 0;
+
+diff --git a/tools/ports/liblzma.py b/tools/ports/liblzma.py
+new file mode 100644
+index 00000000000..e9567ef36ff
+--- /dev/null
++++ b/tools/ports/liblzma.py
+@@ -0,0 +1,160 @@
++# Copyright 2020 The Emscripten Authors.  All rights reserved.
++# Emscripten is available under two separate licenses, the MIT license and the
++# University of Illinois/NCSA Open Source License.  Both these licenses can be
++# found in the LICENSE file.
++
++import os
++import shutil
++
++VERSION = '5.2.5'
++HASH = '7443674247deda2935220fbc4dfc7665e5bb5a260be8ad858c8bd7d7b9f0f868f04ea45e62eb17c0a5e6a2de7c7500ad2d201e2d668c48ca29bd9eea5a73a3ce'
++
++
++def needed(settings):
++  return settings.USE_LIBLZMA
++
++
++def get(ports, settings, shared):
++  libname = ports.get_lib_name('liblzma')
++  ports.fetch_project('liblzma', 'https://tukaani.org/xz/xz-' + VERSION + '.tar.gz', 'xz-' + VERSION, sha512hash=HASH)
++
++  def create():
++    ports.clear_project_build('liblzma')
++
++    source_path = os.path.join(ports.get_dir(), 'liblzma', 'xz-' + VERSION)
++    dest_path = os.path.join(ports.get_build_dir(), 'liblzma')
++
++    shared.try_delete(dest_path)
++    os.makedirs(dest_path)
++    shutil.rmtree(dest_path, ignore_errors=True)
++    shutil.copytree(source_path, dest_path)
++
++    build_flags = ['-DHAVE_CONFIG_H', '-DTUKLIB_SYMBOL_PREFIX=lzma_', '-fvisibility=hidden']
++    exclude_dirs = ['xzdec', 'xz', 'lzmainfo']
++    exclude_files = ['crc32_small.c', 'crc64_small.c', 'crc32_tablegen.c', 'crc64_tablegen.c', 'price_tablegen.c', 'fastpos_tablegen.c'
++                     'tuklib_exit.c', 'tuklib_mbstr_fw.c', 'tuklib_mbstr_width.c', 'tuklib_open_stdxxx.c', 'tuklib_progname.c']
++    include_dirs_rel = ['../common', 'api', 'common', 'check', 'lz', 'rangecoder', 'lzma', 'delta', 'simple']
++
++    open(os.path.join(dest_path, 'src', 'config.h'), 'w').write(config_h)
++
++    final = os.path.join(dest_path, libname)
++    include_dirs = [os.path.join(dest_path, 'src', 'liblzma', p) for p in include_dirs_rel]
++    ports.build_port(os.path.join(dest_path, 'src'), final, flags=build_flags, exclude_dirs=exclude_dirs, exclude_files=exclude_files, includes=include_dirs)
++
++    ports.install_headers(os.path.join(dest_path, 'src', 'liblzma', 'api'), 'lzma.h')
++    ports.install_headers(os.path.join(dest_path, 'src', 'liblzma', 'api', 'lzma'), '*.h', 'lzma')
++
++    return final
++
++  return [shared.Cache.get(libname, create, what='port')]
++
++
++def clear(ports, settings, shared):
++  shared.Cache.erase_file(ports.get_lib_name('liblzma'))
++
++
++def process_args(ports):
++  return []
++
++
++def show():
++  return 'liblzma (USE_LIBLZMA=1; public domain)'
++
++
++config_h = r'''
++#define ASSUME_RAM 128
++#define ENABLE_NLS 1
++#define HAVE_CHECK_CRC32 1
++#define HAVE_CHECK_CRC64 1
++#define HAVE_CHECK_SHA256 1
++#define HAVE_CLOCK_GETTIME 1
++#define HAVE_DCGETTEXT 1
++#define HAVE_DECL_CLOCK_MONOTONIC 1
++#define HAVE_DECL_PROGRAM_INVOCATION_NAME 1
++#define HAVE_DECODERS 1
++#define HAVE_DECODER_ARM 1
++#define HAVE_DECODER_ARMTHUMB 1
++#define HAVE_DECODER_DELTA 1
++#define HAVE_DECODER_IA64 1
++#define HAVE_DECODER_LZMA1 1
++#define HAVE_DECODER_LZMA2 1
++#define HAVE_DECODER_POWERPC 1
++#define HAVE_DECODER_SPARC 1
++#define HAVE_DECODER_X86 1
++#define HAVE_DLFCN_H 1
++#define HAVE_ENCODERS 1
++#define HAVE_ENCODER_ARM 1
++#define HAVE_ENCODER_ARMTHUMB 1
++#define HAVE_ENCODER_DELTA 1
++#define HAVE_ENCODER_IA64 1
++#define HAVE_ENCODER_LZMA1 1
++#define HAVE_ENCODER_LZMA2 1
++#define HAVE_ENCODER_POWERPC 1
++#define HAVE_ENCODER_SPARC 1
++#define HAVE_ENCODER_X86 1
++#define HAVE_FCNTL_H 1
++#define HAVE_FUTIMENS 1
++#define HAVE_GETOPT_H 1
++#define HAVE_GETOPT_LONG 1
++#define HAVE_GETTEXT 1
++#define HAVE_IMMINTRIN_H 1
++#define HAVE_INTTYPES_H 1
++#define HAVE_LIMITS_H 1
++#define HAVE_MBRTOWC 1
++#define HAVE_MEMORY_H 1
++#define HAVE_MF_BT2 1
++#define HAVE_MF_BT3 1
++#define HAVE_MF_BT4 1
++#define HAVE_MF_HC3 1
++#define HAVE_MF_HC4 1
++#define HAVE_OPTRESET 1
++#define HAVE_POSIX_FADVISE 1
++#define HAVE_PTHREAD_CONDATTR_SETCLOCK 1
++#define HAVE_PTHREAD_PRIO_INHERIT 1
++#define HAVE_STDBOOL_H 1
++#define HAVE_STDINT_H 1
++#define HAVE_STDLIB_H 1
++#define HAVE_STRINGS_H 1
++#define HAVE_STRING_H 1
++#define HAVE_STRUCT_STAT_ST_ATIM_TV_NSEC 1
++#define HAVE_SYS_PARAM_H 1
++#define HAVE_SYS_STAT_H 1
++#define HAVE_SYS_TIME_H 1
++#define HAVE_SYS_TYPES_H 1
++#define HAVE_UINTPTR_T 1
++#define HAVE_UNISTD_H 1
++#define HAVE_VISIBILITY 1
++#define HAVE_WCWIDTH 1
++#define HAVE__BOOL 1
++#define HAVE___BUILTIN_ASSUME_ALIGNED 1
++#define HAVE___BUILTIN_BSWAPXX 1
++#define MYTHREAD_POSIX 1
++#define NDEBUG 1
++#define PACKAGE "xz"
++#define PACKAGE_BUGREPORT "lasse.collin@tukaani.org"
++#define PACKAGE_NAME "XZ Utils"
++#define PACKAGE_STRING "XZ Utils 5.2.5"
++#define PACKAGE_TARNAME "xz"
++#define PACKAGE_VERSION "5.2.5"
++#define SIZEOF_SIZE_T 4
++#define STDC_HEADERS 1
++#define TUKLIB_CPUCORES_SYSCONF 1
++#define TUKLIB_FAST_UNALIGNED_ACCESS 1
++#define TUKLIB_PHYSMEM_SYSCONF 1
++#ifndef _ALL_SOURCE
++# define _ALL_SOURCE 1
++#endif
++#ifndef _GNU_SOURCE
++# define _GNU_SOURCE 1
++#endif
++#ifndef _POSIX_PTHREAD_SEMANTICS
++# define _POSIX_PTHREAD_SEMANTICS 1
++#endif
++#ifndef _TANDEM_SOURCE
++# define _TANDEM_SOURCE 1
++#endif
++#ifndef __EXTENSIONS__
++# define __EXTENSIONS__ 1
++#endif
++#define VERSION "5.2.5"
++'''

os/emscripten/pre.js

@@ -0,0 +1,93 @@
+Module.arguments.push('-mnull', '-snull', '-vsdl:relative_mode');
+Module['websocket'] = { url: function(host, port, proto) {
+    /* openttd.org hosts a WebSocket proxy for the content service. */
+    if (host == "content.openttd.org" && port == 3978 && proto == "tcp") {
+        return "wss://content.openttd.org/";
+    }
+
+    /* Everything else just tries to make a default WebSocket connection.
+     * If you run your own server you can setup your own WebSocket proxy in
+     * front of it and let people connect to your server via the proxy. You
+     * are best to add another "if" statement as above for this. */
+    return null;
+} };
+
+Module.preRun.push(function() {
+    personal_dir = '/home/web_user/.openttd';
+    content_download_dir = personal_dir + '/content_download'
+
+    /* Because of the "-c" above, all user-data is stored in /user_data. */
+    FS.mkdir(personal_dir);
+    FS.mount(IDBFS, {}, personal_dir);
+
+    Module.addRunDependency('syncfs');
+    FS.syncfs(true, function (err) {
+        /* FS.mkdir() tends to fail if parent folders do not exist. */
+        if (!FS.analyzePath(content_download_dir).exists) {
+            FS.mkdir(content_download_dir);
+        }
+        if (!FS.analyzePath(content_download_dir + '/baseset').exists) {
+            FS.mkdir(content_download_dir + '/baseset');
+        }
+
+        /* Check if the OpenGFX baseset is already downloaded. */
+        if (!FS.analyzePath(content_download_dir + '/baseset/opengfx-0.6.0.tar').exists) {
+            window.openttd_downloaded_opengfx = true;
+            FS.createPreloadedFile(content_download_dir + '/baseset', 'opengfx-0.6.0.tar', 'https://installer.cdn.openttd.org/emscripten/opengfx-0.6.0.tar', true, true);
+        } else {
+            /* Fake dependency increase, so the counter is stable. */
+            Module.addRunDependency('opengfx');
+            Module.removeRunDependency('opengfx');
+        }
+
+        Module.removeRunDependency('syncfs');
+    });
+
+    window.openttd_syncfs_shown_warning = false;
+    window.openttd_syncfs = function() {
+        /* Copy the virtual FS to the persistent storage. */
+        FS.syncfs(false, function (err) { });
+
+        /* On first time, warn the user about the volatile behaviour of
+         * persistent storage. */
+        if (!window.openttd_syncfs_shown_warning) {
+            window.openttd_syncfs_shown_warning = true;
+            Module.onWarningFs();
+        }
+    }
+
+    window.openttd_exit = function() {
+        Module.onExit();
+    }
+
+    window.openttd_abort = function() {
+        Module.onAbort();
+    }
+
+    window.openttd_server_list = function() {
+        add_server = Module.cwrap("em_openttd_add_server", null, ["string", "number"]);
+
+        /* Add servers that support WebSocket here. Example:
+         *  add_server("localhost", 3979); */
+    }
+
+    /* https://github.com/emscripten-core/emscripten/pull/12995 implements this
+    * properly. Till that time, we use a polyfill. */
+   SOCKFS.websocket_sock_ops.createPeer_ = SOCKFS.websocket_sock_ops.createPeer;
+   SOCKFS.websocket_sock_ops.createPeer = function(sock, addr, port)
+   {
+       let func = Module['websocket']['url'];
+       Module['websocket']['url'] = func(addr, port, (sock.type == 2) ? 'udp' : 'tcp');
+       let ret = SOCKFS.websocket_sock_ops.createPeer_(sock, addr, port);
+       Module['websocket']['url'] = func;
+       return ret;
+   }
+});
+
+Module.postRun.push(function() {
+    /* Check if we downloaded OpenGFX; if so, sync the virtual FS back to the
+     * IDBFS so OpenGFX is stored persistent. */
+    if (window['openttd_downloaded_opengfx']) {
+        FS.syncfs(false, function (err) { });
+    }
+});