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>

1 files changed, 93 insertions, 0 deletions

diff --git a/os/emscripten/pre.js b/os/emscripten/pre.js
new file mode 100644
index 000000000..5cbd899e0
--- /dev/null
+++ b/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) { });
+    }
+});