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>

5 files changed, 73 insertions, 4 deletions

diff --git a/src/network/core/address.cpp b/src/network/core/address.cpp
index c2fecc7ff..1aaa0b5fb 100644
--- a/src/network/core/address.cpp
+++ b/src/network/core/address.cpp
@@ -299,7 +299,15 @@ static SOCKET ConnectLoopProc(addrinfo *runp)
 
 	if (!SetNoDelay(sock)) DEBUG(net, 1, "[%s] setting TCP_NODELAY failed", type);
 
-	if (connect(sock, runp->ai_addr, (int)runp->ai_addrlen) != 0) {
+	int err = connect(sock, runp->ai_addr, (int)runp->ai_addrlen);
+#ifdef __EMSCRIPTEN__
+	/* Emscripten is asynchronous, and as such a connect() is still in
+	 * progress by the time the call returns. */
+	if (err != 0 && errno != EINPROGRESS)
+#else
+	if (err != 0)
+#endif
+	{
 		DEBUG(net, 1, "[%s] could not connect %s socket: %s", type, family, strerror(errno));
 		closesocket(sock);
 		return INVALID_SOCKET;
diff --git a/src/network/core/os_abstraction.h b/src/network/core/os_abstraction.h
index 01ab68b27..be8b8f919 100644
--- a/src/network/core/os_abstraction.h
+++ b/src/network/core/os_abstraction.h
@@ -83,6 +83,16 @@ typedef unsigned long in_addr_t;
 #	include <errno.h>
 #	include <sys/time.h>
 #	include <netdb.h>
+
+#   if defined(__EMSCRIPTEN__)
+/* Emscripten doesn't support AI_ADDRCONFIG and errors out on it. */
+#		undef AI_ADDRCONFIG
+#		define AI_ADDRCONFIG 0
+/* Emscripten says it supports FD_SETSIZE fds, but it really only supports 64.
+ * https://github.com/emscripten-core/emscripten/issues/1711 */
+#		undef FD_SETSIZE
+#		define FD_SETSIZE 64
+#   endif
 #endif /* UNIX */
 
 /* OS/2 stuff */
@@ -148,12 +158,16 @@ typedef unsigned long in_addr_t;
  */
 static inline bool SetNonBlocking(SOCKET d)
 {
-#ifdef _WIN32
-	u_long nonblocking = 1;
+#ifdef __EMSCRIPTEN__
+	return true;
 #else
+#	ifdef _WIN32
+	u_long nonblocking = 1;
+#	else
 	int nonblocking = 1;
-#endif
+#	endif
 	return ioctlsocket(d, FIONBIO, &nonblocking) == 0;
+#endif
 }
 
 /**
@@ -163,10 +177,14 @@ static inline bool SetNonBlocking(SOCKET d)
  */
 static inline bool SetNoDelay(SOCKET d)
 {
+#ifdef __EMSCRIPTEN__
+	return true;
+#else
 	/* XXX should this be done at all? */
 	int b = 1;
 	/* The (const char*) cast is needed for windows */
 	return setsockopt(d, IPPROTO_TCP, TCP_NODELAY, (const char*)&b, sizeof(b)) == 0;
+#endif
 }
 
 /* Make sure these structures have the size we expect them to be */
diff --git a/src/network/network.cpp b/src/network/network.cpp
index 0e3d08630..a100b6b95 100644
--- a/src/network/network.cpp
+++ b/src/network/network.cpp
@@ -1154,3 +1154,14 @@ bool IsNetworkCompatibleVersion(const char *other)
 	const char *hash2 = ExtractNetworkRevisionHash(other);
 	return hash1 && hash2 && (strncmp(hash1, hash2, GITHASH_SUFFIX_LEN) == 0);
 }
+
+#ifdef __EMSCRIPTEN__
+extern "C" {
+
+void CDECL em_openttd_add_server(const char *host, int port)
+{
+	NetworkUDPQueryServer(NetworkAddress(host, port), true);
+}
+
+}
+#endif
diff --git a/src/network/network_content.cpp b/src/network/network_content.cpp
index 5e401d3e9..0140d3ef2 100644
--- a/src/network/network_content.cpp
+++ b/src/network/network_content.cpp
@@ -23,6 +23,10 @@
 #include <zlib.h>
 #endif
 
+#ifdef __EMSCRIPTEN__
+#	include <emscripten.h>
+#endif
+
 #include "../safeguards.h"
 
 extern bool HasScenario(const ContentInfo *ci, bool md5sum);
@@ -289,6 +293,13 @@ void ClientNetworkContentSocketHandler::DownloadSelectedContent(uint &files, uin
 {
 	bytes = 0;
 
+#ifdef __EMSCRIPTEN__
+	/* Emscripten is loaded via an HTTPS connection. As such, it is very
+	 * difficult to make HTTP connections. So always use the TCP method of
+	 * downloading content. */
+	fallback = true;
+#endif
+
 	ContentIDList content;
 	for (const ContentInfo *ci : this->infos) {
 		if (!ci->IsSelected() || ci->state == ContentInfo::ALREADY_HERE) continue;
@@ -535,6 +546,10 @@ void ClientNetworkContentSocketHandler::AfterDownload()
 			unlink(GetFullFilename(this->curInfo, false));
 		}
 
+#ifdef __EMSCRIPTEN__
+		EM_ASM(if (window["openttd_syncfs"]) openttd_syncfs());
+#endif
+
 		this->OnDownloadComplete(this->curInfo->id);
 	} else {
 		ShowErrorMessage(STR_CONTENT_ERROR_COULD_NOT_EXTRACT, INVALID_STRING_ID, WL_ERROR);
diff --git a/src/network/network_gui.cpp b/src/network/network_gui.cpp
index c430c47e5..47bf8fb69 100644
--- a/src/network/network_gui.cpp
+++ b/src/network/network_gui.cpp
@@ -39,6 +39,9 @@
 
 #include "../safeguards.h"
 
+#ifdef __EMSCRIPTEN__
+#	include <emscripten.h>
+#endif
 
 static void ShowNetworkStartServerWindow();
 static void ShowNetworkLobbyWindow(NetworkGameList *ngl);
@@ -475,6 +478,14 @@ public:
 		this->filter_editbox.cancel_button = QueryString::ACTION_CLEAR;
 		this->SetFocusedWidget(WID_NG_FILTER);
 
+		/* As the master-server doesn't support "websocket" servers yet, we
+		 * let "os/emscripten/pre.js" hardcode a list of servers people can
+		 * join. This means the serverlist is curated for now, but it is the
+		 * best we can offer. */
+#ifdef __EMSCRIPTEN__
+		EM_ASM(if (window["openttd_server_list"]) openttd_server_list());
+#endif
+
 		this->last_joined = NetworkGameListAddItem(NetworkAddress(_settings_client.network.last_host, _settings_client.network.last_port));
 		this->server = this->last_joined;
 		if (this->last_joined != nullptr) NetworkUDPQueryServer(this->last_joined->address);
@@ -615,6 +626,12 @@ public:
 		this->GetWidget<NWidgetStacked>(WID_NG_NEWGRF_SEL)->SetDisplayedPlane(sel == nullptr || !sel->online || sel->info.grfconfig == nullptr);
 		this->GetWidget<NWidgetStacked>(WID_NG_NEWGRF_MISSING_SEL)->SetDisplayedPlane(sel == nullptr || !sel->online || sel->info.grfconfig == nullptr || !sel->info.version_compatible || sel->info.compatible);
 
+#ifdef __EMSCRIPTEN__
+		this->SetWidgetDisabledState(WID_NG_FIND, true);
+		this->SetWidgetDisabledState(WID_NG_ADD, true);
+		this->SetWidgetDisabledState(WID_NG_START, true);
+#endif
+
 		this->DrawWidgets();
 	}