Emscripten: Support persistent storage

meson.build

@@ -209,7 +209,10 @@ if host_platform == 'emscripten'
 		'-s', 'WASM=1',
 		'-s', 'ALLOW_MEMORY_GROWTH=1',
 		'-s', 'FORCE_FILESYSTEM=1',
-		'-s', 'EXIT_RUNTIME=1',
+		'-s', 'EXIT_RUNTIME=0',
+		'-s', 'EXPORTED_RUNTIME_METHODS=ccall,cwrap',
+		'-s', 'FS_DEBUG',
+		'-lidbfs.js',
 	]
 	emcc_args = [
 		'-s', 'USE_SDL=2',

src/PowderToy.cpp

@@ -182,6 +182,11 @@ static std::unique_ptr<ExplicitSingletons> explicitSingletons;
 int main(int argc, char *argv[])
 {
 	Platform::SetupCrt();
+	return Platform::InvokeMain(argc, argv);
+}
+
+int Main(int argc, char *argv[])
+{
 	Platform::Atexit([]() {
 		SaveWindowPosition();
 		// Unregister dodgy error handlers so they don't try to show the blue screen when the window is closed
@@ -254,22 +259,22 @@ int main(int argc, char * argv[])
 	}
 	else
 	{
-		auto ddir = std::unique_ptr<char, decltype(&SDL_free)>(SDL_GetPrefPath(NULL, APPDATA), SDL_free);
+		auto ddir = Platform::DefaultDdir();
 		if (!Platform::FileExists("powder.pref"))
 		{
-			if (ddir)
+			if (ddir.size())
 			{
-				if (!Platform::ChangeDir(ddir.get()))
+				if (!Platform::ChangeDir(ddir))
 				{
 					perror("failed to chdir to default ddir");
-					ddir.reset();
+					ddir = {};
 				}
 			}
 		}
 
-		if (ddir)
+		if (ddir.size())
 		{
-			Platform::sharedCwd = ddir.get();
+			Platform::sharedCwd = ddir;
 		}
 	}
 	// We're now in the correct directory, time to get prefs.

src/PowderToySDLEmscripten.cpp

@@ -3,12 +3,23 @@
 #include <emscripten.h>
 #include <iostream>
 
+namespace Platform
+{
+	void MaybeTriggerSyncFs();
+}
+
+static void MainLoopBody()
+{
+	EngineProcess();
+	Platform::MaybeTriggerSyncFs();
+}
+
 void SetFpsLimit(FpsLimit newFpsLimit)
 {
 	static bool mainLoopSet = false;
 	if (!mainLoopSet)
 	{
-		emscripten_set_main_loop(EngineProcess, 0, 0);
+		emscripten_set_main_loop(MainLoopBody, 0, 0);
 		mainLoopSet = true;
 	}
 	if (auto *fpsLimitVsync = std::get_if<FpsLimitVsync>(&newFpsLimit))
@@ -28,8 +39,9 @@ void SetFpsLimit(FpsLimit newFpsLimit)
 	}
 }
 
+// Is actually only called once at startup, the real main loop body is MainLoopBody.
 void MainLoop()
 {
 	SetFpsLimit(ui::Engine::Ref().GetFpsLimit());
-	EngineProcess();
+	MainLoopBody();
 }

src/client/http/requestmanager/Emscripten.cpp

@@ -17,7 +17,7 @@ namespace http
 	};
 }
 
-extern "C" void RequestManager_UpdateRequestStatusThunk(http::RequestHandleHttp *handle);
+EMSCRIPTEN_KEEPALIVE extern "C" void RequestManager_UpdateRequestStatusThunk(http::RequestHandleHttp *handle);
 
 namespace http
 {

src/client/http/requestmanager/meson.build

@@ -6,10 +6,6 @@ if not enable_http
 	client_files += files('Null.cpp')
 elif host_platform == 'emscripten'
 	client_files += files('Emscripten.cpp')
-	project_link_args += [
-		'-s', 'EXPORTED_FUNCTIONS=_main,_RequestManager_UpdateRequestStatusThunk',
-		'-s', 'EXPORTED_RUNTIME_METHODS=cwrap',
-	]
 else
 	client_files += files('Libcurl.cpp')
 endif

src/common/platform/Android.cpp

@@ -24,4 +24,8 @@ bool CanUpdate()
 {
 	return false;
 }
+
+void SetupCrt()
+{
+}
 }

src/common/platform/Darwin.cpp

@@ -48,4 +48,8 @@ bool CanUpdate()
 {
 	return false;
 }
+
+void SetupCrt()
+{
+}
 }

src/common/platform/DdirCommon.cpp

@@ -0,0 +1,14 @@
+#include "Platform.h"
+#include "common/String.h"
+#include "Config.h"
+#include <SDL.h>
+#include <memory>
+
+namespace Platform
+{
+ByteString DefaultDdir()
+{
+	auto ddir = std::unique_ptr<char, decltype(&SDL_free)>(SDL_GetPrefPath(NULL, APPDATA), SDL_free);
+	return ddir.get();
+}
+}

src/common/platform/Emscripten.cpp

@@ -1,5 +1,17 @@
 #include "Platform.h"
 #include <ctime>
+#include <emscripten.h>
+#include <emscripten/threading.h>
+#include <atomic>
+#include <iostream>
+
+static std::atomic<bool> shouldSyncFs = false;
+static bool syncFsInFlight = false;
+
+EMSCRIPTEN_KEEPALIVE extern "C" void Platform_SyncFsDone()
+{
+	syncFsInFlight = false;
+}
 
 namespace Platform
 {
@@ -37,4 +49,84 @@ void Atexit(ExitFunc exitFunc)
 void Exit(int code)
 {
 }
+
+ByteString DefaultDdir()
+{
+	return "/powder";
+}
+
+int InvokeMain(int argc, char *argv[])
+{
+	EM_ASM({
+		FS.syncfs(true, () => {
+			Module.ccall('MainJs', 'number', [ 'number', 'number' ], [ $0, $1 ]);
+		});
+	}, argc, argv);
+	return 0;
+}
+
+void MaybeTriggerSyncFs()
+{
+	if (!syncFsInFlight && shouldSyncFs.exchange(false, std::memory_order_relaxed))
+	{
+		std::cerr << "invoking FS.syncfs" << std::endl;
+		syncFsInFlight = true;
+		EM_ASM({
+			FS.syncfs(false, err => {
+				if (err) {
+					console.error(err);
+				}
+				Module.ccall('Platform_SyncFsDone', null, [], []);
+			});
+		});
+	}
+}
+}
+
+EMSCRIPTEN_KEEPALIVE extern "C" int MainJs(int argc, char *argv[])
+{
+	return Main(argc, argv);
+}
+
+EMSCRIPTEN_KEEPALIVE extern "C" void Platform_ShouldSyncFs()
+{
+	shouldSyncFs.store(true, std::memory_order_relaxed);
+}
+
+namespace Platform
+{
+	void SetupCrt()
+	{
+		EM_ASM({
+			let ddir = UTF8ToString($0);
+			let prefix = ddir + '/';
+			let shouldSyncFs = Module.cwrap(
+				'Platform_ShouldSyncFs',
+				null,
+				[]
+			);
+			FS.trackingDelegate['onMovePath'] = function(oldpath, newpath) {
+				if (oldpath.startsWith(prefix) || newpath.startsWith(prefix)) {
+					shouldSyncFs();
+				}
+			};
+			FS.trackingDelegate['onDeletePath'] = function(path) {
+				if (path.startsWith(prefix)) {
+					shouldSyncFs();
+				}
+			};
+			FS.trackingDelegate['onWriteToFile'] = function(path, bytesWritten) {
+				if (path.startsWith(prefix)) {
+					shouldSyncFs();
+				}
+			};
+			FS.trackingDelegate['onMakeDirectory'] = function(path, mode) {
+				if (path.startsWith(prefix)) {
+					shouldSyncFs();
+				}
+			};
+			FS.mkdir(ddir);
+			FS.mount(IDBFS, {}, ddir);
+		}, DefaultDdir().c_str());
+	}
 }

src/common/platform/Linux.cpp

@@ -109,4 +109,8 @@ bool Install()
 	}
 	return ok;
 }
+
+void SetupCrt()
+{
+}
 }

src/common/platform/MainCommon.cpp

@@ -0,0 +1,9 @@
+#include "Platform.h"
+
+namespace Platform
+{
+int InvokeMain(int argc, char *argv[])
+{
+	return Main(argc, argv);
+}
+}

src/common/platform/Null.cpp

@@ -11,4 +11,8 @@ bool CanUpdate()
 {
 	return false;
 }
+
+void SetupCrt()
+{
+}
 }

src/common/platform/Platform.h

@@ -62,4 +62,10 @@ namespace Platform
 	using ExitFunc = void (*)();
 	void Atexit(ExitFunc exitFunc);
 	void Exit(int code);
+
+	ByteString DefaultDdir();
+
+	int InvokeMain(int argc, char *argv[]);
 }
+
+extern "C" int Main(int argc, char *argv[]);

src/common/platform/Posix.cpp

@@ -218,8 +218,4 @@ bool UpdateFinish()
 void UpdateCleanup()
 {
 }
-
-void SetupCrt()
-{
-}
 }

src/common/platform/meson.build

@@ -12,6 +12,10 @@ if host_platform == 'windows'
 		'Windows.cpp',
 		'ExitCommon.cpp',
 	)
+	powder_files += files(
+		'MainCommon.cpp',
+		'DdirCommon.cpp',
+	)
 elif host_platform == 'darwin'
 	can_install_enforce_no = true
 	common_files += files(
@@ -19,6 +23,10 @@ elif host_platform == 'darwin'
 		'Posix.cpp',
 		'ExitCommon.cpp',
 	)
+	powder_files += files(
+		'MainCommon.cpp',
+		'DdirCommon.cpp',
+	)
 elif host_platform == 'android'
 	can_install_enforce_no = true
 	common_files += files(
@@ -26,6 +34,10 @@ elif host_platform == 'android'
 		'Posix.cpp',
 		'ExitCommon.cpp',
 	)
+	powder_files += files(
+		'MainCommon.cpp',
+		'DdirCommon.cpp',
+	)
 elif host_platform == 'emscripten'
 	use_bluescreen = false
 	can_install_enforce_no = true
@@ -41,6 +53,10 @@ elif host_platform == 'linux'
 		'Posix.cpp',
 		'ExitCommon.cpp',
 	)
+	powder_files += files(
+		'MainCommon.cpp',
+		'DdirCommon.cpp',
+	)
 else
 	can_install_enforce_no = true
 	common_files += files(
@@ -48,6 +64,10 @@ else
 		'Posix.cpp',
 		'ExitCommon.cpp',
 	)
+	powder_files += files(
+		'MainCommon.cpp',
+		'DdirCommon.cpp',
+	)
 endif
 conf_data.set('SET_WINDOW_ICON', set_window_icon ? 'true' : 'false')
 conf_data.set('PATH_SEP_CHAR', path_sep_char)