Support XDG Base directory specification for Linux

Ref:
1. https://specifications.freedesktop.org/basedir-spec/latest
2. aria2/aria2@8bc1d37

Author: WhiredPlanck

libaegisub/common/path.cpp

@@ -29,7 +29,8 @@ constexpr std::string_view tokens[] = {
 	"?script",
 	"?temp",
 	"?user",
-	"?video"
+	"?video",
+	"?state"
 };
 
 int find_token(std::string_view str) {
@@ -44,6 +45,7 @@ int find_token(std::string_view str) {
 	case 't' + 'p': idx = 5; break;
 	case 'u' + 'r': idx = 6; break;
 	case 'v' + 'e': idx = 7; break;
+	case 's' + 't': idx = 8; break;
 	default: return -1;
 	}
 	return str.starts_with(tokens[idx]) ? idx : -1;

libaegisub/unix/path.cpp

@@ -41,6 +41,12 @@ std::string home_dir() {
 	throw agi::EnvironmentError("Could not get home directory. Make sure HOME is set.");
 }
 
+std::string xdg_dir(std::string_view token, agi::fs::path const& fallback) {
+	const char *env = getenv(token.data());
+	if (env) return env;
+	return fallback.string();
+} 
+
 #ifdef APPIMAGE_BUILD
 std::string exe_dir() {
 	char *exe, *dir;
@@ -70,12 +76,32 @@ namespace agi {
 void Path::FillPlatformSpecificPaths() {
 #ifndef __APPLE__
 	agi::fs::path home = home_dir();
-	SetToken("?user", home/".aegisub");
-	SetToken("?local", home/".aegisub");
+	agi::fs::path old_root = home/".aegisub";
+
+	agi::fs::path xdg_config = xdg_dir("XDG_CONFIG_HOME", home/".config");
+	agi::fs::path xdg_cache = xdg_dir("XDG_CACHE_HOME", home/"cache");
+	agi::fs::path xdg_state = xdg_dir("XDG_STATE_HOME", home/".local/state");
+	agi::fs::path xdg_data = xdg_dir("XDG_DATA_HOME", home/".local/share");
+
+	if (agi::fs::DirectoryExists(old_root)) {
+		SetToken("?user", old_root);
+		SetToken("?local", old_root);
+		SetToken("?state", old_root);
+	} else {
+		SetToken("?user", xdg_config/"aegisub");
+		SetToken("?local", xdg_cache/"aegisub");
+		SetToken("?state", xdg_state/"aegisub");
+	}
 
 #ifdef APPIMAGE_BUILD
 	agi::fs::path data = exe_dir();
-	if (data == "") data = home/".aegisub";
+	if (data == "") {
+		if (agi::fs::DirectoryExists(old_root)) {
+		    data = old_root;
+		} else {
+			data = xdg_data/"aegisub"
+		}
+	}
 	SetToken("?data", data);
 	SetToken("?dictionary", Decode("?data/dictionaries"));
 #else
@@ -87,6 +113,7 @@ void Path::FillPlatformSpecificPaths() {
 	agi::fs::path app_support = agi::util::GetApplicationSupportDirectory();
 	SetToken("?user", app_support/"Aegisub");
 	SetToken("?local", app_support/"Aegisub");
+	SetToken("?state", app_support/"Aegisub");
 	SetToken("?data", agi::util::GetBundleSharedSupportDirectory());
 	SetToken("?dictionary", Decode("?data/dictionaries"));
 #endif

libaegisub/windows/path_win.cpp

@@ -45,6 +45,7 @@ void Path::FillPlatformSpecificPaths() {
 
 	SetToken("?user", WinGetFolderPath(CSIDL_APPDATA)/"Aegisub");
 	SetToken("?local", WinGetFolderPath(CSIDL_LOCAL_APPDATA)/"Aegisub");
+	SetToken("?state", WinGetFolderPath(CSIDL_APPDATA)/"Aegisub");
 
 	std::wstring filename(MAX_PATH + 1, L'\0');
 	while (static_cast<DWORD>(filename.size()) == GetModuleFileNameW(nullptr, &filename[0], filename.size()))

src/dialog_autosave.cpp

@@ -92,7 +92,7 @@ DialogAutosave::DialogAutosave(wxWindow *parent)
 	std::map<wxString, AutosaveFile> files_map;
 	Populate(files_map, OPT_GET("Path/Auto/Save")->GetString(), ".AUTOSAVE.ass", "%s");
 	Populate(files_map, OPT_GET("Path/Auto/Backup")->GetString(), ".ORIGINAL.ass", _("%s [ORIGINAL BACKUP]"));
-	Populate(files_map, "?user/recovered", ".ass", _("%s [RECOVERED]"));
+	Populate(files_map, "?state/recovered", ".ass", _("%s [RECOVERED]"));
 
 	for (auto& file : files_map | boost::adaptors::map_values)
 		files.emplace_back(std::move(file));

src/dialog_shift_times.cpp

@@ -133,7 +133,7 @@ static wxString get_history_string(json::Object &obj) {
 DialogShiftTimes::DialogShiftTimes(agi::Context *context)
 : wxDialog(context->parent, -1, _("Shift Times"))
 , context(context)
-, history_filename(config::path->Decode("?user/shift_history.json"))
+, history_filename(config::path->Decode("?state/shift_history.json"))
 , timecodes_loaded_slot(context->project->AddTimecodesListener(&DialogShiftTimes::OnTimecodesLoaded, this))
 , selected_set_changed_slot(context->selectionController->AddSelectionListener(&DialogShiftTimes::OnSelectedSetChanged, this))
 {

src/libresrc/default_config.json

@@ -285,8 +285,8 @@
 
 	"Path" : {
 		"Auto" : {
-			"Backup" : "?user/autoback",
-			"Save" : "?user/autosave"
+			"Backup" : "?state/autoback",
+			"Save" : "?state/autosave"
 		},
 		"Automation" : {
 			"Autoload" : "?user/automation/autoload/|?data/automation/autoload/",

src/main.cpp

@@ -154,6 +154,7 @@ bool AegisubApp::OnInit() {
 		// Local config, make ?user mean ?data so all user settings are placed in install dir
 		config::path->SetToken("?user", config::path->Decode("?data"));
 		config::path->SetToken("?local", config::path->Decode("?data"));
+		config::path->SetToken("?state", config::path->Decode("?data"));
 		crash_writer::Initialize(config::path->Decode("?user"));
 	} catch (agi::fs::FileSystemError const&) {
 		// File doesn't exist or we can't read it
@@ -162,7 +163,7 @@ bool AegisubApp::OnInit() {
 #endif
 
 	StartupLog("Create log writer");
-	auto path_log = config::path->Decode("?user/log/");
+	auto path_log = config::path->Decode("?state/log/");
 	agi::fs::CreateDirectory(path_log);
 	agi::log::log->Subscribe(std::make_unique<agi::log::JsonEmitter>(path_log));
 	CleanCache(path_log, "*.json", 10, 100);
@@ -373,7 +374,7 @@ void AegisubApp::UnhandledException(bool stackWalk) {
 		auto c = frame->context.get();
 		if (!c || !c->ass || !c->subsController) continue;
 
-		path = config::path->Decode("?user/recovered");
+		path = config::path->Decode("?state/recovered");
 		agi::fs::CreateDirectory(path);
 
 		auto filename = c->subsController->Filename().stem();