feat: expose root paths as both UTF-8 and ACP

The standard encoding for all the top level paths (base, script, user)
in SimpleGraphic is UTF-8. For some purposes it's useful to know if the
path can be expressed in the user's active codepage as well, the updater
can use it to form absolute paths that the OS understands.

As the user path is fallible, we also expose a human-readable reason as
to why it could not be obtained.

All paths are made weakly canonical rather than fully canonical as the
full flavour requires paths to fully exist.

Author: zao

engine/system/sys_main.h

@@ -69,6 +69,7 @@ class sys_IMain {
 	int			processorCount = 0;
 	std::filesystem::path basePath;
 	std::optional<std::filesystem::path> userPath;
+	std::optional<std::string> userPathReason;
 
 	virtual int		GetTime() = 0;
 	virtual void	Sleep(int msec) = 0;

engine/system/win/sys_main.cpp

@@ -564,9 +564,9 @@ std::filesystem::path FindBasePath()
 	progPath = basePath.data();
 #elif __linux__
 	char basePath[PATH_MAX];
-    ssize_t len = ::readlink("/proc/self/exe", basePath, sizeof(basePath));
-    if (len == -1 || len == sizeof(basePath))
-    	len = 0;
+	ssize_t len = ::readlink("/proc/self/exe", basePath, sizeof(basePath));
+	if (len == -1 || len == sizeof(basePath))
+		len = 0;
 	basePath[len] = '\0';
 	progPath = basePath;
 #elif __APPLE__ && __MACH__
@@ -575,34 +575,34 @@ std::filesystem::path FindBasePath()
 	proc_pidpath(pid, basePath, sizeof(basePath));
 	progPath = basePath;
 #endif
-	progPath = canonical(progPath);
+	progPath = weakly_canonical(progPath);
 	return progPath.parent_path();
 }
 
-std::optional<std::filesystem::path> FindUserPath()
+std::tuple<std::optional<std::filesystem::path>, std::optional<std::string>> FindUserPath()
 {
 #ifdef _WIN32
-    PWSTR osPath{};
-    HRESULT hr = SHGetKnownFolderPath(FOLDERID_Documents, KF_FLAG_DEFAULT, nullptr, &osPath);
+	PWSTR osPath{};
+	HRESULT hr = SHGetKnownFolderPath(FOLDERID_Documents, KF_FLAG_DEFAULT, nullptr, &osPath);
 	if (FAILED(hr)) {
 		// The path may be inaccessible due to malfunctioning cloud providers.
 		CoTaskMemFree(osPath);
-		return {};
+		return { {}, "Could not obtain Documents path from Windows" };
 	}
 	std::wstring pathStr = osPath;
 	CoTaskMemFree(osPath);
 	std::filesystem::path path(pathStr);
-	return canonical(path);
+	return { weakly_canonical(path), {} };
 #else
-    if (char const* data_home_path = getenv("XDG_DATA_HOME")) {
-        return data_home_path;
-    }
-    if (char const* home_path = getenv("HOME")) {
-        return std::filesystem::path(home_path) / ".local/share";
-    }
-    uid_t uid = getuid();
-    struct passwd *pw = getpwuid(uid);
-    return std::filesystem::path(pw->pw_dir) / ".local/share";
+	if (char const* data_home_path = getenv("XDG_DATA_HOME")) {
+		return { data_home_path, {} };
+	}
+	if (char const* home_path = getenv("HOME")) {
+		return { std::filesystem::path(home_path) / ".local/share", {} };
+	}
+	uid_t uid = getuid();
+	struct passwd *pw = getpwuid(uid);
+	return { std::filesystem::path(pw->pw_dir) / ".local/share", {} };
 #endif
 }
 
@@ -628,7 +628,7 @@ sys_main_c::sys_main_c()
 
 	// Set the local system information
 	basePath = FindBasePath();
-	userPath = FindUserPath();
+	std::tie(userPath, userPathReason) = FindUserPath();
 }
 
 bool sys_main_c::Run(int argc, char** argv)

ui_api.cpp

@@ -85,9 +85,9 @@
 ** compressed = Deflate(uncompressed)
 ** uncompressed = Inflate(compressed)
 ** msec = GetTime()
-** path = GetScriptPath()
-** path = GetRuntimePath()
-** path = GetUserPath() -- may return nil if the user path could not be determined
+** path[, pathACP[, err]] = GetScriptPath()
+** path[, pathACP[, err]] = GetRuntimePath()
+** path[, pathACP[, err]] = GetUserPath() -- may return nil if the user path could not be determined
 ** SetWorkDir("<path>")
 ** path = GetWorkDir()
 ** ssID = LaunchSubScript("<scriptText>", "<funcList>", "<subList>"[, ...])
@@ -1544,25 +1544,63 @@ static int l_GetScriptPath(lua_State* L)
 {
 	ui_main_c* ui = GetUIPtr(L);
 	lua_pushstring(L, ui->scriptPath.generic_u8string().c_str());
-	return 1;
+	try
+	{
+		lua_pushstring(L, ui->scriptPath.generic_string().c_str());
+		return 2;
+	}
+	catch (std::exception& e)
+	{
+		lua_pushnil(L);
+		lua_pushstring(L, e.what());
+		return 3;
+	}
 }
 
 static int l_GetRuntimePath(lua_State* L)
 {
 	ui_main_c* ui = GetUIPtr(L);
 	lua_pushstring(L, ui->sys->basePath.generic_u8string().c_str());
-	return 1;
+	try
+	{
+		lua_pushstring(L, ui->sys->basePath.generic_string().c_str());
+		return 2;
+	}
+	catch (std::exception& e)
+	{
+		lua_pushnil(L);
+		lua_pushstring(L, e.what());
+		return 3;
+	}
 }
 
 static int l_GetUserPath(lua_State* L)
 {
 	ui_main_c* ui = GetUIPtr(L);
 	auto& userPath = ui->sys->userPath;
-	if (userPath) {
-		lua_pushstring(L, userPath->generic_u8string().c_str());
-		return 1;
+	if (!userPath) {
+		lua_pushnil(L);
+		lua_pushnil(L);
+		if (auto& reason = ui->sys->userPathReason)
+		{
+			lua_pushstring(L, reason->c_str());
+			return 3;
+		}
+		return 2;
+	}
+
+	lua_pushstring(L, userPath->generic_u8string().c_str());
+	try
+	{
+		lua_pushstring(L, userPath->generic_string().c_str());
+		return 2;
+	}
+	catch (std::exception& e)
+	{
+		lua_pushnil(L);
+		lua_pushstring(L, e.what());
+		return 3;
 	}
-	return 0;
 }
 
 static int l_MakeDir(lua_State* L)