Deal gracefully with the selector being started on a non-existent dir

If directory browsing is enabled, fall back to the closest existing
parent directory. If directory browsing is disabled, show empty list.

src/filelister.cpp

@@ -63,7 +63,7 @@ static void moveNames(set<string, case_less>&& from, vector<string>& to)
 	to.shrink_to_fit();
 }
 
-void FileLister::browse(const string& path, bool clean)
+bool FileLister::browse(const string& path, bool clean)
 {
 	if (clean) {
 		directories.clear();
@@ -79,7 +79,7 @@ void FileLister::browse(const string& path, bool clean)
 		if (errno != ENOENT) {
 			ERROR("Unable to open directory: %s\n", slashedPath.c_str());
 		}
-		return;
+		return false;
 	}
 
 	set<string, case_less> directorySet;
@@ -157,6 +157,8 @@ void FileLister::browse(const string& path, bool clean)
 		files.clear();
 		moveNames(move(fileSet), files);
 	}
+
+	return true;
 }
 
 string FileLister::operator[](uint x)

src/filelister.h

@@ -33,7 +33,14 @@ private:
 
 public:
 	FileLister();
-	void browse(const std::string& path, bool clean = true);
+
+	/**
+	 * Scans the given directory.
+	 * @param clean If true, start a new result set, if false add to the
+	 *   results from the previous scan.
+	 * @return True iff the given directory could be opened.
+	 */
+	bool browse(const std::string& path, bool clean = true);
 
 	unsigned int size() { return files.size() + directories.size(); }
 	unsigned int dirCount() { return directories.size(); }

src/selector.cpp

@@ -53,7 +53,10 @@ int Selector::exec(int startSelection) {
 	FileLister fl;
 	fl.setShowDirectories(showDirectories);
 	fl.setFilter(link.getSelectorFilter());
-	prepare(fl);
+	while (!prepare(fl) && showDirectories && dir != "/") {
+		// The given directory could not be opened; try parent.
+		dir = parentDir(dir);
+	}
 
 	OffscreenSurface bg(*gmenu2x->bg);
 	drawTitleIcon(bg, link.getIconPath(), true);
@@ -185,15 +188,15 @@ int Selector::exec(int startSelection) {
 					result = false;
 					break;
 				}
-
+				// ...fall through...
 			case InputManager::LEFT:
 				if (showDirectories) {
-					string::size_type p = dir.rfind("/", dir.size()-2);
-					if (p==string::npos || dir.length() < 2 || dir[0] != '/') {
+					string oldDir = dir;
+					dir = parentDir(dir);
+					if (dir == "/" && oldDir == "/") {
 						close = true;
 						result = false;
 					} else {
-						dir = dir.substr(0,p+1);
 						selected = 0;
 						firstElement = 0;
 						prepare(fl);
@@ -227,12 +230,14 @@ int Selector::exec(int startSelection) {
 	return result ? (int)selected : -1;
 }
 
-void Selector::prepare(FileLister& fl) {
-	fl.browse(dir);
+bool Selector::prepare(FileLister& fl) {
+	bool opened = fl.browse(dir);
 
 	screendir = dir;
 	if (!screendir.empty() && screendir[screendir.length() - 1] != '/') {
 		screendir += "/";
 	}
 	screendir += "previews/";
+
+	return opened;
 }

src/selector.h

@@ -35,7 +35,7 @@ private:
 	LinkApp& link;
 	std::string file, dir, screendir;
 
-	void prepare(FileLister& fl);
+	bool prepare(FileLister& fl);
 
 public:
 	Selector(GMenu2X *gmenu2x, LinkApp& link,

src/utilities.cpp

@@ -81,6 +81,13 @@ string readFileAsString(const char *filename) {
 	}
 }
 
+string parentDir(string const& dir) {
+	// Note that size() is unsigned, so for short strings the '- 2' wraps
+	// around and as a result the entire string is searched, which is fine.
+	auto p = dir.rfind('/', dir.size() - 2);
+	return p == string::npos ? "/" : dir.substr(0, p + 1);
+}
+
 bool fileExists(const string &file) {
 	fstream fin;
 	fin.open(file.c_str() ,ios::in);

src/utilities.h

@@ -52,6 +52,14 @@ std::string readFileAsString(const char *filename);
 std::string strreplace(std::string orig, const std::string &search, const std::string &replace);
 std::string cmdclean(std::string cmdline);
 
+/**
+ * Returns the parent directory of the given directory path, or "/" if there is
+ * no parent.
+ * This function does not check the file system: it is only string manipulation.
+ * @return The parent directory path, including a trailing '/'.
+ */
+std::string parentDir(std::string const& dir);
+
 inline std::string trimExtension(std::string const& filename) {
 	return filename.substr(0, filename.rfind('.'));
 }