new utility function for BLI_storage.h - BLI_is_dir

currently unsupported on windows.

should fix this too [#19656] N-Panel in filebrowser not working
though typing in invalid names then becomes possible

source/blender/blenlib/BLI_storage.h

@@ -66,6 +66,9 @@ int    BLI_exist(char *name);
 	 * @param name The name of the file to read.
 	 * @retval A list of strings representing the file lines.
 	 */
+
+int BLI_is_dir(char *file);
+
 struct LinkNode *BLI_read_file_as_lines(char *name);
 
 	/**

source/blender/blenlib/intern/storage.c

@@ -468,6 +468,15 @@ int BLI_exist(char *name)
 	return(st.st_mode);
 }
 
+/* would be better in fileops.c except that it needs stat.h so add here */
+int BLI_is_dir(char *file) {
+#ifdef WIN32
+	return 1; /* XXX - TODO */
+#else
+	return S_ISDIR(BLI_exist(file));
+#endif
+}
+
 LinkNode *BLI_read_file_as_lines(char *name)
 {
 	FILE *fp= fopen(name, "r");

source/blender/editors/space_file/filesel.c

@@ -388,7 +388,7 @@ void file_change_dir(struct SpaceFile *sfile, int checkdir)
 {
 	if (sfile->params) {
 
-		if(checkdir && S_ISDIR(BLI_exists(sfile->params->dir)) == 0) {
+		if(checkdir && BLI_is_dir(sfile->params->dir)==0) {
 			BLI_strncpy(sfile->params->dir, filelist_dir(sfile->files), sizeof(sfile->params->dir));
 			/* could return but just refresh the current dir */
 		}