[code](fff) Slight cleanup and documentation

fff

@@ -297,6 +297,7 @@ get_icon() {
 
     # Icon for files whose names have an extension
     [[ "$2" == *"."* ]] && {
+        # Special files
         case "$2" in
             'cmakelists.txt'                   |\
             'Makefile.ac'                      |\
@@ -338,6 +339,7 @@ get_icon() {
             'react.jsx'                        ) printf -- ''; return ;;
         esac
 
+        # extension
         case "$3" in
             '7z'  | 'apk'   |\
             'bz2' | 'cab'   |\
@@ -626,7 +628,7 @@ print_line() {
     fi
 
     # If the list item is under the cursor.
-    (($1 == scroll)) &&
+    (("$1" == scroll)) &&
         format+="\\e[1;3${FFF_COL4:-6};7m"
 
     # If the list item is marked for operation.
@@ -637,9 +639,9 @@ print_line() {
 
     # Escape the directory string.
     # Remove all non-printable characters.
-    file_name=${file_name//[^[:print:]]/^[}
+    file_name="${file_name//[^[:print:]]/^[}"
 
-    (( ${FFF_FILE_ICON:=0} == 1 )) && \
+    (( "${FFF_FILE_ICON:=0}" == 1 )) && \
         icon="$(get_icon "${list[$1]}" "$file_name" "$file_ext") "
 
     printf '\r%b%s\e[m\r' \
@@ -1451,10 +1453,10 @@ main() {
     ((BASH_VERSINFO[0] > 3)) &&
         read_flags=(-t 0.05)
 
-    ((${FFF_LS_COLORS:=1} == 1)) &&
+    (("${FFF_LS_COLORS:=1}" == 1)) &&
         get_ls_colors
 
-    ((${FFF_HIDDEN:=0} == 1)) &&
+    (("${FFF_HIDDEN:=0}"== 1)) &&
         shopt -s dotglob
 
     # Create the trash and cache directory if they don't exist.