Break out _lp_multiplexer() function and theme

The brackets for the default theme are colored when in a multiplexer, so
break that out of lp_activate() and put it in _lp_theme_activate().

liquidprompt

@@ -440,17 +440,13 @@ lp_activate() {
     # Use standard path symbols inside Midnight Commander
     [[ -n "${MC_SID-}" ]] && LP_ENABLE_SHORTEN_PATH=0
 
-    # If we are running in a terminal multiplexer, brackets are colored
-    if [[ "$TERM" == screen* || -n ${TMUX-} ]]; then
-        LP_BRACKET_OPEN="${LP_COLOR_IN_MULTIPLEXER}${LP_MARK_BRACKET_OPEN}${NO_COL}"
-        LP_BRACKET_CLOSE="${LP_COLOR_IN_MULTIPLEXER}${LP_MARK_BRACKET_CLOSE}${NO_COL}"
+    # If we are running in a terminal multiplexer, special title escapes
+    if _lp_multiplexer; then
         (( LP_ENABLE_TITLE = LP_ENABLE_TITLE && LP_ENABLE_SCREEN_TITLE ))
         LP_TITLE_OPEN=$'\Ek'
         # "\e\" but on bash \ must be escaped
         LP_TITLE_CLOSE=$'\E'"$_LP_BACKSLASH"
     else
-        LP_BRACKET_OPEN="${LP_MARK_BRACKET_OPEN}"
-        LP_BRACKET_CLOSE="${LP_MARK_BRACKET_CLOSE}"
         LP_TITLE_OPEN=$'\E]0;'
         LP_TITLE_CLOSE=$'\a'
     fi
@@ -782,6 +778,17 @@ _lp_chroot() {
     return 1
 }
 
+_lp_multiplexer() {
+    if [[ "$TERM" == screen* ]]; then
+        lp_mulitplexer=screen
+        return 0
+    elif [[ -n ${TMUX-} ]]; then
+        lp_mulitplexer=tmux
+        return 0
+    fi
+    return 1
+}
+
 # Put the hostname if not locally connected
 # color it in cyan within SSH, and a warning red if within telnet
 # else display the host without color
@@ -2192,6 +2199,15 @@ _lp_theme_activate() {
     _lp_hostname_color
     LP_HOST="$lp_hostname_color"
 
+    # If we are running in a terminal multiplexer, brackets are colored
+    if _lp_multiplexer; then
+        LP_BRACKET_OPEN="${LP_COLOR_IN_MULTIPLEXER}${LP_MARK_BRACKET_OPEN}${NO_COL}"
+        LP_BRACKET_CLOSE="${LP_COLOR_IN_MULTIPLEXER}${LP_MARK_BRACKET_CLOSE}${NO_COL}"
+    else
+        LP_BRACKET_OPEN="${LP_MARK_BRACKET_OPEN}"
+        LP_BRACKET_CLOSE="${LP_MARK_BRACKET_CLOSE}"
+    fi
+
     # Same as bash '\l', but inlined as a constant as the value will not change
     # during the shell's life
     LP_TTYN="$(basename -- "$(tty)" 2>/dev/null)"