GNU screenのcaptionとhardstatusの整理

# Caption for each window
setenv a ""
setenv a "$a%?%F"     # if the window has the focus
setenv a "$a%{=d Wk}" #   set attribute = {dim, black(k) on bright Write(W)}
setenv a "$a%:"       # else
setenv a "$a%{=d Kk}" #   set attribute = {dim, black(k) on bright Black(K)}
setenv a "$a%?"       # end if
setenv a "$a%?%P"     # if copy/paste mode
setenv a "$a%{=d Bk}" #   set attribute = {dim, black(k) on bright Blue(B)}
setenv a "$a%?"       # end if
setenv a "$a%n"       # window number
setenv a "$a "        # space
setenv a "$a%L="      # Mark the position for the next truncation
setenv a "$a%h"       # window' hardstatus
setenv a "$a%L>"      # Truncate %L= ~ %L>, 'L' for > gives marks at the truncation point
setenv a "$a%="       # With the last %-0=, it makes right alignment for following lines
setenv a "$a%?%P"     # if copy/paste mode
setenv a "$a  *copy/paste*" # draw this sentence
setenv a "$a%?"       # end if
setenv a "$a%?%E"     # if copy/paste mode
setenv a "$a  ***command**" # draw this sentence
setenv a "$a%?"       # end if
setenv a "$a%-0="     # pad the string to the display's width. "-0" means
                      # start from the rightest side
                      # (e.g. 10=: 10% from left, 010, 10 characters from left
                      # (     -10=: 10% from right)
                      # With %L>, %= above, screen tries to truncates the part 
                      # in the left of "%L>"
caption always "$a"
unsetenv a

# hardstatus
setenv a ""
setenv a "$a%{= Kk}" # set attribute = {black(k) on bright Black(K)}
setenv a "$a%-w"     # windows' list up to the current window (shown as "%n %t")
setenv a "$a%40>"    # Mark here as a point to move when truncation
                     # Try to move this point to the 40% point
setenv a "$a%{= Wk}" # set attribute = {black(k) on bright Write(W)}
setenv a "$a%n"      # current window number
setenv a "$a "       # space
setenv a "$a%t"      # current window title
setenv a "$a%{-}"    # remove the set from the current attributes
setenv a "$a%+w"     # windows' list starting with the window after the current one (shown as "%n %t")
setenv a "$a%-0="    # pad the string to the display's width.
                     # About Truncation/Padding(=,<,>)
                     # http://aperiodic.net/screen/truncation_padding_escapes
hardstatus alwayslastline "$a"
unsetenv a