Info Catalog elisp: Mode Line Format elisp: Mode Line Data

elisp: Mode Line Basics

 
 22.4.1 Mode Line Basics
 -----------------------
 
 The contents of each mode line are specified by the buffer-local
 variable ‘mode-line-format’ (Mode Line Top).  This variable
 holds a “mode line construct”: a template that controls what is
 displayed on the buffer’s mode line.  The value of ‘header-line-format’
 specifies the buffer’s header line in the same way.  All windows for the
 same buffer use the same ‘mode-line-format’ and ‘header-line-format’.
 
    For efficiency, Emacs does not continuously recompute each window’s
 mode line and header line.  It does so when circumstances appear to call
 for it—for instance, if you change the window configuration, switch
 buffers, narrow or widen the buffer, scroll, or modify the buffer.  If
 you alter any of the variables referenced by ‘mode-line-format’ or
 ‘header-line-format’ (Mode Line Variables), or any other data
 structures that affect how text is displayed (Display), you
 should use the function ‘force-mode-line-update’ to update the display.
 
  -- Function: force-mode-line-update &optional all
      This function forces Emacs to update the current buffer’s mode line
      and header line, based on the latest values of all relevant
      variables, during its next redisplay cycle.  If the optional
      argument ALL is non-‘nil’, it forces an update for all mode lines
      and header lines.
 
      This function also forces an update of the menu bar and frame
      title.
 
    The selected window’s mode line is usually displayed in a different
 color using the face ‘mode-line’.  Other windows’ mode lines appear in
 the face ‘mode-line-inactive’ instead.  Faces.
 

Info Catalog elisp: Mode Line Format elisp: Mode Line Data