You are too lazy to do the C-x C-+ + + +... - - - - ... + + - dance
all the time to see the FULL line in maximal font size?

You want a keystroke to see the whole buffer at once by changing the
font size?


fit-text-scale is an automation to set the scale so that the text
uses the maximal space to fit in the window.

Scale stands for the zoom of the font.

There are three functions:
- Choose the maximal text scale to still see the full line.
- Choose the maximal text scale to still see the full lines.
- Choose the maximal text scale to still see all lines of a buffer.

To get a feeling for the functions it's recommended to play around
with the commands.

- M-x fit-text-scale-max-font-size-fit-line
- M-x fit-text-scale-max-font-size-fit-lines
- M-x fit-text-scale-max-font-size-fit-buffer

If you want to use the functionality more conveniently it's
recommended to bind the commands to keys.  Find below a configuration
which extends the operations to act on region if a region is set.

The following code in an init file binds the functionality to keys.  Of
course you don't need to use these bindings.  You can choose your own
bindings.

#+begin_src emacs-lisp
(global-set-key
 (kbd "C-x C-&")
 (lambda (&optional arg)
   (interactive "P")
   (cond
    ((equal arg '(4)) (fit-text-scale-max-font-size-fit-line))
    ((equal arg '(16)) (fit-text-scale-max-font-size-fit-line-up-to-cursor))
    ((and (region-active-p) (< (region-beginning) (region-end)))
     (save-restriction
       (narrow-to-region (region-beginning) (region-end))
       (fit-text-scale-max-font-size-fit-lines)))
    (t (fit-text-scale-max-font-size-fit-lines)))))

(global-set-key
 (kbd "C-x C-*")
 (lambda (&optional arg)
   (interactive "P")
   (if (and (region-active-p) (< (region-beginning) (region-end)))
       (save-restriction
         (narrow-to-region (region-beginning) (region-end))
         (fit-text-scale-max-font-size-fit-buffer))
     (fit-text-scale-max-font-size-fit-buffer))))
#+end_src

With these settings there is

- C-u C-x C-&
  - Choose maximal text scale so that the current line still
    fits in the window.
- C-u C-u C-x C-&
  - Choose maximal text scale so that the current line up to the cursor
    still fits in the window. This can be useful with visual-line-mode.
- C-x C-&
  - Choose maximal text scale so that the longest line visible still
    fits in current window.
  - If region is active then only consider lines in the region.
- C-x C-*
  - Choose maximal text scale so that the vertical buffer content
    still fits into current window.
  - If region is active then only consider lines in the region.
- C-x C-0 (Already given with standard Emacs.  This is good old
  text-scale-adjust.)
  - Switch back to the default size when control about the sizes has
    been lost.
- Use e.g. C-x C-+ ==== + - and C-x C-- ----- - + for fine tuning.  (Also given.)
- C-g C-g C-g... (hit the keyboard hard!) if something, hrm, hangs.

There are some parameters to fine tune the functionality.  Check it out with

    M-x customize-group fit-text-scale


fit-text-scale is available on melpa.


Or use the good old style:

- Download fit-text-scale.el.

- Add the lines (with YOUR path to fit-text-scale.el)
to your init file.

#+begin_src emacs-lisp
(push "/PATH/TO/fit-text-scale" load-path)
(require 'fit-text-scale)
#+end_src