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Programming in Emacs Lisp

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C.2.4 The Not Quite Final Version of print-Y-axis

The list constructed by the Y-axis-column function is passed to the print-Y-axis function, which inserts the list as a column.

 
(defun print-Y-axis (height full-Y-label-width)
  "Insert Y axis using HEIGHT and FULL-Y-LABEL-WIDTH.
Height must be the maximum height of the graph.
Full width is the width of the highest label element."
;; Value of height and full-Y-label-width
;; are passed by `print-graph'.
  (let ((start (point)))
    (insert-rectangle
     (Y-axis-column height full-Y-label-width))
    ;; Place point ready for inserting graph.
    (goto-char start)
    ;; Move point forward by value of full-Y-label-width
    (forward-char full-Y-label-width)))

The print-Y-axis uses the insert-rectangle function to insert the Y axis labels created by the Y-axis-column function. In addition, it places point at the correct position for printing the body of the graph.

You can test print-Y-axis:

  1. Install

     
    Y-axis-label-spacing
Y-axis-tic
Y-axis-element
Y-axis-column
print-Y-axis

  2. Copy the following expression:

     
    (print-Y-axis 12 5)

  3. Switch to the `*scratch*' buffer and place the cursor where you want the axis labels to start.

  4. Type M-: (eval-expression).

  5. Yank the graph-body-print expression into the minibuffer with C-y (yank).

  6. Press RET to evaluate the expression.

Emacs will print labels vertically, the top one being `10 - '. (The print-graph function will pass the value of height-of-top-line, which in this case would end up as 15.)


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