> 1. Lose the *...* earmuffs.  Elisp doesn't embrace that CL convention for
defvars.

I wonder, is it because Emacs had only dynamic binding? Maybe now the
"*..*" can be helpful to distinguish dynamic vars from lexical.

> 2. The var's doc should say what it means by "skip".  Apparently it means
(only) that function `apply-on-rectangle' doesn't apply
its FUNCTION arg to empty lines.  I think it's important to say that the
var affects (only) that function's behavior.

I think the application of FUNCTION is the main part of
`apply-on-rectangle', so it is more or less obvious.
And you can easily see the effect in GUI, when using `rectangle-mark-mode'
(C-x SPC).

I'm not quite sure how to name the var.


*What it does:*

For example you have a buffer "env.sh" with content:




*"FOO=1BAR=2"*

Now if you do
`M-<'          beginning-of-buffer
`C-x SPC'      rectangle-mark-mode
`C-n'          next-line
`C-n'          next-line
`C-t'          string-rectangle
`export RET'

With standard rect.el you will get:




*"export FOO=1export export BAR=2"*

With patched version and `rectangle-select-skip-line'(new name of var) set
to `t':




*"export FOO=1export BAR=2"*

*New version of patch:*

--- rect-orig.el 2023-01-31 17:25:08.498658466 +0300
+++ rect-patched.el 2023-02-02 20:21:11.041198925 +0300
@@ -144,11 +144,18 @@

 ;;; Rectangle operations.

+(defvar rectangle-select-skip-line nil
+  "Control the `apply-on-rectangle' execution.
+`nil' -- apply action to selected lines, `t' -- skip empty lines,
+`function' -- skip line if it return non-`nil'.
+The function get all arguments of `apply-on-rectangle' as input.")
+
 (defun apply-on-rectangle (function start end &rest args)
   "Call FUNCTION for each line of rectangle with corners at START, END.
 FUNCTION is called with two arguments: the start and end columns of the
 rectangle, plus ARGS extra arguments.  Point is at the beginning of line
when
 the function is called.
+The `rectangle-select-skip-line' variable allow to skip lines.
 The final point after the last operation will be returned."
   (save-excursion
     (let* ((cols (rectangle--pos-cols start end))
@@ -166,7 +173,14 @@
       (goto-char startpt)
       (while
           (progn
-            (apply function startcol endcol args)
+            (when (cond
+                   ((null rectangle-select-skip-line)
+                    t)
+                   ((functionp rectangle-select-skip-line)
+                    (apply rectangle-select-skip-line function start end
args))
+                   (t
+                    (not (string-match-p "\\`\\s-*$" (thing-at-point
'line)))))
+              (apply function startcol endcol args))
             (setq final-point (point))
             (and (zerop (forward-line 1)) (bolp)
                  (<= (point) endpt))))


On Tue, 31 Jan 2023 at 19:18, Drew Adams <drew.adams@oracle.com> wrote:

>
>