csv-mode: header does not align when line numbers are displayed

csv-mode: header does not align when line numbers are displayed

[Joost]

Hi list,

Not sure if this should be reported as a bug or not; let me know if it should.

`csv-mode` has the option to display a header line so you can make column names permanently visible, which is a very nice option. However, when `display-line-numbers-mode` is active, the column names do not line up with the actual columns, because the header line does not take into account the space taken up by the line numbers.

The following patch seems to be a quick fix:

```
diff --git a/csv-mode.el b/csv-mode.el
index 10ce166052..33118aa2e8 100644
--- a/csv-mode.el
+++ b/csv-mode.el
@@ -1382,6 +1382,10 @@ If there is already a header line, then unset the header line."
       (move-to-column (or csv--header-hscroll 0))
       (let ((str (replace-regexp-in-string
                  "%" "%%" (buffer-substring (point) (line-end-position))))
+            (line-number-width (if (and (bound-and-true-p display-line-numbers-mode)
+                                        display-line-numbers-width)
+                                   (+ 2 display-line-numbers-width)
+                                 0))
             (i 0))
         (while (and i (< i (length str)))
           (let ((prop (get-text-property i 'display str)))
@@ -1392,13 +1396,13 @@ If there is already a header line, then unset the header line."
                         (newprop
                          `(space :align-to
                                  ,(if (numberp x)
-                                      (- x (or csv--header-hscroll 0))
-                                    `(- ,x csv--header-hscroll)))))
+                                      (+ line-number-width (- x (or csv--header-hscroll 0)))
+                                    `(+ line-number-width (- ,x csv--header-hscroll))))))
                    (put-text-property i (or nexti (length str))
                                       'display newprop str)
                    (setq i nexti))))
           (setq i (next-single-property-change i 'display str)))
-        (concat (propertize " " 'display '((space :align-to 0))) str)))))
+        (concat (propertize " " 'display `((space :align-to ,line-number-width))) str)))))
 
 ;;; Auto-alignment
 
```

Though it doesn't automatically adjust the header line when `display-line-numbers-mode` is toggled or if `display-line-number-width` changes, so it's probably not the ideal solution.

Thanks,

-- 
Joost Kremers
Life has its moments

Re: csv-mode: header does not align when line numbers are displayed

[Eli Zaretskii]

> Date: Fri, 29 Apr 2022 09:47:08 +0200
> From: Joost <joostkremers@fastmail.fm>
> 
> Not sure if this should be reported as a bug or not; let me know if it should.

The bug tracker is not just for bugs, it is also for features.  So
yes, please post such suggestions via "M-x report-emacs-bug".

> `csv-mode` has the option to display a header line so you can make column names permanently visible, which is a very nice option. However, when `display-line-numbers-mode` is active, the column names do not line up with the actual columns, because the header line does not take into account the space taken up by the line numbers.
> 
> The following patch seems to be a quick fix:

Thanks.

> Though it doesn't automatically adjust the header line when `display-line-numbers-mode` is toggled or if `display-line-number-width` changes, so it's probably not the ideal solution.

Indeed.  I think tabulated-list.el shows how to cause the adjustment
when the variable is toggled.  Can you use those ideas to submit a
better solution?

Re: csv-mode: header does not align when line numbers are displayed

[Joost Kremers]

On Fri, Apr 29 2022, Eli Zaretskii wrote:
>> Date: Fri, 29 Apr 2022 09:47:08 +0200
>> From: Joost <joostkremers@fastmail.fm>
>> Though it doesn't automatically adjust the header line when
>> `display-line-numbers-mode` is toggled or if `display-line-number-width`
>> changes, so it's probably not the ideal solution.
>
> Indeed.  I think tabulated-list.el shows how to cause the adjustment
> when the variable is toggled.  Can you use those ideas to submit a
> better solution?

Not sure. It's difficult to estimate how much time I'd need (not being familiar
with the code for tabulated-list-mode) and when I'd have that time. I sent a bug
report to make sure it's not forgotten. If I don't come up with a solution,
perhaps someone else with a little time on their hands will.

-- 
Joost Kremers
Life has its moments