bug#74701: 31.0.50; vtable: cannot drag to resize columns when :use-header-line is nil

[Eli Zaretskii <eliz@gnu.org>]

Adam, any comments?

> Cc: Adam Porter <adam@alphapapa.net>
> From: Visuwesh <visuweshm@gmail.com>
> Date: Thu, 05 Dec 2024 20:01:41 +0530
> 
> When creating a vtable with :use-header-line nil (see below), dragging
> the column or the divider to resize the column is impossible because
> 
>   1. the function vtable--insert-header-line does not create the keymap
>      so that non-header-line mouse bindings actually resize the column
>   2. after inserting the header-line, vtable-insert completely
>      overwrites the keymap text-property which wipes out the keymap
>      setup by vtable--insert-header-line
> 
> To reproduce,
> 
>   1. emacs -Q
>   2. Evaluate the following sexp
> 
>       (with-current-buffer (get-buffer-create "asd")
>         (erase-buffer)
>         (require 'vtable)
>         (make-vtable
>          :use-header-line nil
>          :columns '("One" "Two")
>          :objects '((1 2) (3 4) (5 6)))
>         (pop-to-buffer (current-buffer)))    
>   3. Try to resize the column "Two" ("T" is shown here) by clicking on
>      "T" and dragging the pointer.
>   4. Witness no column resize.
>   5. Now, change :use-header-line to t and try to resize again.
>   6. Witness column resize.
> 
> The patch below fixes the issue on my end
> 
> 
> diff --git a/lisp/emacs-lisp/vtable.el b/lisp/emacs-lisp/vtable.el
> index c4f14d7b4b2..6f04eca3da8 100644
> --- a/lisp/emacs-lisp/vtable.el
> +++ b/lisp/emacs-lisp/vtable.el
> @@ -544,7 +544,7 @@ vtable-insert
>          ;; them).
>          (vtable--insert-header-line table widths spacer)
>          (add-text-properties start (point)
> -                             (list 'keymap vtable-header-line-map
> +                             (list ;;'keymap vtable-header-line-map
>                                     'rear-nonsticky t
>                                     'vtable table))
>          (setq start (point))))
> @@ -706,24 +706,34 @@ vtable--indicator
>  
>  (defun vtable--insert-header-line (table widths spacer)
>    ;; Insert the header directly into the buffer.
> -  (let ((start (point))
> -        (divider (vtable-divider table))
> -        (cmap (define-keymap
> -                "<header-line> <drag-mouse-1>" #'vtable--drag-resize-column
> -                "<header-line> <down-mouse-1>" #'ignore))
> -        (dmap (define-keymap
> -                "<header-line> <drag-mouse-1>"
> -                (lambda (e)
> -                  (interactive "e")
> -                  (vtable--drag-resize-column e t))
> -                "<header-line> <down-mouse-1>" #'ignore)))
> +  (let* ((start (point))
> +         (divider (vtable-divider table))
> +         (rev-resize-fun (lambda (e)
> +                           (interactive "e")
> +                           (vtable--drag-resize-column e t)))
> +         (cmap (define-keymap
> +                 :parent vtable-header-line-map
> +                 "<header-line> <drag-mouse-1>" #'vtable--drag-resize-column
> +                 "<header-line> <down-mouse-1>" #'ignore
> +                 "<drag-mouse-1>" #'vtable--drag-resize-column
> +                 "<down-mouse-1>" #'ignore))
> +         (dmap (define-keymap
> +                 :parent vtable-header-line-map
> +                 "<header-line> <drag-mouse-1>" rev-resize-fun
> +                 "<header-line> <down-mouse-1>" #'ignore
> +                 "<drag-mouse-1>" rev-resize-fun
> +                 "<down-mouse-1>" #'ignore)))
>      (seq-do-indexed
>       (lambda (column index)
>         (let* ((name (propertize
>                       (vtable-column-name column)
>                       'face (list 'header-line (vtable-face table))
>                       'mouse-face 'header-line-highlight
> -                     'keymap cmap))
> +                     ;; Reverse resizing is more intuitive for the first
> +                     ;; column.
> +                     'keymap (if (= index 0)
> +                                 dmap
> +                               cmap)))
>                (start (point))
>                (indicator (vtable--indicator table index))
>                (indicator-width (string-pixel-width indicator))
> 
> 
> I also took the liberty to make one other change:
> 
>     I use DMAP instead of CMAP for the first column.  Without this
>     change, dragging the first column does nothing.  With this change,
>     dragging the first column to the left will increase its size.  I
>     think this behaviour is more intuitive than doing nothing.
> 
> In GNU Emacs 31.0.50 (build 25, x86_64-pc-linux-gnu, X toolkit, cairo
>  version 1.18.2, Xaw scroll bars) of 2024-11-10 built on astatine
> Repository revision: 1704fa4fb4164a15c7e258b922dbba190811d92d
> Repository branch: master
> Windowing system distributor 'The X.Org Foundation', version 11.0.12101014
> System Description: Debian GNU/Linux trixie/sid
> 
> Configured using:
>  'configure --with-sound=alsa --with-x-toolkit=lucid --without-xaw3d
>  --without-gconf --without-libsystemd --with-cairo CFLAGS=-g3'
> Configured features:
> ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
> LCMS2 LIBOTF LIBSELINUX LIBXML2 MODULES NOTIFY INOTIFY PDUMPER PNG RSVG
> SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS WEBP X11 XDBE XIM
> XINPUT2 XPM LUCID ZLIB
> Important settings:
>   value of $LC_MONETARY: ta_IN.UTF-8
>   value of $LC_NUMERIC: ta_IN.UTF-8
>   value of $LANG: en_GB.UTF-8
>   locale-coding-system: utf-8-unix