bug#17788: 24.3; ruler-mode: column indicators "hop" left if you drag them diagonally

[Lars Ingebrigtsen]

Andrea Rossetti <andrea.rossetti@gmail.com> writes:

>  - start emacs -Q
>  - M-x ruler-mode RET
>  - click S-<mouse-1> on the column 10 of the ruler, this will set a left
>    margin
>  - you will see the ruler has two column indicators in red colour:
>    "#" for comment column, and "pilcrow" symbol for paragraph fill indicator
>  - click and hold down mouse-2 (= center mouse button) on the red "#" 
> indicator
>  - drag the indicator horizontally; indicator will follow the mouse as 
> expected
>  - continue dragging slightly diagonally (for example in West-South-West
>    direction); as soon as you drag the mouse out of the grey ruler area,
>    you will see that the indicator "hops" left of about 10 columns

I can confirm that this bug is still present in Emacs 28.  (Well, it
behaves slightly differently, but the "jump" is still there.)

Andrea Rossetti <andrea.rossetti@gmail.com> writes:

>   The new tentative patch is attached here below:

This unfortunately got no followup at the time, and in the years since
this, ruler-mode has changed substantially, and the patch no longer
applies.

Would it be possible for you to respin the patch, and we can actually
get it applied this time?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no