Re: tiling window managers and alignment of frames

[Eli Zaretskii <eliz@gnu.org>]

> From: Gergely Riskó <gergely.risko@gmail.com>
> Date: Mon, 12 Feb 2024 04:17:18 +0100
> 
> Hi,
> 
> I'm using GNU Emacs 29.1 lucid (X toolkit).
> 
> In my setup, I only use fixed height fonts and all windows use the
> same font size, modeline has no extra line-space and internal frame
> border is set to 0.  Therefore if the height of a frame is divisible
> by (frame-char-height), the display is always guaranteed to be pixel
> perfect: no lines in any of the buffers with vertically half displayed
> lines, which looks nice.
> 
> Emacs has good configurability to keep this setup going: by default
> resize of frames is happening by (frame-char-height), and that
> behavior is quite nice, if I resize Emacs frames with a WM, the size
> of the frame keeps the divisibility by (frame-char-height).
> 
> Now, the problem is, that I'm using a tiling window manager (i3), and
> that ignores the size hints from Emacs when in tiling mode and just
> forces an arbitrary height.  And as a response to this, Emacs just
> assigns the extra pixels in the middle of the layout to one of the
> windows.
> 
> I'd like to have a variable (e.g. frame-resize-force-char-height) that
> tells Emacs that if all of the following is true:
> 
>   - frame-resize-force-char-height == t
>   - && frame-resize-pixelwise == nil
>   - && rem != 0
>     (where rem := (frame-pixel-height) % (frame-char-height))
> 
> then, the display engine should:
> 
>   - skip rem number of pixels right on top (or bottom) of the frame,
>   - and just use the background frame color for this vertical skip.
> 
> This is the behavior of xterm and urxvt (with the extra pixel lines
> being allocated to the bottom of the x11 window), and I'd like to have
> the same for my Lucid Emacs.
> 
> Is this possible or already implemented and did I just miss it?  I
> tried to do my research for a couple of hours, but didn't find it.
> Would it be difficult to add this to redisplay?  Is there any other
> workaround I could try to ensure that my windows never have halved
> displayed lines (until I keep my fonts all the same height in every
> window)?
> 
> Of course, my window manager could be intelligent enough to do this on
> the tiling side, but I don't think it would be easy to convince them,
> as they are pretty happy with the status of i3 as it is.
> 
> Any ideas?

Po Lu, any comments or suggestions?