Re: The future of Follow Mode - a proposal.

[Anders Lindgren]

IMO, moving the code to C will solve only the marginal aspects of
this.  The main problem -- the fact that the current display engine
doesn't support windows of unequal width -- cannot be solved without
deep changes.  We need to at least design these changes first, so that
we have a clear idea how to solve these issues.  FWIW, I thought about
this for a while, and didn't see any easy way of doing it.

If we abandon the design goal of supporting windows of unequal width,
the problem becomes much easier.

Windows of unequal width is something that we need to live with, at least if follow-mode is something that a user can enable without affecting the layout of a frame, like today.

Anyway, wouldn't it be possible for the display engine to do the layout of the leftmost window (of a follow mode window group) using the normal system for finding a suitable start location on even line boundaries. The rest of the windows in the window group could then use the end position of the previous window.

In fact, I think it could be supported today from lisp if only it was possible to disable the part of the display engine that ensures that the window start position is an even multiple of the window width, on a window-by-window basis. In the case of follow-mode, the leftmost window should keep it enabled, whereas the rest should disable this feature.

(The only thing that wouldn't work is if a multi-width character (like control-l "^L") is partially visible. It will continue to work like today, with "^" visible at the end of one window and "^L" at the start of the next.)

    -- Anders