Re: Better handling of window margins

[martin rudalics]

> For the first issue, IMO it isn't enough to specify just one value,
> the required margin width.  You need also to specify the width of the
> stuff, if any, that is displayed in the margin.  (This will have to be
> specified in pixels, because you can display images and pixel-granular
> stretches of white space in the margins.)  For example, linum-mode
> will specify a margin width of N columns, and display width of the
> same N columns in pixels.

How would this work with scaled text?

> By contrast, modes such as writeroom-mode
> will specify a margin width of M columns and display width of zero.
>
> So we need to maintain, for each of the 2 margins, a list of elements
> of the form:
>
>     (SYMBOL MARGIN-WIDTH DISPLAY-WIDTH)
>
> where SYMBOL is a unique symbol used to identify the request that came
> from a specific feature/mode.  We should provide a function to return
> this list, or maybe make it the value of a local public variable.  We
> should also have a way for a feature to update its request.

This probably has to be a window parameter because at least the
margin-width may differ according to the window the buffer is displayed in.

> Now regarding the split-window issue.  I believe we shouldn't try to
> second-guess how to split windows in these cases.  Instead, we should
> place the burden of doing TRT on the modes.  Specifically:
>
>   . for splitting the window with "C-x 2" and "C-x 3", the mode could
>     simply invoke the correct splitting function itself

When two modes simultaneously use the margins, which splitting function
would be chosen?

>   . for splitting the window as result of some command calling
>     display-buffer, we could expect the modes to customize the
>     display-buffer-* variables to control how the window is split (if
>     there are currently no features/variables to that effect, we should
>     add them)

When two modes simultaneously use the margins, which buffer display
function would be chosen?

And how would we handle functions like ‘set-window-fringes’ or
‘set-frame-width’?

martin