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riverguile/README.md
Leon Henrik Plickat e55ca945a0 add README.md
2023-11-25 16:22:16 +01:00

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# riverguile
Layout generator for the [river](https://github.com/riverwm/river) Wayland
server which uses [Guile Scheme](https://www.gnu.org/software/guile/) for
layouts. Its layout namespace is `riverguile`.
Uppon launch, riverguile tries to eval a scheme script and checks the following
paths for it in the given order:
* `layout.scm`
* `$XDG_CONFIG_HOME/river/layout.scm`
* `$HOME/.config/river/layout.scm`
* `/etc/riverguile/layout.scm`
This script must contain the definition of a function
`(layout-demand-handler view-count usable-width usable-height)` and may contain
any other code the user desires. The function must return a list containing
exactly as many lists as `view-count`. Each of those sublists must contains
exactly four numerical values for `x` and `y` position of the windows as well as
their width and height. Window positions and dimensions get applied to rivers
window list top to bottom.
Example of valid output:
```scheme
scheme@(guile-user)> (display (layout-demand-handler 3 1080 1920))
((0 0 594.0 1920) (594.0 0 486.0 960) (594.0 960 486.0 960))
```
Note that the numerical values do not need to be exact, riverguile takes care
of rounding and casting for you.
You can send riverguile layout-commands, which it will try to eval as scheme code.
```sh
riverctl map normal Super U send-layout-cmd riverguile "(define gaps 20)"
```
Here is an example `layout.scm` file replicating rivertiles behavior of having
a main window and a stack of windows aside:
```scheme
(define split 0.55)
(define (layout:rows n x y w h)
(letrec ((height (/ h n))
(rows (lambda (n)
(if (eq? n 0)
'()
(let ((Y (- (+ y h) (* n height))))
(append (list (list x Y w height))
(rows (- n 1))))))))
(rows n)))
(define (layout:split n x y w h)
(if (eq? n 1)
(list (list x y w h))
(letrec* ((left (* split w))
(right (- w left)))
(append (list (list x y left h))
(layout:rows (- n 1) (+ x left) y right h)))))
(define (layout-demand-handler view-count width height)
(layout:split view-count 0 0 width height))
```