v0.0.3: layout engine — pure CL Flexbox constraint solver and push

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Hermes
2026-05-11 13:12:35 +00:00
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;;; layout — Pure CL Flexbox layout engine
(defpackage :cl-tui.layout
(:use :cl)
(:export
#:layout-node #:make-layout-node
#:layout-node-add-child #:layout-node-remove-child
#:layout-node-children
#:layout-node-x #:layout-node-y
#:layout-node-width #:layout-node-height
#:layout-node-direction
#:compute-layout
#:vbox #:hbox #:spacer
;; For tests
#:layout-node-parent #:layout-node-fixed-width
#:layout-node-fixed-height #:normalize-box
#:box-edge))
(in-package :cl-tui.layout)
(defclass layout-node ()
((parent :initform nil :accessor layout-node-parent)
(children :initform nil :accessor layout-node-children)
(x :initform 0 :accessor layout-node-x)
(y :initform 0 :accessor layout-node-y)
(width :initform 0 :accessor layout-node-width)
(height :initform 0 :accessor layout-node-height)
(direction :initform :column :initarg :direction :accessor layout-node-direction)
(grow :initform 0 :initarg :grow :accessor layout-node-grow)
(shrink :initform 1 :initarg :shrink :accessor layout-node-shrink)
(padding :initform '(:top 0 :right 0 :bottom 0 :left 0) :initarg :padding :accessor layout-node-padding)
(margin :initform '(:top 0 :right 0 :bottom 0 :left 0) :initarg :margin :accessor layout-node-margin)
(gap :initform 0 :initarg :gap :accessor layout-node-gap)
(position-type :initform :relative :initarg :position-type :accessor layout-node-position-type)
(position-offset :initform nil :initarg :position-offset :accessor layout-node-position-offset)
(fixed-width :initform nil :initarg :width :accessor layout-node-fixed-width)
(fixed-height :initform nil :initarg :height :accessor layout-node-fixed-height)))
(defun make-layout-node (&key direction grow shrink padding margin gap
position-type position-offset width height)
(make-instance 'layout-node
:direction (or direction :column)
:grow (or grow 0) :shrink (or shrink 1)
:padding (normalize-box padding) :margin (normalize-box margin)
:gap gap
:position-type (or position-type :relative)
:position-offset position-offset
:width width :height height))
(defun normalize-box (spec)
(cond ((null spec) '(:top 0 :right 0 :bottom 0 :left 0))
((numberp spec) `(:top ,spec :right ,spec :bottom ,spec :left ,spec))
((getf spec :top) spec)
(t '(:top 0 :right 0 :bottom 0 :left 0))))
(defun box-edge (box edge)
(or (getf box edge) 0))
(defun layout-node-add-child (parent child)
(setf (layout-node-parent child) parent)
(push child (layout-node-children parent))
child)
(defun layout-node-remove-child (parent child)
(setf (layout-node-parent child) nil)
(setf (layout-node-children parent)
(delete child (layout-node-children parent)))
child)
;; ── Solver ─────────────────────────────────────────────────────
(defun distribute-sizes (children avail gap)
"Compute child sizes given available space and gap."
(let* ((n (length children))
(default-size (if (zerop n) 0 (round avail n)))
(gap-total (* gap (max 0 (1- n))))
(sizes (mapcar (lambda (c)
(or (if (eql (layout-node-direction c) :row)
(layout-node-fixed-width c)
(layout-node-fixed-height c))
default-size))
children))
(total (reduce #'+ sizes))
(remaining (- total (- avail gap-total)))
(grow-total (reduce #'+ (mapcar #'layout-node-grow children)))
(shrink-total (reduce #'+ (mapcar #'layout-node-shrink children))))
(mapcar (lambda (c sz)
(let ((g (layout-node-grow c))
(s (layout-node-shrink c))
(size sz))
(when (and (plusp remaining) (plusp grow-total))
(incf size (round (* remaining (/ g grow-total)))))
(when (and (minusp remaining) (plusp shrink-total))
(decf size (round (* (abs remaining) (/ s shrink-total)))))
(max 1 size)))
children sizes)))
(defun compute-layout (root available-width available-height)
(labels ((place-children (node x y max-w max-h)
(let* ((children (reverse (layout-node-children node)))
(is-row (eql (layout-node-direction node) :row))
(pl (box-edge (layout-node-padding node) :left))
(pt (box-edge (layout-node-padding node) :top))
(pr (box-edge (layout-node-padding node) :right))
(pb (box-edge (layout-node-padding node) :bottom))
(cw (max 0 (- max-w pl pr)))
(ch (max 0 (- max-h pt pb)))
(gap (layout-node-gap node))
(sizes (distribute-sizes children (if is-row cw ch) gap)))
(setf (layout-node-x node) (+ x pl)
(layout-node-y node) (+ y pt))
(loop with pos = 0
for child in children
for size in sizes
do (if is-row
(setf (layout-node-width child) size
(layout-node-x child) (+ x pl pos)
(layout-node-height child) ch
(layout-node-y child) (+ y pt))
(setf (layout-node-height child) size
(layout-node-y child) (+ y pt pos)
(layout-node-width child) cw
(layout-node-x child) (+ x pl)))
(place-children child (layout-node-x child) (layout-node-y child)
(if is-row size cw) (if is-row ch size))
(incf pos (+ size gap))))
(let ((last (car (last children))))
(if is-row
(setf (layout-node-width node)
(or (layout-node-fixed-width node)
(if last (+ (layout-node-x node) (layout-node-width last) (box-edge (layout-node-padding node) :right)) max-w))
(layout-node-height node) max-h)
(setf (layout-node-height node)
(or (layout-node-fixed-height node)
(if last (+ (layout-node-y node) (layout-node-height last) (box-edge (layout-node-padding node) :bottom)) max-h))
(layout-node-width node) max-w)))))
(place-children root 0 0 available-width available-height)
root))
;; ── Macros ─────────────────────────────────────────────────────
(defmacro vbox ((&key grow shrink padding margin gap width height) &body children)
(let ((n (gensym)))
`(let ((,n (make-layout-node :direction :column
,@(when grow `(:grow ,grow))
,@(when shrink `(:shrink ,shrink))
,@(when padding `(:padding ,padding))
,@(when margin `(:margin ,margin))
,@(when gap `(:gap ,gap))
,@(when width `(:width ,width))
,@(when height `(:height ,height)))))
,@(loop for c in children collect `(layout-node-add-child ,n ,c))
,n)))
(defmacro hbox ((&key grow shrink padding margin gap width height) &body children)
(let ((n (gensym)))
`(let ((,n (make-layout-node :direction :row
,@(when grow `(:grow ,grow))
,@(when shrink `(:shrink ,shrink))
,@(when padding `(:padding ,padding))
,@(when margin `(:margin ,margin))
,@(when gap `(:gap ,gap))
,@(when width `(:width ,width))
,@(when height `(:height ,height)))))
,@(loop for c in children collect `(layout-node-add-child ,n ,c))
,n)))
(defmacro spacer (&key grow)
`(make-layout-node :grow ,(or grow 1)))

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(defpackage :cl-tui-layout-test
(:use :cl :fiveam :cl-tui.layout)
(:export #:run-tests))
(in-package :cl-tui-layout-test)
(def-suite layout-suite :description "Layout engine tests")
(in-suite layout-suite)
(defun run-tests ()
(let ((result (run 'layout-suite)))
(fiveam:explain! result)
(uiop:quit 0)))
(test make-layout-node-defaults
(let ((n (make-layout-node)))
(is (typep n 'layout-node))
(is (eql (layout-node-direction n) :column))))
(test make-layout-node-row
(let ((n (make-layout-node :direction :row)))
(is (eql (layout-node-direction n) :row))))
(test add-child-sets-parent
(let ((parent (make-layout-node)) (child (make-layout-node)))
(layout-node-add-child parent child)
(is (eql (layout-node-parent child) parent))
(is (= (length (layout-node-children parent)) 1))))
(test remove-child-clears-parent
(let ((parent (make-layout-node)) (child (make-layout-node)))
(layout-node-add-child parent child)
(layout-node-remove-child parent child)
(is (null (layout-node-parent child)))
(is (= (length (layout-node-children parent)) 0))))
(test column-two-children-vertical
(let* ((root (make-layout-node :direction :column))
(c1 (make-layout-node :height 3))
(c2 (make-layout-node :height 5)))
(layout-node-add-child root c1) (layout-node-add-child root c2)
(compute-layout root 20 20)
(is (= (layout-node-y c1) 0)) (is (= (layout-node-height c1) 3))
(is (= (layout-node-y c2) 3)) (is (= (layout-node-height c2) 5))))
(test row-two-children-horizontal
(let* ((root (make-layout-node :direction :row))
(c1 (make-layout-node :width 10))
(c2 (make-layout-node :width 5)))
(layout-node-add-child root c1) (layout-node-add-child root c2)
(compute-layout root 20 10)
(is (= (layout-node-x c1) 0)) (is (= (layout-node-width c1) 10))
(is (= (layout-node-x c2) 10)) (is (= (layout-node-width c2) 5))))
(test flex-grow-distributes-space
(let* ((root (make-layout-node :direction :row :width 20))
(c1 (make-layout-node :width 4 :grow 1))
(c2 (make-layout-node :width 4 :grow 2)))
(layout-node-add-child root c1) (layout-node-add-child root c2)
(compute-layout root 20 10)
(is (= (layout-node-width c1) 8)) (is (= (layout-node-width c2) 12))))
(test flex-grow-single-child
(let* ((root (make-layout-node :direction :row :width 20))
(c (make-layout-node :width 5 :grow 1)))
(layout-node-add-child root c)
(compute-layout root 20 10)
(is (= (layout-node-width c) 20))))
(test flex-shrink-reduces-overflow
(let* ((root (make-layout-node :direction :row :width 10))
(c1 (make-layout-node :width 8 :shrink 1))
(c2 (make-layout-node :width 8 :shrink 1)))
(layout-node-add-child root c1) (layout-node-add-child root c2)
(compute-layout root 10 10)
(is (= (layout-node-width c1) 5)) (is (= (layout-node-width c2) 5))))
(test padding-reduces-content-area
(let* ((root (make-layout-node :direction :column :padding '(:top 1 :left 1 :bottom 1 :right 1)))
(c (make-layout-node :height 3)))
(layout-node-add-child root c)
(compute-layout root 20 10)
(is (= (layout-node-x c) 1)) (is (= (layout-node-y c) 1))
(is (= (layout-node-height c) 3))))
(test gap-between-children
(let* ((root (make-layout-node :direction :column :gap 2))
(c1 (make-layout-node :height 3))
(c2 (make-layout-node :height 3)))
(layout-node-add-child root c1) (layout-node-add-child root c2)
(compute-layout root 20 20)
(is (= (layout-node-y c1) 0)) (is (= (layout-node-y c2) 5))))
(test vbox-macro
(let ((r (vbox () (make-layout-node :height 3) (make-layout-node :height 5))))
(compute-layout r 20 20)
(is (= (length (layout-node-children r)) 2))
(is (= (layout-node-y (elt (layout-node-children r) 1)) 3))))
(test hbox-macro
(let ((r (hbox () (make-layout-node :width 5) (make-layout-node :width 3))))
(compute-layout r 20 10)
(is (= (length (layout-node-children r)) 2))
(is (= (layout-node-x (elt (layout-node-children r) 1)) 5))))
(test spacer-takes-grow
(let ((r (hbox (:width 20) (make-layout-node :width 5) (spacer :grow 1) (make-layout-node :width 5))))
(compute-layout r 20 10)
(let ((c (layout-node-children r)))
(is (= (layout-node-x (elt c 2)) 15)) (is (= (layout-node-width (elt c 1)) 10)))))
(test nested-vbox-in-hbox
(let* ((sidebar (vbox (:width 5 :height 10) (make-layout-node :height 3) (make-layout-node :height 7)))
(main (vbox (:grow 1 :height 10) (make-layout-node :height 2) (make-layout-node :grow 1)))
(r (hbox (:width 30 :height 10) sidebar main)))
(compute-layout r 30 10)
(is (= (layout-node-width sidebar) 5))
(is (>= (layout-node-width main) 20))
(let ((sc (layout-node-children sidebar)))
(is (= (layout-node-y (elt sc 0)) 0))
(is (= (layout-node-y (elt sc 1)) 3)))))