v0.0.3: layout engine — pure CL Flexbox constraint solver and push
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Hermes
169
layout/layout.lisp
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169
layout/layout.lisp
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;;; layout — Pure CL Flexbox layout engine
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(defpackage :cl-tui.layout
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(:use :cl)
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(:export
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#:layout-node #:make-layout-node
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#:layout-node-add-child #:layout-node-remove-child
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#:layout-node-children
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#:layout-node-x #:layout-node-y
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#:layout-node-width #:layout-node-height
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#:layout-node-direction
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#:compute-layout
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#:vbox #:hbox #:spacer
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;; For tests
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#:layout-node-parent #:layout-node-fixed-width
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#:layout-node-fixed-height #:normalize-box
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#:box-edge))
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(in-package :cl-tui.layout)
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(defclass layout-node ()
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((parent :initform nil :accessor layout-node-parent)
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(children :initform nil :accessor layout-node-children)
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(x :initform 0 :accessor layout-node-x)
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(y :initform 0 :accessor layout-node-y)
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(width :initform 0 :accessor layout-node-width)
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(height :initform 0 :accessor layout-node-height)
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(direction :initform :column :initarg :direction :accessor layout-node-direction)
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(grow :initform 0 :initarg :grow :accessor layout-node-grow)
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(shrink :initform 1 :initarg :shrink :accessor layout-node-shrink)
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(padding :initform '(:top 0 :right 0 :bottom 0 :left 0) :initarg :padding :accessor layout-node-padding)
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(margin :initform '(:top 0 :right 0 :bottom 0 :left 0) :initarg :margin :accessor layout-node-margin)
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(gap :initform 0 :initarg :gap :accessor layout-node-gap)
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(position-type :initform :relative :initarg :position-type :accessor layout-node-position-type)
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(position-offset :initform nil :initarg :position-offset :accessor layout-node-position-offset)
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(fixed-width :initform nil :initarg :width :accessor layout-node-fixed-width)
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(fixed-height :initform nil :initarg :height :accessor layout-node-fixed-height)))
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(defun make-layout-node (&key direction grow shrink padding margin gap
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position-type position-offset width height)
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(make-instance 'layout-node
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:direction (or direction :column)
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:grow (or grow 0) :shrink (or shrink 1)
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:padding (normalize-box padding) :margin (normalize-box margin)
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:gap gap
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:position-type (or position-type :relative)
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:position-offset position-offset
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:width width :height height))
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(defun normalize-box (spec)
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(cond ((null spec) '(:top 0 :right 0 :bottom 0 :left 0))
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((numberp spec) `(:top ,spec :right ,spec :bottom ,spec :left ,spec))
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((getf spec :top) spec)
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(t '(:top 0 :right 0 :bottom 0 :left 0))))
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(defun box-edge (box edge)
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(or (getf box edge) 0))
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(defun layout-node-add-child (parent child)
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(setf (layout-node-parent child) parent)
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(push child (layout-node-children parent))
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child)
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(defun layout-node-remove-child (parent child)
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(setf (layout-node-parent child) nil)
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(setf (layout-node-children parent)
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(delete child (layout-node-children parent)))
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child)
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;; ── Solver ─────────────────────────────────────────────────────
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(defun distribute-sizes (children avail gap)
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"Compute child sizes given available space and gap."
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(let* ((n (length children))
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(default-size (if (zerop n) 0 (round avail n)))
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(gap-total (* gap (max 0 (1- n))))
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(sizes (mapcar (lambda (c)
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(or (if (eql (layout-node-direction c) :row)
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(layout-node-fixed-width c)
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(layout-node-fixed-height c))
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default-size))
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children))
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(total (reduce #'+ sizes))
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(remaining (- total (- avail gap-total)))
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(grow-total (reduce #'+ (mapcar #'layout-node-grow children)))
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(shrink-total (reduce #'+ (mapcar #'layout-node-shrink children))))
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(mapcar (lambda (c sz)
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(let ((g (layout-node-grow c))
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(s (layout-node-shrink c))
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(size sz))
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(when (and (plusp remaining) (plusp grow-total))
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(incf size (round (* remaining (/ g grow-total)))))
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(when (and (minusp remaining) (plusp shrink-total))
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(decf size (round (* (abs remaining) (/ s shrink-total)))))
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(max 1 size)))
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children sizes)))
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(defun compute-layout (root available-width available-height)
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(labels ((place-children (node x y max-w max-h)
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(let* ((children (reverse (layout-node-children node)))
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(is-row (eql (layout-node-direction node) :row))
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(pl (box-edge (layout-node-padding node) :left))
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(pt (box-edge (layout-node-padding node) :top))
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(pr (box-edge (layout-node-padding node) :right))
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(pb (box-edge (layout-node-padding node) :bottom))
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(cw (max 0 (- max-w pl pr)))
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(ch (max 0 (- max-h pt pb)))
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(gap (layout-node-gap node))
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(sizes (distribute-sizes children (if is-row cw ch) gap)))
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(setf (layout-node-x node) (+ x pl)
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(layout-node-y node) (+ y pt))
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(loop with pos = 0
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for child in children
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for size in sizes
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do (if is-row
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(setf (layout-node-width child) size
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(layout-node-x child) (+ x pl pos)
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(layout-node-height child) ch
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(layout-node-y child) (+ y pt))
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(setf (layout-node-height child) size
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(layout-node-y child) (+ y pt pos)
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(layout-node-width child) cw
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(layout-node-x child) (+ x pl)))
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(place-children child (layout-node-x child) (layout-node-y child)
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(if is-row size cw) (if is-row ch size))
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(incf pos (+ size gap))))
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(let ((last (car (last children))))
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(if is-row
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(setf (layout-node-width node)
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(or (layout-node-fixed-width node)
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(if last (+ (layout-node-x node) (layout-node-width last) (box-edge (layout-node-padding node) :right)) max-w))
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(layout-node-height node) max-h)
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(setf (layout-node-height node)
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(or (layout-node-fixed-height node)
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(if last (+ (layout-node-y node) (layout-node-height last) (box-edge (layout-node-padding node) :bottom)) max-h))
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(layout-node-width node) max-w)))))
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(place-children root 0 0 available-width available-height)
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root))
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;; ── Macros ─────────────────────────────────────────────────────
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(defmacro vbox ((&key grow shrink padding margin gap width height) &body children)
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(let ((n (gensym)))
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`(let ((,n (make-layout-node :direction :column
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,@(when grow `(:grow ,grow))
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,@(when shrink `(:shrink ,shrink))
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,@(when padding `(:padding ,padding))
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,@(when margin `(:margin ,margin))
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,@(when gap `(:gap ,gap))
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,@(when width `(:width ,width))
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,@(when height `(:height ,height)))))
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,@(loop for c in children collect `(layout-node-add-child ,n ,c))
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,n)))
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(defmacro hbox ((&key grow shrink padding margin gap width height) &body children)
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(let ((n (gensym)))
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`(let ((,n (make-layout-node :direction :row
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,@(when grow `(:grow ,grow))
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,@(when shrink `(:shrink ,shrink))
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,@(when padding `(:padding ,padding))
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,@(when margin `(:margin ,margin))
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,@(when gap `(:gap ,gap))
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,@(when width `(:width ,width))
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,@(when height `(:height ,height)))))
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,@(loop for c in children collect `(layout-node-add-child ,n ,c))
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,n)))
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(defmacro spacer (&key grow)
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`(make-layout-node :grow ,(or grow 1)))
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