ludic/packages/ludic.ui/layout.ludic
Orkuncakilkaya 1dad96102a feat(ui): ludic.ui is a UI framework - input, controls, render3d backend, the CSS a game needs
A game no longer writes a host:
- The runtime reads Input itself: focus and keyboard navigation (Tab, arrows, Enter/Space,
  autofocus), the pointer (hover, :active, click on release, drag), and scroll boxes with the
  wheel, a draggable scrollbar, clipping and scroll-into-view.
- HTML's controls are built in (button, checkbox, radio, range, select, text, key capture), made
  of plain parts a stylesheet styles, each reporting with on-change and event.value.
- ludic.ui/render3d.ludic draws with render3d's overlay: textures, named atlases (icon:NAME),
  nine-slice border-image, rounded rects and rings, clipping, and a scale.
- Hooks for the program's language, sounds and clock (ui_translator, ui_sounds, ui_clock).
- ui_dev: hot reload, errors on screen, LUDIC_UI_DUMP.
- CSS:
  - colours as #rgb / #rrggbbaa / rgb() / rgba() / names;
  - border-radius and outline (following the radius), box-shadow, background-image and a tinted
    border-image;
  - group opacity, @keyframes / animation, transition;
  - :focus, :focus-visible and :focus-within.
- HTML mixed content, and boolean attributes.
- render3d gains tex_width / tex_height, and the XML reader keeps text runs in order.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-09-24 17:26:09 +03:00

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# layout.ludic - flex layout on the CSS box model, top-down: a box is told how wide it may be,
# measures its content at that width (so a wrapping row knows how tall it is), then places each
# child. A size is the border box: padding and border inside it, margin outside it.
function ly_measure(n: UiNode, avail: float, size: float, fg: int) -> void {
n.rsize = size
if n.size > 0.0 { n.rsize = n.size }
n.rfg = fg
n.rfg_a = ly_fg_a
if n.fg != UI_INHERIT {
n.rfg = n.fg
n.rfg_a = n.fg_a
}
ly_fg_a = n.rfg_a
n.mw = ly_hin(n)
n.mh = ly_vin(n)
if n.kind == UI_TEXT { ly_measure_text(n, avail) }
if n.kind == UI_NATIVE and n.native.measure != null {
let base_w = n.mw
let base_h = n.mh
n.mw = 0.0
n.mh = 0.0
n.native.measure(n, avail)
n.mw = n.mw + base_w
n.mh = n.mh + base_h
}
if n.kind == UI_IMAGE {
n.mw = n.mw + n.rsize
n.mh = n.mh + n.rsize
}
var fixed_w = n.w
if n.w_pct > 0.0 { fixed_w = avail * n.w_pct / 100.0 }
if (n.kind == UI_BOX or n.kind == UI_SCROLL) and n.children != null {
var inner = avail - n.ml - n.mr
if fixed_w > 0.0 { inner = fixed_w }
inner = ly_clamp(inner, n.min_w, n.max_w) - ly_hin(n)
if n.dir == UI_ROW and n.wrap { ly_measure_wrap(n, inner) } else { ly_measure_box(n, inner) }
}
n.content_h = n.mh
if fixed_w > 0.0 { n.mw = fixed_w }
if n.h > 0.0 { n.mh = n.h }
n.mw = ly_clamp(n.mw, n.min_w, n.max_w)
n.mh = ly_clamp(n.mh, n.min_h, n.max_h)
}
var ly_fg_a: float = 1.0
function ly_hin(n: UiNode) -> float { return n.pl + n.pr + n.border * 2.0 }
function ly_vin(n: UiNode) -> float { return n.pt + n.pb + n.border * 2.0 }
function ly_clamp(v: float, lo: float, hi: float) -> float {
var out = v
if hi > 0.0 and out > hi { out = hi }
if out < lo { out = lo }
return out
}
function ly_measure_box(n: UiNode, inner: float) -> void {
var main = 0.0
var cross = 0.0
var count = 0
for i in 0 .. len(n.children) {
let c = n.children[i]
ly_fg_a = n.rfg_a
ly_measure(c, inner, n.rsize, n.rfg)
if c.pos < 2 {
main = main + ly_main(c, n.dir)
if count > 0 { main = main + n.gap }
cross = Math.max(cross, ly_cross(c, n.dir))
count += 1
}
}
if n.dir == UI_ROW {
n.mw = n.mw + main
n.mh = n.mh + cross
} else {
n.mw = n.mw + cross
n.mh = n.mh + main
}
}
# a wrapping row: children in lines no wider than `inner`, the lines stacked `gap` apart
function ly_measure_wrap(n: UiNode, inner: float) -> void {
var line_w = 0.0
var line_h = 0.0
var widest = 0.0
var total = 0.0
var count = 0
for i in 0 .. len(n.children) {
let c = n.children[i]
ly_fg_a = n.rfg_a
ly_measure(c, inner, n.rsize, n.rfg)
if c.pos >= 2 { continue }
let cw = ly_main(c, UI_ROW)
if count > 0 and line_w + n.gap + cw > inner {
widest = Math.max(widest, line_w)
total = total + line_h + n.gap
line_w = 0.0
line_h = 0.0
count = 0
}
if count > 0 { line_w = line_w + n.gap }
line_w = line_w + cw
line_h = Math.max(line_h, ly_cross(c, UI_ROW))
count += 1
}
n.mw = n.mw + Math.max(widest, line_w)
n.mh = n.mh + total + line_h
}