Constraint Recipes (Cookbook)

This page is a practical cookbook for building responsive, relational layouts with Rezi constraints.

Default path:

Use helper constraints (visibilityConstraints, widthConstraints, heightConstraints, spaceConstraints, groupConstraints, conditionalConstraints)

Advanced path:

Use expr("...") when you need a custom relationship not covered by helpers

1) Responsive sidebars and rails (`display`)

ui.row({ gap: 1, width: "full", height: "full" }, [
  ui.box(
    {
      id: "nav",
      width: widthConstraints.clampedPercentOfParent({ ratio: 0.22, min: 18, max: 32 }),
      display: visibilityConstraints.viewportWidthAtLeast(70),
      border: "single",
      p: 1,
    },
    [ui.text("Navigation")],
  ),
  ui.box(
    {
      id: "main",
      width: spaceConstraints.remainingWidth({ subtract: [{ id: "nav" }, { id: "rail" }], minus: 2 }),
      border: "single",
      p: 1,
    },
    [ui.text("Main content")],
  ),
  ui.box(
    {
      id: "rail",
      width: widthConstraints.clampedPercentOfParent({ ratio: 0.28, min: 26, max: 44 }),
      display: visibilityConstraints.viewportAtLeast({ width: 110, height: 28 }),
      border: "single",
      p: 1,
    },
    [ui.text("Detail rail")],
  ),
])

2) Equal-width “key/value” rows (label equalization)

Use max_sibling(#id.min_w) through groupConstraints.maxSiblingMinWidth(...) to align labels that share an id under the same parent container.

const rows = entries.map((e) =>
  ui.row({ key: e.key, gap: 2, wrap: true }, [
    ui.box(
      {
        id: "kv-key",
        width: groupConstraints.maxSiblingMinWidth("kv-key"),
        border: "none",
        p: 0,
      },
      [ui.text(e.key, { dim: true })],
    ),
    ui.box({ flex: 1, border: "none", p: 0 }, [ui.text(e.value)]),
  ]),
)

Example source:

Public starter set

3) Intrinsic-aware modals (content-driven but bounded)

ui.modal({
  id: "help",
  title: "Commands",
  width: widthConstraints.clampedIntrinsicPlus({ pad: 8, min: 44, max: "parent" }),
  height: heightConstraints.clampedIntrinsicPlus({ pad: 4, min: 10, max: "parent" }),
  content: ui.column({ gap: 1 }, [
    ui.text("q : quit"),
    ui.text("h : close"),
  ]),
})

4) Viewport-derived clamping (avoid fragile math strings)

ui.box({
  width: widthConstraints.clampedViewportMinus({ minus: 4, min: 20, max: 140 }),
  height: heightConstraints.clampedViewportMinus({ minus: 4, min: 8, max: 40 }),
})

Example source:

Public starter set

5) Conditional sizing (“if-like” intent)

width: conditionalConstraints.ifThenElse(
  visibilityConstraints.viewportWidthAtLeast(120),
  60,
  100,
)

6) Responsive grid (alpha contract)

Because grid.columns: expr(...) is intentionally invalid in alpha, build two grids and switch with display.

ui.column({ gap: 1 }, [
  ui.grid({ columns: 2, display: visibilityConstraints.viewportWidthBelow(110), gap: 1 }, compactTiles),
  ui.grid({ columns: "1fr 1fr 1fr 1fr", display: visibilityConstraints.viewportWidthAtLeast(110), gap: 1 }, wideTiles),
])

7) Avoid cycles

Sibling references can create cycles when two nodes depend on each other.

Bad:

ui.box({ id: "a", width: expr("#b.w * 2") })
ui.box({ id: "b", width: expr("#a.w / 2") })

Good (anchor one side to parent/viewport/intrinsic):

ui.box({ id: "a", width: widthConstraints.clampedPercentOfParent({ ratio: 0.33, min: 10, max: 40 }) })
ui.box({ id: "b", width: expr("#a.w * 2") })