Constraints

Enforce drag and resize rules.

Constraints are small functions that clamp item position and size during drag or resize. They run in order: grid-level constraints first, then per-item constraints on the LayoutItem.

Built-in constraints

Constraint	Description
`gridBounds`	Keep items inside the grid bounds.
`minMaxSize`	Respect `minW`, `maxW`, `minH`, `maxH` on items.
`containerBounds`	Clamp movement to the visible container height.
`boundedX`	Clamp horizontal movement only.
`boundedY`	Clamp vertical movement only.
`aspectRatio(ratio)`	Maintain a width/height ratio while resizing.
`snapToGrid(stepX, stepY)`	Snap movement to grid steps.
`minSize(minW, minH)`	Enforce minimum size.
`maxSize(maxW, maxH)`	Enforce maximum size.
`defaultConstraints`	`[gridBounds, minMaxSize]`.

Using constraints

import { useState } from "react";
import {
  DndGrid,
  type Layout,
  type LayoutConstraint,
  aspectRatio,
  defaultConstraints,
  snapToGrid,
} from "@dnd-grid/react";

const topBand: LayoutConstraint = {
  name: "topBand(2)",
  constrainPosition(item, x, y) {
    const maxY = Math.max(0, 2 - item.h);
    return { x, y: Math.min(y, maxY) };
  },
};

const layout: Layout = [
  { id: "snap", x: 0, y: 0, w: 4, h: 2 },
  { id: "ratio", x: 4, y: 0, w: 4, h: 2 },
  { id: "band", x: 8, y: 0, w: 4, h: 2, constraints: [topBand] },
];

const constraints = [
  ...defaultConstraints,
  snapToGrid(2, 1),
  aspectRatio(16 / 9),
];

export function ConstraintGrid() {
  const [currentLayout, setLayout] = useState(layout);
  return (
    <DndGrid
      layout={currentLayout}
      cols={12}
      rowHeight={40}
      constraints={constraints}
      onLayoutChange={setLayout}
    >
      {currentLayout.map((item) => (
        <div key={item.id}>{item.id}</div>
      ))}
    </DndGrid>
  );
}

Writing custom constraints

A LayoutConstraint can implement either constrainPosition, constrainSize, or both. The ConstraintContext provides grid metrics and the full layout.

import { type LayoutConstraint } from "@dnd-grid/react";

const lockRightColumn: LayoutConstraint = {
  name: "lockRightColumn",
  constrainPosition(item, x, y, { cols }) {
    const maxX = Math.max(0, cols - item.w);
    return { x: Math.max(x, maxX), y };
  },
};

Constraint utilities

If you are building your own drag interactions, you can apply the same rules manually with the exported helpers.

import {
  applyPositionConstraints,
  applySizeConstraints,
  defaultConstraints,
} from "@dnd-grid/react";

const position = applyPositionConstraints(
  defaultConstraints,
  item,
  nextX,
  nextY,
  context,
);

const size = applySizeConstraints(
  defaultConstraints,
  item,
  nextW,
  nextH,
  handle,
  context,
);