video/.agents/skills/remotion-best-practices/rules/measuring-text.md

name, description, metadata

name	description	metadata
measuring-text	Measuring text dimensions, fitting text to containers, and checking overflow	tags measure, text, layout, dimensions, fitText, fillTextBox

Measuring text in Remotion

Prerequisites

Install @remotion/layout-utils if it is not already installed:

npx remotion add @remotion/layout-utils

Measuring text dimensions

Use measureText() to calculate the width and height of text:

import { measureText } from "@remotion/layout-utils";

const { width, height } = measureText({
  text: "Hello World",
  fontFamily: "Arial",
  fontSize: 32,
  fontWeight: "bold",
});

Results are cached - duplicate calls return the cached result.

Fitting text to a width

Use fitText() to find the optimal font size for a container:

import { fitText } from "@remotion/layout-utils";

const { fontSize } = fitText({
  text: "Hello World",
  withinWidth: 600,
  fontFamily: "Inter",
  fontWeight: "bold",
});

return (
  <div
    style={{
      fontSize: Math.min(fontSize, 80), // Cap at 80px
      fontFamily: "Inter",
      fontWeight: "bold",
    }}
  >
    Hello World
  </div>
);

Checking text overflow

Use fillTextBox() to check if text exceeds a box:

import { fillTextBox } from "@remotion/layout-utils";

const box = fillTextBox({ maxBoxWidth: 400, maxLines: 3 });

const words = ["Hello", "World", "This", "is", "a", "test"];
for (const word of words) {
  const { exceedsBox } = box.add({
    text: word + " ",
    fontFamily: "Arial",
    fontSize: 24,
  });
  if (exceedsBox) {
    // Text would overflow, handle accordingly
    break;
  }
}

Best practices

Load fonts first: Only call measurement functions after fonts are loaded.

import { loadFont } from "@remotion/google-fonts/Inter";

const { fontFamily, waitUntilDone } = loadFont("normal", {
  weights: ["400"],
  subsets: ["latin"],
});

waitUntilDone().then(() => {
  // Now safe to measure
  const { width } = measureText({
    text: "Hello",
    fontFamily,
    fontSize: 32,
  });
});

Use validateFontIsLoaded: Catch font loading issues early:

measureText({
  text: "Hello",
  fontFamily: "MyCustomFont",
  fontSize: 32,
  validateFontIsLoaded: true, // Throws if font not loaded
});

Match font properties: Use the same properties for measurement and rendering:

const fontStyle = {
  fontFamily: "Inter",
  fontSize: 32,
  fontWeight: "bold" as const,
  letterSpacing: "0.5px",
};

const { width } = measureText({
  text: "Hello",
  ...fontStyle,
});

return <div style={fontStyle}>Hello</div>;

Avoid padding and border: Use outline instead of border to prevent layout differences:

<div style={{ outline: "2px solid red" }}>Text</div>