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Extract Lottie text layout module and align rendering with Lottie spec #18333

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Merged
VicenteCartas merged 3 commits into from
Apr 17, 2026
Merged

Extract Lottie text layout module and align rendering with Lottie spec #18333

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3ba2548
Task 6.1: Extract Lottie text layout module and align rendering with …
VicenteCartas Apr 16, 2026
9a1080d
Merge branch 'master' into lottie-text-layout
VicenteCartas Apr 17, 2026
efd1b9f
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VicenteCartas Apr 17, 2026
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62 changes: 14 additions & 48 deletions packages/dev/lottiePlayer/src/maths/boundingBox.ts
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Original file line number Diff line number Diff line change
@@ -1,14 +1,6 @@
import {
type RawElement,
type RawFont,
type RawEllipseShape,
type RawPathShape,
type RawRectangleShape,
type RawStrokeShape,
type RawTextData,
type RawTextDocument,
} from "../parsing/rawTypes";
import { type RawElement, type RawFont, type RawEllipseShape, type RawPathShape, type RawRectangleShape, type RawStrokeShape, type RawTextData } from "../parsing/rawTypes";
import { GetInitialVectorValues, GetInitialBezierData } from "../parsing/rawPropertyHelpers";
import { ApplyLottieTextContext, MeasureLottieText, ResolveLottieText } from "../parsing/textLayout";

/**
* Represents a bounding box for a shape in the animation.
Expand Down Expand Up @@ -114,55 +106,29 @@ export function GetTextBoundingBox(
variables: Map<string, string>
): BoundingBox | undefined {
spritesCanvasContext.save();
let textInfo: RawTextDocument | undefined = undefined;
if (textData.d && textData.d.k && textData.d.k.length > 0) {
textInfo = textData.d.k[0].s as RawTextDocument;
}

if (!textInfo) {
spritesCanvasContext.restore();
return undefined;
}

const fontSize = textInfo.s;
const fontFamily = textInfo.f;
const finalFont = rawFonts.get(fontFamily);
if (!finalFont) {
const resolvedText = ResolveLottieText(textData, rawFonts, variables);
if (!resolvedText) {
spritesCanvasContext.restore();
return undefined;
}

const weight = finalFont.fWeight || "400"; // Default to normal weight if not specified
spritesCanvasContext.font = `${weight} ${fontSize}px ${finalFont.fFamily}`;

if (textInfo.sc !== undefined && textInfo.sc.length >= 3 && textInfo.sw !== undefined && textInfo.sw > 0) {
spritesCanvasContext.lineWidth = textInfo.sw;
}

// Text is supported as a possible variable (for localization for example)
// Check if the text is a variable and replace it if it is
let text = textInfo.t;
const variableText = variables.get(text);
if (variableText !== undefined) {
text = variableText;
}
const metrics = spritesCanvasContext.measureText(text);
ApplyLottieTextContext(spritesCanvasContext, resolvedText);

const widthPx = Math.ceil(metrics.width);
const heightPx = Math.ceil(metrics.actualBoundingBoxAscent) + Math.ceil(metrics.actualBoundingBoxDescent);
const layout = MeasureLottieText(resolvedText, (text) => spritesCanvasContext.measureText(text));

spritesCanvasContext.restore();

return {
width: widthPx,
height: heightPx,
centerX: widthPx / 2,
centerY: heightPx / 2,
offsetX: 0, // The bounding box calculated by the canvas for the text is always centered in (0, 0)
offsetY: 0, // The bounding box calculated by the canvas for the text is always centered in (0, 0)
width: layout.width,
height: layout.height,
centerX: layout.width / 2,
centerY: layout.height / 2,
offsetX: layout.offsetX,
offsetY: layout.offsetY,
strokeInset: 0, // Text bounding box ignores stroke padding here
actualBoundingBoxAscent: metrics.actualBoundingBoxAscent,
actualBoundingBoxDescent: metrics.actualBoundingBoxDescent,
actualBoundingBoxAscent: layout.baselineOffsetY,
actualBoundingBoxDescent: layout.descent,
};
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}

Expand Down
2 changes: 2 additions & 0 deletions packages/dev/lottiePlayer/src/parsing/rawTypes.ts
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Expand Up @@ -257,6 +257,8 @@ export type RawTextDocumentKeyframe = {
};

export type RawTextDocument = {
sz?: number[]; // Paragraph box size [width, height]
ps?: number[]; // Paragraph box top-left position [x, y] relative to the text layer origin
f: string; // Font family
s: number; // Font size
lh: number; // Line height
Expand Down
58 changes: 20 additions & 38 deletions packages/dev/lottiePlayer/src/parsing/spritePacker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -15,9 +15,9 @@ import {
type RawRectangleShape,
type RawStrokeShape,
type RawTextData,
type RawTextDocument,
} from "./rawTypes";
import { GetInitialScalarValue, GetInitialVectorValues, GetInitialBezierData } from "./rawPropertyHelpers";
import { ApplyLottieTextContext, DrawLottieText, MeasureLottieText, ResolveLottieText } from "./textLayout";

import { type BoundingBox, GetShapesBoundingBox, GetTextBoundingBox } from "../maths/boundingBox";

Expand Down Expand Up @@ -243,7 +243,7 @@ export class SpritePacker {
const page = this._getPageWithRoom(this._spriteAtlasInfo.cellWidth, this._spriteAtlasInfo.cellHeight);

// Draw the text in the canvas
this._drawText(textData, boundingBox, scalingFactor, page);
this._drawText(textData, scalingFactor, page);
this._extrudeSpriteEdges(page, page.currentX, page.currentY, this._spriteAtlasInfo.cellWidth, this._spriteAtlasInfo.cellHeight);
page.isDirty = true;

Expand Down Expand Up @@ -473,66 +473,48 @@ export class SpritePacker {
page.context.restore();
}

private _drawText(textData: RawTextData, boundingBox: BoundingBox, scalingFactor: IVector2Like, page: AtlasPage): void {
private _drawText(textData: RawTextData, scalingFactor: IVector2Like, page: AtlasPage): void {
if (this._rawFonts === undefined) {
return;
}

const textInfo = textData.d.k[0].s as RawTextDocument;

const fontFamily = textInfo.f;
const finalFont = this._rawFonts.get(fontFamily);
if (!finalFont) {
const resolvedText = ResolveLottieText(textData, this._rawFonts, this._variables);
if (!resolvedText) {
return;
}

page.context.save();
page.context.translate(page.currentX, page.currentY);
page.context.scale(scalingFactor.x, scalingFactor.y);

// Set up font (same setup as GetTextBoundingBox for measurement consistency)
const weight = finalFont.fWeight || "400";
page.context.font = `${weight} ${textInfo.s}px ${finalFont.fFamily}`;

if (textInfo.sc !== undefined && textInfo.sc.length >= 3 && textInfo.sw !== undefined && textInfo.sw > 0) {
page.context.lineWidth = textInfo.sw;
}

// Clip to cell bounds to prevent text overdraw into adjacent cells
page.context.beginPath();
page.context.rect(0, 0, boundingBox.width, boundingBox.height);
page.context.clip();

if (textInfo.fc !== undefined && textInfo.fc.length >= 3) {
const rawFillStyle = textInfo.fc;
// Resolve fill color, including the variable-name indirection (fc can be a string variable name).
if (resolvedText.textInfo.fc !== undefined && resolvedText.textInfo.fc.length >= 3) {
const rawFillStyle = resolvedText.textInfo.fc;
if (Array.isArray(rawFillStyle)) {
// If the fill style is an array, we assume it's a color array
page.context.fillStyle = this._lottieColorToCSSColor(rawFillStyle, 1);
} else {
// If it's a string, we need to get the value from the variables map
const variableFillStyle = this._variables.get(rawFillStyle);
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if (variableFillStyle !== undefined) {
page.context.fillStyle = variableFillStyle;
}
}
}

if (textInfo.sc !== undefined && textInfo.sc.length >= 3 && textInfo.sw !== undefined && textInfo.sw > 0) {
page.context.strokeStyle = this._lottieColorToCSSColor(textInfo.sc, 1);
if (resolvedText.hasStroke) {
// ResolveLottieText only sets hasStroke when sc is present and well-formed, so the non-null assertion here is safe.
page.context.strokeStyle = this._lottieColorToCSSColor(resolvedText.textInfo.sc!, 1);
}

// Text is supported as a possible variable (for localization for example)
// Check if the text is a variable and replace it if it is
let text = textInfo.t;
const variableText = this._variables.get(text);
if (variableText !== undefined) {
text = variableText;
}
ApplyLottieTextContext(page.context, resolvedText);

page.context.fillText(text, 0, boundingBox.actualBoundingBoxAscent!);
if (textInfo.sc !== undefined && textInfo.sc.length >= 3 && textInfo.sw !== undefined && textInfo.sw > 0 && textInfo.of === true) {
page.context.strokeText(text, 0, boundingBox.actualBoundingBoxAscent!);
}
const layout = MeasureLottieText(resolvedText, (text) => page.context.measureText(text));

// Clip to cell bounds to prevent text overdraw into adjacent cells
page.context.beginPath();
page.context.rect(0, 0, layout.width, layout.height);
page.context.clip();

DrawLottieText(page.context, resolvedText, layout);

page.context.restore();
}
Expand Down
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