From 3e89d2998588f8e35c524e523ba2ee853f0f6475 Mon Sep 17 00:00:00 2001
From: Maze Winther <mazewinther@gmail.com>
Date: Mon, 20 Apr 2026 11:31:17 +0200
Subject: refactor: restructure files to their domains,  new preview overlay
 system, and dep graph

---
 apps/web/src/text/layout.ts | 226 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 226 insertions(+)
 create mode 100644 apps/web/src/text/layout.ts

(limited to 'apps/web/src/text/layout.ts')

diff --git a/apps/web/src/text/layout.ts b/apps/web/src/text/layout.ts
new file mode 100644
index 00000000..aabf5ca9
--- /dev/null
+++ b/apps/web/src/text/layout.ts
@@ -0,0 +1,226 @@
+import type { TextBackground, TextElement } from "@/timeline";
+import { DEFAULTS } from "@/timeline/defaults";
+
+type TextRect = {
+	left: number;
+	top: number;
+	width: number;
+	height: number;
+};
+
+export interface TextBlockMeasurement {
+	visualCenterOffset: number;
+	height: number;
+	maxWidth: number;
+}
+
+export type TextCanvasContext =
+	| CanvasRenderingContext2D
+	| OffscreenCanvasRenderingContext2D;
+
+const TEXT_DECORATION_THICKNESS_RATIO = 0.07;
+const STRIKETHROUGH_VERTICAL_RATIO = 0.35;
+
+export function setCanvasLetterSpacing({
+	ctx,
+	letterSpacingPx,
+}: {
+	ctx: TextCanvasContext;
+	letterSpacingPx: number;
+}): void {
+	if ("letterSpacing" in ctx) {
+		(ctx as CanvasRenderingContext2D & { letterSpacing: string }).letterSpacing =
+			`${letterSpacingPx}px`;
+	}
+}
+
+export function getMetricAscent({
+	metrics,
+	fallbackFontSize,
+}: {
+	metrics: TextMetrics;
+	fallbackFontSize: number;
+}): number {
+	return metrics.actualBoundingBoxAscent ?? fallbackFontSize * 0.8;
+}
+
+export function getMetricDescent({
+	metrics,
+	fallbackFontSize,
+}: {
+	metrics: TextMetrics;
+	fallbackFontSize: number;
+}): number {
+	return metrics.actualBoundingBoxDescent ?? fallbackFontSize * 0.2;
+}
+
+export function measureTextBlock({
+	lineMetrics,
+	lineHeightPx,
+}: {
+	lineMetrics: TextMetrics[];
+	lineHeightPx: number;
+}): TextBlockMeasurement {
+	let maxWidth = 0;
+
+	for (const metrics of lineMetrics) {
+		maxWidth = Math.max(maxWidth, metrics.width);
+	}
+
+	const lineCount = lineMetrics.length;
+	const height = lineCount * lineHeightPx;
+	const visualCenterOffset = ((lineCount - 1) * lineHeightPx) / 2;
+
+	return { visualCenterOffset, height, maxWidth };
+}
+
+function getTextRect({
+	textAlign,
+	block,
+}: {
+	textAlign: TextElement["textAlign"];
+	block: TextBlockMeasurement;
+}): TextRect {
+	const textAlignToLeft: Record<typeof textAlign, number> = {
+		left: 0,
+		right: -block.maxWidth,
+		center: -block.maxWidth / 2,
+	};
+	const left = textAlignToLeft[textAlign];
+
+	return {
+		left,
+		top: -block.height / 2,
+		width: block.maxWidth,
+		height: block.height,
+	};
+}
+
+function isTextBackgroundVisible({
+	background,
+}: {
+	background: TextBackground;
+}): boolean {
+	return (
+		background.enabled &&
+		Boolean(background.color) &&
+		background.color !== "transparent"
+	);
+}
+
+export function getTextBackgroundRect({
+	textAlign,
+	block,
+	background,
+	fontSizeRatio = 1,
+}: {
+	textAlign: TextElement["textAlign"];
+	block: TextBlockMeasurement;
+	background: TextBackground;
+	fontSizeRatio?: number;
+}): TextRect | null {
+	if (!isTextBackgroundVisible({ background })) {
+		return null;
+	}
+
+	const textRect = getTextRect({ textAlign, block });
+	const paddingX =
+		(background.paddingX ?? DEFAULTS.text.background.paddingX) * fontSizeRatio;
+	const paddingY =
+		(background.paddingY ?? DEFAULTS.text.background.paddingY) * fontSizeRatio;
+	const offsetX = background.offsetX ?? DEFAULTS.text.background.offsetX;
+	const offsetY = background.offsetY ?? DEFAULTS.text.background.offsetY;
+
+	return {
+		left: textRect.left - paddingX + offsetX,
+		top: textRect.top - paddingY + offsetY,
+		width: textRect.width + paddingX * 2,
+		height: textRect.height + paddingY * 2,
+	};
+}
+
+export function getTextVisualRect({
+	textAlign,
+	block,
+	background,
+	fontSizeRatio = 1,
+}: {
+	textAlign: TextElement["textAlign"];
+	block: TextBlockMeasurement;
+	background: TextBackground;
+	fontSizeRatio?: number;
+}): TextRect {
+	const textRect = getTextRect({ textAlign, block });
+	const backgroundRect = getTextBackgroundRect({
+		textAlign,
+		block,
+		background,
+		fontSizeRatio,
+	});
+
+	if (!backgroundRect) {
+		return textRect;
+	}
+
+	const left = Math.min(textRect.left, backgroundRect.left);
+	const top = Math.min(textRect.top, backgroundRect.top);
+	const right = Math.max(
+		textRect.left + textRect.width,
+		backgroundRect.left + backgroundRect.width,
+	);
+	const bottom = Math.max(
+		textRect.top + textRect.height,
+		backgroundRect.top + backgroundRect.height,
+	);
+
+	return {
+		left,
+		top,
+		width: right - left,
+		height: bottom - top,
+	};
+}
+
+export function drawTextDecoration({
+	ctx,
+	textDecoration,
+	lineWidth,
+	lineY,
+	metrics,
+	scaledFontSize,
+	textAlign,
+}: {
+	ctx: TextCanvasContext;
+	textDecoration: string;
+	lineWidth: number;
+	lineY: number;
+	metrics: TextMetrics;
+	scaledFontSize: number;
+	textAlign: CanvasTextAlign;
+}): void {
+	if (textDecoration === "none" || !textDecoration) return;
+
+	const thickness = Math.max(
+		1,
+		scaledFontSize * TEXT_DECORATION_THICKNESS_RATIO,
+	);
+	const ascent = getMetricAscent({ metrics, fallbackFontSize: scaledFontSize });
+	const descent = getMetricDescent({
+		metrics,
+		fallbackFontSize: scaledFontSize,
+	});
+
+	let xStart = -lineWidth / 2;
+	if (textAlign === "left") xStart = 0;
+	if (textAlign === "right") xStart = -lineWidth;
+
+	if (textDecoration === "underline") {
+		const underlineY = lineY + descent + thickness;
+		ctx.fillRect(xStart, underlineY, lineWidth, thickness);
+	}
+
+	if (textDecoration === "line-through") {
+		const strikeY = lineY - (ascent - descent) * STRIKETHROUGH_VERTICAL_RATIO;
+		ctx.fillRect(xStart, strikeY, lineWidth, thickness);
+	}
+}
-- 
cgit v1.3.1