From f75b5d3fd28349ee69f03be34c1316122992c283 Mon Sep 17 00:00:00 2001
From: Maze Winther <mazewinther@gmail.com>
Date: Wed, 25 Feb 2026 01:37:56 +0100
Subject: fix a ton of issues + improvement

---
 apps/web/src/lib/text/layout.ts | 167 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 167 insertions(+)
 create mode 100644 apps/web/src/lib/text/layout.ts

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

diff --git a/apps/web/src/lib/text/layout.ts b/apps/web/src/lib/text/layout.ts
new file mode 100644
index 00000000..8c38e9aa
--- /dev/null
+++ b/apps/web/src/lib/text/layout.ts
@@ -0,0 +1,167 @@
+import { DEFAULT_TEXT_BACKGROUND } from "@/constants/text-constants";
+import type { TextElement } from "@/types/timeline";
+
+type TextRect = {
+	left: number;
+	top: number;
+	width: number;
+	height: number;
+};
+
+export interface TextBlockMeasurement {
+	visualCenterOffset: number;
+	height: number;
+	maxWidth: number;
+}
+
+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,
+	fallbackFontSize,
+}: {
+	lineMetrics: TextMetrics[];
+	lineHeightPx: number;
+	fallbackFontSize: number;
+}): TextBlockMeasurement {
+	let top = Number.POSITIVE_INFINITY;
+	let bottom = Number.NEGATIVE_INFINITY;
+	let maxWidth = 0;
+
+	for (let index = 0; index < lineMetrics.length; index++) {
+		const metrics = lineMetrics[index];
+		const lineY = index * lineHeightPx;
+		top = Math.min(
+			top,
+			lineY - getMetricAscent({ metrics, fallbackFontSize }),
+		);
+		bottom = Math.max(
+			bottom,
+			lineY + getMetricDescent({ metrics, fallbackFontSize }),
+		);
+		maxWidth = Math.max(maxWidth, metrics.width);
+	}
+
+	const height = bottom - top;
+	const visualCenterOffset = (top + bottom) / 2;
+
+	return { visualCenterOffset, height, maxWidth };
+}
+
+function getTextRect({
+	textAlign,
+	block,
+}: {
+	textAlign: TextElement["textAlign"];
+	block: TextBlockMeasurement;
+}): TextRect {
+	const left =
+		textAlign === "left" ? 0 : textAlign === "right" ? -block.maxWidth : -block.maxWidth / 2;
+
+	return {
+		left,
+		top: -block.height / 2,
+		width: block.maxWidth,
+		height: block.height,
+	};
+}
+
+function isTextBackgroundVisible({
+	background,
+}: {
+	background: TextElement["background"];
+}): boolean {
+	return Boolean(background.color) && background.color !== "transparent";
+}
+
+export function getTextBackgroundRect({
+	textAlign,
+	block,
+	background,
+	fontSizeRatio = 1,
+}: {
+	textAlign: TextElement["textAlign"];
+	block: TextBlockMeasurement;
+	background: TextElement["background"];
+	fontSizeRatio?: number;
+}): TextRect | null {
+	if (!isTextBackgroundVisible({ background })) {
+		return null;
+	}
+
+	const textRect = getTextRect({ textAlign, block });
+	const paddingX =
+		(background.paddingX ?? DEFAULT_TEXT_BACKGROUND.paddingX) * fontSizeRatio;
+	const paddingY =
+		(background.paddingY ?? DEFAULT_TEXT_BACKGROUND.paddingY) * fontSizeRatio;
+	const offsetX = background.offsetX ?? DEFAULT_TEXT_BACKGROUND.offsetX;
+	const offsetY = background.offsetY ?? DEFAULT_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: TextElement["background"];
+	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,
+	};
+}
-- 
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