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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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