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import type { Getter } from "melt";
import { extract } from "./extract.svelte.js";
import { useResizeObserver, watch } from "runed";
import { tick } from "svelte";
export interface TextareaAutosizeOptions {
/** Textarea element to autosize. */
element: Getter<HTMLElement | undefined>;
/** Textarea content. */
input: Getter<string>;
/** Function called when the textarea size changes. */
onResize?: () => void;
/**
* Specify the style property that will be used to manipulate height. Can be `height | minHeight`.
* @default `height`
**/
styleProp?: "height" | "minHeight";
}
export class TextareaAutosize {
#options: TextareaAutosizeOptions;
element = $derived.by(() => extract(this.#options.element));
input = $derived.by(() => extract(this.#options.input));
styleProp = $derived.by(() => extract(this.#options.styleProp, "height"));
textareaScrollHeight = $state(1);
textareaOldWidth = $state(0);
constructor(options: TextareaAutosizeOptions) {
this.#options = options;
watch([() => this.input, () => this.element], () => {
tick().then(() => this.triggerResize());
});
watch(
() => this.textareaScrollHeight,
() => options?.onResize?.()
);
useResizeObserver(
() => this.element,
([entry]) => {
if (!entry) return;
const { contentRect } = entry;
if (this.textareaOldWidth === contentRect.width) return;
requestAnimationFrame(() => {
this.textareaOldWidth = contentRect.width;
this.triggerResize();
});
}
);
}
triggerResize() {
if (!this.element) return;
let height = "";
this.element.style[this.styleProp] = "1px";
this.textareaScrollHeight = this.element?.scrollHeight;
height = `${this.textareaScrollHeight}px`;
this.element.style[this.styleProp] = height;
}
}
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