combobox: improved picker width behaviour

add width behaviour options, fix match width

src/lib/Combobox.svelte

@@ -41,7 +41,6 @@
 	import Label from './Label.svelte';
 	import StyledRawInput from './StyledRawInput.svelte';
 	import { InputValidatorEvent, validate, type ValidatorOptions } from '@svelte-toolkit/validate';
-	import type { Action } from 'svelte/action';
 	import { onMount, tick, untrack, type Snippet } from 'svelte';
 	import { Portal } from '@jsrob/svelte-portal';
 	import { scale } from 'svelte/transition';
@@ -52,6 +51,7 @@
 	import type { KeyOption } from 'match-sorter';
 	import { Tween } from 'svelte/motion';
 	import { cubicOut } from 'svelte/easing';
+	import type { Attachment } from 'svelte/attachments';
 
 	interface Props {
 		/**
@@ -104,11 +104,16 @@
 		/** Bindable open state of the combobox */
 		open?: boolean;
 		/**
-		 * If enabled, matches the picker width to the input width. Otherwise,
-		 * the picker width is determined by the average of its content, with
-		 * a reasonable minimum (default: false).
+		 * Determines picker width based on content with four options:
+		 * `match`: matches the input width
+		 * `average`: calculates average width based on the length of option
+		 *  content, with a reasonable minimum
+		 * `longest`: sets width based on the longest option, which can lead to
+		 * excessively wide pickers but tries to prevent wrapping
+		 * `max-match` (default): sets width based on the maximum of the input
+		 * width and the longest option
 		 */
-		matchWidth?: boolean;
+		pickerWidth?: 'match' | 'average' | 'longest' | 'max-match';
 		/** Uses a compact layout for the search input with less padding and smaller text */
 		compact?: boolean;
 		/**
@@ -182,7 +187,7 @@
 		value = $bindable<ComboboxOption | undefined>(undefined),
 		open = $bindable(false),
 		usePreview = 'auto',
-		matchWidth = false,
+		pickerWidth = 'average',
 		options,
 		required = false,
 		invalidMessage = 'Please select an option',
@@ -223,7 +228,6 @@
 	let pickerContainer = $state<HTMLDivElement | null>(null);
 
 	// TODO: there's something weird with dropdown placement on narrow screens
-	// TODO: match width to input isn't working properly for vconf selectors
 
 	/** options filtered by search value and searchKeys */
 	const filteredItems = $derived.by(() => {
@@ -355,26 +359,58 @@
 		onchange?.(newValue);
 	};
 
-	/** sets minimum width of the picker as configured by props */
-	const minWidth: Action<HTMLDivElement, { options: ComboboxOption[] }> = (
-		container,
-		buildOpts
-	) => {
-		const f = (opts: typeof buildOpts) => {
-			if (matchWidth && searchInput) {
-				container.style.width = searchInput.scrollWidth + 'px';
-				return;
-			}
-
-			const options = opts.options;
-			if (options.length === 0) return;
-			const avg = options.reduce((acc, item) => acc + getLabel(item).length, 0) / options.length;
-			container.style.width = `${avg * 2.5}ch`;
+	/**
+	 * Calculates average width based on provided options returning an estimated
+	 * width in 'ch' units or a reasonable minimum when no options are provided.
+	 */
+	const calculateAvgWidth = (opts: ComboboxOption[]) => {
+		if (opts.length === 0) return '10ch'; // reasonable minimum width when no options
+		const labelAvg = opts.reduce((acc, item) => acc + getLabel(item).length, 0) / opts.length;
+		const infotextAvg =
+			opts.reduce((acc, item) => acc + (item.infotext ? item.infotext.length : 0), 0) / opts.length;
+		const avgWidth = labelAvg * 2 + infotextAvg * 1.5 + (infotextAvg > 0 ? 10 : 0);
+		return `${Math.max(avgWidth, 10)}ch`;
 	};
-		f(buildOpts);
-		return {
-			update: (updateOpts: typeof buildOpts) => {
-				f(updateOpts);
+
+	/**
+	 * Calculates longest width based on provided options, attempting to prevent
+	 * wrapping by returning a width in 'ch' units based on the longest label and
+	 * infotext, or a reasonable minimum when no options are provided.
+	 */
+	const calculateLongestWidth = (opts: ComboboxOption[]) => {
+		if (opts.length === 0) return '10ch'; // reasonable minimum width when no options
+		const longestLabel = Math.max(...opts.map((item) => getLabel(item).length));
+		const longestInfotext = Math.max(
+			...opts.map((item) => (item.infotext ? item.infotext.length : 0))
+		);
+		const longestWidth = longestLabel * 2 + longestInfotext * 1.5 + (longestInfotext > 0 ? 10 : 0);
+		return `${Math.max(longestWidth, 10)}ch`;
+	};
+
+	/** sets minimum width of the picker as configured by props */
+	const minWidth = (opts: {
+		options: ComboboxOption[];
+		matchElem: HTMLInputElement | null;
+		mode: Props['pickerWidth'];
+	}): Attachment<HTMLDivElement> => {
+		return (elem) => {
+			if ((opts.mode === 'match' || opts.options.length === 0) && opts.matchElem) {
+				// match width if explicitly enabled, or no options to average
+				elem.style.width = opts.matchElem.offsetWidth + 'px';
+				console.log('matched', elem.style.width, 'to', opts.matchElem.offsetWidth);
+			} else {
+				// otherwise, set width based on average content width
+				let val = '10ch';
+				if (opts.mode === 'average') {
+					val = calculateAvgWidth(opts.options);
+				} else if (opts.mode === 'longest' || opts.mode === 'max-match') {
+					val = calculateLongestWidth(opts.options);
+					if (opts.mode === 'max-match') {
+						elem.style.maxWidth = opts.matchElem ? opts.matchElem.offsetWidth + 'px' : 'none';
+					}
+				}
+				elem.style.width = val;
+				console.log('averaged', val);
 			}
 		};
 	};
@@ -526,7 +562,6 @@
 				open && pickerPosition === 'top' && 'mb-[var(--outer-gap)]',
 				open && pickerPosition === 'bottom' && 'mt-[var(--outer-gap)]'
 			]}
-			use:minWidth={{ options: options }}
 			bind:this={pickerContainer}
 			transition:scale={{ duration: 200 }}
 			role="listbox"
@@ -547,6 +582,7 @@
 				onscroll({ event: e, top: atTop, bottom: atBottom, searchInput: searchInput?.value ?? '' });
 			}}
 			tabindex="0"
+			{@attach minWidth({ options, mode: pickerWidth, matchElem: searchInput })}
 		>
 			{#each filteredItems as opt (opt.value)}
 				{@render option(opt)}

src/lib/TimezoneInput.svelte

@@ -120,7 +120,7 @@
 	{required}
 	bind:value={timezone}
 	{options}
-	matchWidth
+	pickerWidth="match"
 	placeholder="Select a timezone"
 	class={classValue}
 />

src/routes/+page.svelte

@@ -184,6 +184,7 @@
 			]}
 			onchange={(e) => console.log('Selected:', e.value)}
 			onvalidate={(e) => console.log('Validation:', e.detail)}
+			pickerWidth="max-match"
 		>
 			{#snippet labelRender(opt: ComboboxOption)}
 				Processed {opt.label}