✨ feat: start working on #11

src/lib/Pane.svelte

@@ -1,10 +1,11 @@
 <script lang="ts">
 	import { getContext, onMount, onDestroy } from 'svelte';
+	import { writable } from 'svelte/store';
 	import type { Action } from 'svelte/action';
 	import { KEY } from './Splitpanes.svelte';
 	import type { IPane, SplitContext } from '.';
 
-	const { onPaneInit, onPaneAdd, onPaneRemove, onPaneClick, isHorizontal, showFirstSplitter, veryFirstPaneKey } =
+	const { onPaneInit, onPaneAdd, onPaneRemove, onPaneClick, isHorizontal, showFirstSplitter } =
 		getContext<SplitContext>(KEY);
 
 	// PROPS
@@ -22,6 +23,11 @@
 	const key = {};
 	let element: HTMLElement;
 	let sz: number = size == null ? 0 : size;
+	const sizeStore = writable({
+		size,
+		minSize,
+		maxSize
+	});
 
 	const isBrowser = typeof window !== 'undefined';
 
@@ -31,6 +37,14 @@
 		sz = size;
 	}
 
+	$: {
+		sizeStore.update((details) => {
+			details.minSize = minSize;
+			details.maxSize = maxSize;
+			return details;
+		});
+	}
+
 	$: dimension = $isHorizontal ? 'height' : 'width';
 
 	$: style =
@@ -42,7 +56,8 @@
 			.filter((value) => value !== undefined)
 			.join(' ') || undefined;
 
-	const { onSplitterDown, onSplitterClick, onSplitterDblClick } = onPaneInit(key);
+	const result = onPaneInit(key, sizeStore);
+	const { onSplitterDown, onSplitterClick, onSplitterDblClick, previousPaneSizeStore } = result;
 
 	function handleMouseClick(event: MouseEvent) {
 		onPaneClick(event, key);
@@ -80,6 +95,10 @@
 				if (size != null) {
 					size = sz;
 				}
+				sizeStore.update((details) => {
+					details.size = v;
+					return details;
+				});
 			},
 			min: () => minSize,
 			max: () => maxSize,
@@ -94,12 +113,29 @@
 </script>
 
 <!-- Splitter -->
-<!-- TODO: Support aria role="separator" and make this a focusable separtor. Sources:
+<!-- TODO: Make this a focusable separtor, and check if it is non-focusable (when minSize=maxSize).
+	Need also:
+	* Let the user control about aria values (such as aria-valuetext), and if it is focusable.default.render
+	* Let the user decide which pane he wish to leave without any seperator description, and describe the rest of them.
+	* Verify it's working in SSR.
+	* Keybinding
+	Sources:
 	* https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/roles/separator_role
 	* https://www.w3.org/WAI/ARIA/apg/patterns/windowsplitter/
 -->
-{#if $veryFirstPaneKey !== key || $showFirstSplitter}
-	<div use:splitterAction class="splitpanes__splitter" />
+{#if $previousPaneSizeStore || $showFirstSplitter}
+	<div
+		use:splitterAction
+		class="splitpanes__splitter"
+		role={$previousPaneSizeStore ? 'separator' : undefined}
+		aria-valuenow={$previousPaneSizeStore?.size ?? undefined}
+		aria-valuemin={$previousPaneSizeStore && $previousPaneSizeStore.minSize > 0
+			? $previousPaneSizeStore.minSize
+			: undefined}
+		aria-valuemax={$previousPaneSizeStore && $previousPaneSizeStore.maxSize < 100
+			? $previousPaneSizeStore.maxSize
+			: undefined}
+	/>
 {/if}
 
 <!-- Pane -->

src/lib/Splitpanes.svelte

@@ -4,8 +4,9 @@
 
 <script lang="ts">
 	import { onMount, onDestroy, setContext, createEventDispatcher, tick } from 'svelte';
-	import { writable } from 'svelte/store';
-	import type { IPane, IPaneSizingEvent, SplitContext, PaneInitFunction } from '.';
+	import { writable, type Readable } from 'svelte/store';
+	import type { SizeDetails, IPane, IPaneSizingEvent, SplitContext, PaneInitFunction } from '.';
+	import { switchableStore } from './internal/store';
 
 	// TYPE DECLARATIONS ----------------
 
@@ -99,7 +100,11 @@
 	let isHorizontal = writable<boolean>(horizontal);
 	const showFirstSplitter = writable<boolean>(firstSplitter);
 	// tells the key of the very first pane, or undefined if not recieved yet
-	const veryFirstPaneKey = writable<any>(undefined);
+	let lastPreviousPanesSizeStoreOnInit: Readable<SizeDetails> | undefined = undefined;
+	const previousPanesSizeStoresData = new Map<
+		any,
+		{ receivedStore: Readable<SizeDetails>; update: (store: Readable<SizeDetails> | undefined) => void }
+	>();
 	let activeSplitterElement: HTMLElement | null = null;
 	let activeSplitterDrag: number | null = null;
 	let startingTDrag: number | null = null;
@@ -115,10 +120,11 @@
 		});
 	}
 
-	const onPaneInit: PaneInitFunction = (key: any) => {
-		if ($veryFirstPaneKey === undefined) {
-			$veryFirstPaneKey = key;
-		}
+	const onPaneInit: PaneInitFunction = (key: any, sizeStore: Readable<SizeDetails>) => {
+		const { store, update } = switchableStore(lastPreviousPanesSizeStoreOnInit, undefined);
+		lastPreviousPanesSizeStoreOnInit = sizeStore;
+
+		previousPanesSizeStoresData.set(key, { receivedStore: sizeStore, update });
 
 		return {
 			onSplitterDown: (e) => {
@@ -137,13 +143,13 @@
 				if (dblClickSplitter) {
 					onSplitterDblClick(e, indexOfPane(key));
 				}
-			}
+			},
+			previousPaneSizeStore: store
 		};
 	};
 
 	setContext<SplitContext>(KEY, {
 		showFirstSplitter,
-		veryFirstPaneKey,
 		isHorizontal,
 		onPaneInit,
 		onPaneAdd,
@@ -159,11 +165,6 @@
 			return el === pane.element;
 		});
 
-		if (index === 0) {
-			// Need to update the first pane key, because the first pane can be changed in runtime.
-			$veryFirstPaneKey = pane.key;
-		}
-
 		//inserts pane at proper array index
 		panes.splice(index, 0, pane);
 
@@ -172,6 +173,20 @@
 			panes[i].index = i;
 		}
 
+		// Update previous size stores both both this pane and for the next one
+		const currentData = previousPanesSizeStoresData.get(pane.key);
+		const previousSizeStoreNow =
+			index === 0 ? undefined : previousPanesSizeStoresData.get(panes[index - 1].key).receivedStore;
+		currentData.update(previousSizeStoreNow);
+
+		if (index < panes.length - 1) {
+			// If isn't not the last one
+			const currentSizeStore = currentData.receivedStore;
+
+			const nextKey = panes[index + 1].key;
+			previousPanesSizeStoresData.get(nextKey).update(currentSizeStore);
+		}
+
 		if (isReady) {
 			await tick();
 
@@ -189,6 +204,7 @@
 	async function onPaneRemove(key: any) {
 		// 1. Remove the pane from array and redo indexes.
 		const index = panes.findIndex((p) => p.key === key);
+		const isNotLast = index < panes.length - 1;
 
 		// race condition - typically happens when the dev server restarts
 		if (index >= 0) {
@@ -199,8 +215,17 @@
 				panes[i].index = i;
 			}
 
-			if (index === 0) {
-				$veryFirstPaneKey = panes.length > 0 ? panes[0].key : undefined;
+			// Update previous size stores both both this pane and for the next one
+			previousPanesSizeStoresData.get(key).update(undefined);
+
+			if (isNotLast) {
+				// If not the last one
+				const prevIndex = index - 1;
+				const prevSizeStoreNow =
+					prevIndex === 0 ? undefined : previousPanesSizeStoresData.get(panes[prevIndex].key).receivedStore;
+
+				const nextKey = panes[index].key;
+				previousPanesSizeStoresData.get(nextKey).update(prevSizeStoreNow);
 			}
 
 			if (isReady) {

src/lib/index.ts

@@ -3,16 +3,34 @@ import type { Readable } from 'svelte/store';
 export { default as Splitpanes } from './Splitpanes.svelte';
 export { default as Pane } from './Pane.svelte';
 
-export type PaneInitFunction = (key: any) => {
+export interface SizeDetails {
+	/** The current size of a pane.
+	 *
+	 * If number, it's the real pane size value.
+	 * If null, it means that the pane size is unknown yet.
+	 */
+	size: number | null;
+	minSize: number;
+	maxSize: number;
+}
+
+export type PaneInitFunction = (
+	key: any,
+	sizeStore: Readable<SizeDetails>
+) => {
 	onSplitterDown: (_event: TouchEvent | MouseEvent) => void;
 	onSplitterClick: (event: MouseEvent) => void;
 	onSplitterDblClick: (_event: MouseEvent) => void;
+	/** A store that tells what is the previous pane size.
+	 *
+	 * If undefined, it means that you are the first pane.
+	 * Otherwise, it contains the details about the previous panel size details.
+	 */
+	previousPaneSizeStore: Readable<SizeDetails | undefined>;
 };
 
 // methods passed from splitpane to children panes
 export interface SplitContext {
-	/** Tells the key of the very first pane, or undefined if not recieved yet. */
-	veryFirstPaneKey: Readable<any>;
 	isHorizontal: Readable<boolean>;
 	showFirstSplitter: Readable<boolean>;
 	onPaneInit: PaneInitFunction;

src/lib/internal/store.ts

@@ -0,0 +1,51 @@
+import { readable, type Readable } from 'svelte/store';
+
+export interface SwitchableStoreResult<T> {
+	store: Readable<T>;
+	update: (store?: Readable<T>) => void;
+}
+
+export function switchableStore<T extends K, K>(
+	initialStore?: Readable<T> | undefined,
+	unsetValue: K = undefined
+): SwitchableStoreResult<T> {
+	let currentStore = initialStore;
+	let _set: ((value: T) => void) | undefined = undefined;
+	let unsubscribe: (() => void) | undefined = undefined;
+
+	function makeSubscription(store: Readable<T> | undefined, set: (value: T) => void) {
+		if (store) {
+			return store.subscribe((val) => {
+				set(val);
+			});
+		} else {
+			set(unsetValue as T);
+			return undefined;
+		}
+	}
+
+	const store = readable<T>(undefined as T, (set) => {
+		unsubscribe = makeSubscription(currentStore, set);
+		_set = set;
+
+		return () => {
+			if (unsubscribe) {
+				unsubscribe();
+			}
+			unsubscribe = undefined;
+			_set = undefined;
+		};
+	});
+
+	const update = (store?: Readable<T>) => {
+		currentStore = store;
+		if (_set) {
+			if (unsubscribe) {
+				unsubscribe();
+			}
+			unsubscribe = makeSubscription(currentStore, _set);
+		}
+	};
+
+	return { store, update };
+}