Initial commit with files

Still need to fix the imports

src/lib/internal/ForcePortalRootContext.svelte

@@ -0,0 +1,17 @@
+<script lang="ts" context="module">
+    import { getContext, setContext } from "svelte";
+    import { writable, Writable } from "svelte/store";
+    const FORCE_PORTAL_ROOT_CONTEXT_NAME =
+        "headlessui-force-portal-root-context";
+
+    export function usePortalRoot(): Writable<boolean> | undefined {
+        return getContext(FORCE_PORTAL_ROOT_CONTEXT_NAME);
+    }
+</script>
+
+<script lang="ts">
+    export let force: boolean;
+    setContext(FORCE_PORTAL_ROOT_CONTEXT_NAME, writable(force));
+</script>
+
+<slot />

src/lib/internal/StackContextProvider.svelte

@@ -0,0 +1,42 @@
+<script lang="ts" context="module">
+    export enum StackMessage {
+        Add,
+        Remove,
+    }
+</script>
+
+<script lang="ts">
+    import { getContext, setContext } from "svelte";
+    import { writable, Writable } from "svelte/store";
+    type OnUpdate = (
+        message: StackMessage,
+        element: HTMLElement | null
+    ) => void;
+
+    export let onUpdate: OnUpdate | undefined;
+    export let element: HTMLElement | null;
+
+    let parentUpdateStore: Writable<OnUpdate> | undefined =
+        getContext("StackContext");
+    let notifyStore: Writable<OnUpdate> = writable(() => {});
+    setContext("StackContext", notifyStore);
+
+    $: notifyStore.set((...args: Parameters<OnUpdate>) => {
+        // Notify our layer
+        onUpdate?.(...args);
+
+        // Notify the parent
+        $parentUpdateStore?.(...args);
+    });
+
+    $: _cleanup = (() => {
+        if (_cleanup) {
+            _cleanup();
+        }
+        if (!element) return null;
+        $notifyStore(StackMessage.Add, element);
+        return () => $notifyStore(StackMessage.Remove, element);
+    })();
+</script>
+
+<slot />

src/lib/internal/dom-containers.ts

@@ -0,0 +1,7 @@
+export function contains(containers: Set<HTMLElement>, element: HTMLElement) {
+    for (let container of containers) {
+        if (container.contains(element)) return true
+    }
+
+    return false
+}

src/lib/internal/open-closed.ts

@@ -0,0 +1,21 @@
+import { getContext, setContext } from "svelte";
+import type { Writable } from "svelte/store";
+
+export enum State {
+    Open,
+    Closed,
+}
+
+const OPEN_CLOSED_CONTEXT_NAME = "OpenClosed";
+export function hasOpenClosed() {
+    return useOpenClosed() !== undefined
+}
+
+export function useOpenClosed(): Writable<State> | undefined {
+    return getContext(OPEN_CLOSED_CONTEXT_NAME);
+}
+
+export function useOpenClosedProvider(value: Writable<State>) {
+    setContext(OPEN_CLOSED_CONTEXT_NAME, value);
+}
+