1 files changed, 62 insertions, 0 deletions
diff --git a/src/utils/react.ts b/src/utils/react.ts
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+++ b/src/utils/react.ts
@@ -0,0 +1,62 @@
+/*
+ * Vencord, a modification for Discord's desktop app
+ * Copyright (c) 2022 Vendicated and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+import { React } from "@webpack/common";
+
+import { checkIntersecting } from "./misc";
+
+/**
+ * Check if an element is on screen
+ * @param intersectOnly If `true`, will only update the state when the element comes into view
+ * @returns [refCallback, isIntersecting]
+ */
+export const useIntersection = (intersectOnly = false): [
+    refCallback: React.RefCallback<Element>,
+    isIntersecting: boolean,
+] => {
+    const observerRef = React.useRef<IntersectionObserver | null>(null);
+    const [isIntersecting, setIntersecting] = React.useState(false);
+
+    const refCallback = (element: Element | null) => {
+        observerRef.current?.disconnect();
+        observerRef.current = null;
+
+        if (!element) return;
+
+        if (checkIntersecting(element)) {
+            setIntersecting(true);
+            if (intersectOnly) return;
+        }
+
+        observerRef.current = new IntersectionObserver(entries => {
+            for (const entry of entries) {
+                if (entry.target !== element) continue;
+                if (entry.isIntersecting && intersectOnly) {
+                    setIntersecting(true);
+                    observerRef.current?.disconnect();
+                    observerRef.current = null;
+                } else {
+                    setIntersecting(entry.isIntersecting);
+                }
+            }
+        });
+        observerRef.current.observe(element);
+    };
+
+    return [refCallback, isIntersecting];
+};