From 1c0496e051d8b1af297138732475b1689ada5eb8 Mon Sep 17 00:00:00 2001
From: Jason <jason.daurus@gmail.com>
Date: Thu, 10 Mar 2016 21:40:07 +0800
Subject: [web] VirtualScroll and AutoScroll helper

---
 web/src/js/components/helpers/AutoScroll.js | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 web/src/js/components/helpers/AutoScroll.js

(limited to 'web/src/js/components/helpers/AutoScroll.js')

diff --git a/web/src/js/components/helpers/AutoScroll.js b/web/src/js/components/helpers/AutoScroll.js
new file mode 100644
index 00000000..d37b9f37
--- /dev/null
+++ b/web/src/js/components/helpers/AutoScroll.js
@@ -0,0 +1,25 @@
+import React from "react";
+import ReactDOM from "react-dom";
+
+const symShouldStick = Symbol("shouldStick");
+const isAtBottom = v => v.scrollTop + v.clientHeight === v.scrollHeight;
+
+export default Component => Object.assign(class AutoScrollWrapper extends Component {
+
+    static displayName = Component.name;
+
+    componentWillUpdate() {
+        const viewport = ReactDOM.findDOMNode(this);
+        this[symShouldStick] = viewport.scrollTop && isAtBottom(viewport);
+        super.componentWillUpdate && super.componentWillUpdate();
+    }
+
+    componentDidUpdate() {
+        const viewport = ReactDOM.findDOMNode(this);
+        if (this[symShouldStick] && !isAtBottom(viewport)) {
+            viewport.scrollTop = viewport.scrollHeight;
+        }
+        super.componentDidUpdate && super.componentDidUpdate();
+    }
+
+}, Component);
-- 
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