Revert "Revert "Merge pull request #193 from matrix-org/rav/shouldComponentUpdates""

Put the shouldComponentUpdate methods back in, now that Matthew has stopped
demoing.

This reverts commit 606fdcb8df.

src/ObjectUtils.js

@@ -77,3 +77,34 @@ module.exports.getKeyValueArrayDiffs = function(before, after) {
 
     return results;
 };
+
+/**
+ * Shallow-compare two objects for equality: each key and value must be
+ * identical
+ */
+module.exports.shallowEqual = function(objA, objB) {
+    if (objA === objB) {
+        return true;
+    }
+
+    if (typeof objA !== 'object' || objA === null ||
+          typeof objB !== 'object' || objB === null) {
+        return false;
+    }
+
+    var keysA = Object.keys(objA);
+    var keysB = Object.keys(objB);
+
+    if (keysA.length !== keysB.length) {
+        return false;
+    }
+
+    for (var i = 0; i < keysA.length; i++) {
+        var key = keysA[i];
+        if (!objB.hasOwnProperty(key) || objA[key] !== objB[key]) {
+            return false;
+        }
+    }
+
+    return true;
+};

src/components/structures/RoomView.js

@@ -38,6 +38,7 @@ var SlashCommands = require("../../SlashCommands");
 var dis = require("../../dispatcher");
 var Tinter = require("../../Tinter");
 var rate_limited_func = require('../../ratelimitedfunc');
+var ObjectUtils = require('../../ObjectUtils');
 
 var DEBUG = false;
 
@@ -164,6 +165,11 @@ module.exports = React.createClass({
         }
     },
 
+    shouldComponentUpdate: function(nextProps, nextState) {
+        return (!ObjectUtils.shallowEqual(this.props, nextProps) ||
+                !ObjectUtils.shallowEqual(this.state, nextState));
+    },
+
     componentWillUnmount: function() {
         // set a boolean to say we've been unmounted, which any pending
         // promises can use to throw away their results.

src/components/structures/TimelinePanel.js

@@ -24,6 +24,7 @@ var EventTimeline = Matrix.EventTimeline;
 var sdk = require('../../index');
 var MatrixClientPeg = require("../../MatrixClientPeg");
 var dis = require("../../dispatcher");
+var ObjectUtils = require('../../ObjectUtils');
 
 var PAGINATE_SIZE = 20;
 var INITIAL_SIZE = 20;
@@ -146,6 +147,11 @@ var TimelinePanel = React.createClass({
         }
     },
 
+    shouldComponentUpdate: function(nextProps, nextState) {
+        return (!ObjectUtils.shallowEqual(this.props, nextProps) ||
+                !ObjectUtils.shallowEqual(this.state, nextState));
+    },
+
     componentWillUnmount: function() {
         // set a boolean to say we've been unmounted, which any pending
         // promises can use to throw away their results.