From 1b5fb31b2c9936ebe0a8e0c46f7bf6d32f4f9d88 Mon Sep 17 00:00:00 2001
From: Zev Benjamin <zev@humbughq.com>
Date: Tue, 7 May 2013 11:15:20 -0400
Subject: [PATCH] Make viewport a module that caches height and width values

The .height() and .width() functions are actually pretty expensive for
the number of times we call them.  The viewport height and width
don't change often, though, so we can just cache them and recalculate
them on window resize.

(imported from commit 129fb8c058144125e2974f6b7967cd9f1a5c9ead)
---
 humbug/settings.py           |  1 +
 zephyr/static/js/viewport.js | 44 ++++++++++++++++++++++++++++++++++++
 zephyr/static/js/zephyr.js   |  2 --
 3 files changed, 45 insertions(+), 2 deletions(-)
 create mode 100644 zephyr/static/js/viewport.js

diff --git a/humbug/settings.py b/humbug/settings.py
index 613bf113ca..713d2b454c 100644
--- a/humbug/settings.py
+++ b/humbug/settings.py
@@ -281,6 +281,7 @@ PIPELINE_JS = {
             'js/blueslip.js',
             'js/util.js',
             'js/setup.js',
+            'js/viewport.js',
             'js/rows.js',
             'js/stream_list.js',
             'js/narrow.js',
diff --git a/zephyr/static/js/viewport.js b/zephyr/static/js/viewport.js
new file mode 100644
index 0000000000..9c9ed15b56
--- /dev/null
+++ b/zephyr/static/js/viewport.js
@@ -0,0 +1,44 @@
+var viewport = (function () {
+var exports = {};
+
+var jwindow;
+var height;
+var width;
+
+exports.scrollTop = function viewport_scrollTop () {
+    return jwindow.scrollTop.apply(jwindow, arguments);
+};
+
+exports.height = function viewport_height() {
+    if (arguments.length !== 0) {
+        height = undefined;
+        return jwindow.height.apply(jwindow, arguments);
+    }
+    if (height === undefined) {
+        height = $(window).height();
+    }
+    return height;
+};
+
+exports.width = function viewport_width() {
+    if (arguments.length !== 0) {
+        width = undefined;
+        return jwindow.width.apply(jwindow, arguments);
+    }
+    if (width === undefined) {
+        width = jwindow.width();
+    }
+    return width;
+};
+
+$(function () {
+    jwindow = $(window);
+    // This handler must be placed before all resize handlers in our application
+    jwindow.resize(function () {
+        height = undefined;
+        width = undefined;
+    });
+});
+
+return exports;
+}());
diff --git a/zephyr/static/js/zephyr.js b/zephyr/static/js/zephyr.js
index 57f3e1ad17..e8080eff2d 100644
--- a/zephyr/static/js/zephyr.js
+++ b/zephyr/static/js/zephyr.js
@@ -9,8 +9,6 @@ var recent_subjects = {};
 var queued_mark_as_read = [];
 var queued_flag_timer;
 
-var viewport = $(window);
-
 var get_updates_params = {
     pointer: -1
 };