throttle markdown preview

www/code/main.js

@@ -110,6 +110,10 @@ define([
                 return stringify(obj);
             };
 
+            var drawPreview = Cryptpad.throttle(function () {
+                DiffMd.apply(DiffMd.render(editor.getValue()), $preview);
+            }, 150);
+
             var onLocal = config.onLocal = function () {
                 if (initializing) { return; }
                 if (isHistoryMode) { return; }
@@ -117,7 +121,7 @@ define([
 
                 editor.save();
 
-                DiffMd.apply(DiffMd.render(editor.getValue()), $preview);
+                drawPreview();
 
                 var textValue = canonicalize(CodeMirror.$textarea.val());
                 var shjson = stringifyInner(textValue);
@@ -324,14 +328,13 @@ define([
                 var hjson = JSON.parse(shjson);
                 var remoteDoc = hjson.content;
 
-                DiffMd.apply(DiffMd.render(remoteDoc), $preview);
-
                 var highlightMode = hjson.highlightMode;
                 if (highlightMode && highlightMode !== APP.highlightMode) {
                     CodeMirror.setMode(highlightMode, onModeChanged);
                 }
 
                 CodeMirror.setValueAndCursor(oldDoc, remoteDoc, TextPatcher);
+                drawPreview();
 
                 if (!readOnly) {
                     var textValue = canonicalize(CodeMirror.$textarea.val());

www/common/common-util.js

@@ -122,5 +122,14 @@ define([], function () {
         xhr.send(null);
     };
 
+    Util.throttle = function (f, ms) {
+        var to;
+        var g = function () {
+            window.clearTimeout(to);
+            to = window.setTimeout(f, ms);
+        };
+        return g;
+    };
+
     return Util;
 });

www/common/cryptpad-common.js

@@ -71,6 +71,7 @@ define([
     common.bytesToMegabytes = Util.bytesToMegabytes;
     common.bytesToKilobytes = Util.bytesToKilobytes;
     common.fetch = Util.fetch;
+    common.throttle = Util.throttle;
 
     // import hash utilities for export
     var createRandomHash = common.createRandomHash = Hash.createRandomHash;