Preload photo on mouseover

app/js/lib/mtproto.js

@@ -2810,9 +2810,8 @@ factory('MtpApiFileManager', function (MtpApiManager, $q, $window) {
             cacheFileWriter = fileWriter;
             // console.time(fileName + ' ' + (size / 1024));
 
-            // var limit = size > 102400 ? 65536 : 4096;
-            var limit = size > 30400 ? 524288 : 4096;
-            // var limit = size > 30400 ? 50480 : 4096;
+            var limit = 524288;
+            // var limit = size > 16384 ? 524288 : 51200;
             var writeFilePromise = $q.when(),
                 writeFileDeferred;
             for (var offset = 0; offset < size; offset += limit) {

app/js/services.js

@@ -1880,6 +1880,31 @@ angular.module('myApp.services', [])
     return photo;
   }
 
+  function preloadPhoto (photoID) {
+    if (!photos[photoID]) {
+      return;
+    }
+    var photo = photos[photoID],
+        fullWidth = $(window).width() - 36,
+        fullHeight = $($window).height() - 150,
+        fullPhotoSize = choosePhotoSize(photo, fullWidth, fullHeight);
+
+    if (fullPhotoSize && !fullPhotoSize.preloaded) {
+      fullPhotoSize.preloaded = true;
+      if (fullPhotoSize.size) {
+        MtpApiFileManager.downloadFile(fullPhotoSize.location.dc_id, {
+          _: 'inputFileLocation',
+          volume_id: fullPhotoSize.location.volume_id,
+          local_id: fullPhotoSize.location.local_id,
+          secret: fullPhotoSize.location.secret
+        }, fullPhotoSize.size);
+      } else {
+        MtpApiFileManager.downloadSmallFile(fullPhotoSize.location);
+      }
+    }
+  };
+  $rootScope.preloadPhoto = preloadPhoto;
+
   function wrapForFull (photoID) {
     var photo = wrapForHistory(photoID),
         fullWidth = $(window).width() - 36,
@@ -1940,6 +1965,7 @@ angular.module('myApp.services', [])
 
   return {
     savePhoto: savePhoto,
+    preloadPhoto: preloadPhoto,
     wrapForHistory: wrapForHistory,
     wrapForFull: wrapForFull,
     openPhoto: openPhoto

app/partials/message.html

@@ -96,7 +96,7 @@
 
         <div bo-if="historyMessage.media &amp;&amp; historyMessage.media._ != 'messageMediaEmpty'" class="im_message_media" ng-switch="historyMessage.media._">
 
-          <a ng-switch-when="messageMediaPhoto" class="im_message_photo_thumb" href="" ng-click="openPhoto(historyMessage.media.photo.id)" style="width: {{historyMessage.media.photo.thumb.width}}px;">
+          <a ng-switch-when="messageMediaPhoto" class="im_message_photo_thumb" href="" ng-click="openPhoto(historyMessage.media.photo.id)" style="width: {{historyMessage.media.photo.thumb.width}}px;" ng-mouseover="preloadPhoto(historyMessage.media.photo.id)">
             <img
               class="im_message_photo_thumb"
               my-load-thumb