Refactor reload.js to allow saving only some state when reloading.

The reload state is now divided into 3 different components:
  pointer, narrow, compose

static/js/reload.js

@@ -13,13 +13,14 @@ exports.is_in_progress = function () {
     return reload_in_progress;
 };
 
-function preserve_state(send_after_reload) {
+function preserve_state(send_after_reload, save_pointer, save_narrow, save_compose) {
     if (send_after_reload === undefined) {
         send_after_reload = 0;
     }
     var url = "#reload:send_after_reload=" + Number(send_after_reload);
     url += "+csrf_token=" + encodeURIComponent(csrf_token);
 
+    if (save_compose) {
         if (compose.composing() === 'stream') {
             url += "+msg_type=stream";
             url += "+stream=" + encodeURIComponent(compose.stream_name());
@@ -32,11 +33,16 @@ function preserve_state(send_after_reload) {
         if (compose.composing()) {
             url += "+msg=" + encodeURIComponent(compose.message_content());
         }
+    }
 
+    if (save_pointer) {
         var pointer = home_msg_list.selected_id();
         if (pointer !== -1) {
             url += "+pointer=" + pointer;
         }
+    }
+
+    if (save_narrow) {
         var row = home_msg_list.selected_row();
         if (!narrow.active()) {
             if (row.length > 0) {
@@ -54,6 +60,7 @@ function preserve_state(send_after_reload) {
                 url += "+narrow_offset=" + narrow_row.offset().top;
             }
         }
+    }
 
     var oldhash = window.location.hash;
     if (oldhash.length !== 0 && oldhash[0] === '#') {
@@ -159,12 +166,12 @@ function cleanup_before_reload() {
     }
 }
 
-function do_reload_app(send_after_reload, save_state, message) {
+function do_reload_app(send_after_reload, save_pointer, save_narrow, save_compose, message) {
     if (reload_in_progress) { return; }
 
     // TODO: we should completely disable the UI here
-    if (save_state) {
-        preserve_state(send_after_reload);
+    if (save_pointer || save_narrow || save_compose) {
+        preserve_state(send_after_reload, save_pointer, save_narrow, save_compose);
     }
 
     if (message === undefined) {
@@ -186,12 +193,18 @@ function do_reload_app(send_after_reload, save_state, message) {
 exports.initiate = function (options) {
     options = _.defaults({}, options, {
         immediate: false,
-        save_state: true,
+        save_pointer: true,
+        save_narrow: true,
+        save_compose: true,
         send_after_reload: false
     });
 
     if (options.immediate) {
-        do_reload_app(options.send_after_reload, options.save_state, options.message);
+        do_reload_app(options.send_after_reload,
+                      options.save_pointer,
+                      options.save_narrow,
+                      options.save_compose,
+                      options.message);
     }
 
     if (reload_pending) {
@@ -209,7 +222,11 @@ exports.initiate = function (options) {
     var compose_done_handler, compose_started_handler;
 
     function reload_from_idle () {
-        do_reload_app(false, options.save_state, options.message);
+        do_reload_app(false,
+                      options.save_pointer,
+                      options.save_narrow,
+                      options.save_compose,
+                      options.message);
     }
 
     // Make sure we always do a reload eventually

static/js/server_events.js

@@ -287,7 +287,10 @@ function get_events(options) {
                     ($.parseJSON(xhr.responseText).msg.indexOf("too old") !== -1 ||
                      $.parseJSON(xhr.responseText).msg.indexOf("Bad event queue id") !== -1)) {
                     page_params.event_queue_expired = true;
-                    reload.initiate({immediate: true, save_state: false});
+                    reload.initiate({immediate: true,
+                                     save_pointer: false,
+                                     save_narrow: false,
+                                     save_compose: false});
                 }
 
                 if (error_type === 'abort') {

static/js/zulip.js

@@ -273,7 +273,10 @@ function fast_forward_pointer() {
                 furthest_read = data.max_message_id;
                 unconditionally_send_pointer_update().then(function () {
                     ui.change_tab_to('#home');
-                    reload.initiate({immediate: true, save_state: false});
+                    reload.initiate({immediate: true,
+                                     save_pointer: false,
+                                     save_narrow: false,
+                                     save_compose: false});
                 });
             });
         }