Revert rendering window changes related to summarization

This reverts commit c10d9c1a0d23891acce88bf8d79866c08cb75681.
This reverts commit 9259a246946cd968a8725c38ff5ef2d4b4793717.

(imported from commit 50e9e0136c2487cc63d75ae2b78df0c70a1b0be1)

static/js/message_list.js

@@ -297,41 +297,6 @@ MessageList.prototype = {
         return null;
     },
 
-    // Counts the number of fully-displayed (not summarized, muted, or hidden)
-    // messages from array position idx1 to idx2
-    count_full_messages_between: function (idx1, idx2) {
-        var i;
-        var count = 0;
-        for (i = idx1; i < idx2; i++) {
-            if (this.summary_adjective(this._items[i]) === null) {
-                count += 1;
-            }
-        }
-        return count;
-    },
-
-    // Adjusts an array index backwards by `count` fully-displayed messages
-    idx_full_messages_before: function (idx, count) {
-        while (idx > 0 && count > 0){
-            idx -= 1;
-            if (this.summary_adjective(this._items[idx]) === null) {
-                count -= 1;
-            }
-        }
-        return idx;
-    },
-
-    // Advances an array index forward past `count` fully-displayed messages
-    idx_full_messages_after: function (idx, count) {
-        while (idx < this._items.length && count > 0){
-            if (this.summary_adjective(this._items[idx]) === null) {
-                count -= 1;
-            }
-            idx += 1;
-        }
-        return idx;
-    },
-
     selected_idx: function MessageList_selected_idx() {
         return util.lower_bound(this._items, this._selected_id,
                                 function (a, b) { return a.id < b; });

static/js/message_list_view.js

@@ -505,13 +505,14 @@ MessageListView.prototype = {
     },
 
     update_render_window: function MessageListView__update_render_window(selected_idx, check_for_changed) {
-        var new_start = this.list.idx_full_messages_before(selected_idx, this._RENDER_WINDOW_SIZE / 2);
+        var new_start = Math.max(selected_idx - this._RENDER_WINDOW_SIZE / 2, 0);
         if (check_for_changed && new_start === this._render_win_start) {
             return false;
         }
 
         this._render_win_start = new_start;
-        this._render_win_end = this.list.idx_full_messages_after(selected_idx, this._RENDER_WINDOW_SIZE / 2);
+        this._render_win_end = Math.min(this._render_win_start + this._RENDER_WINDOW_SIZE,
+                                        this.list.num_items());
         return true;
     },
 
@@ -524,15 +525,17 @@ MessageListView.prototype = {
         var selected_idx = this.list.selected_idx();
 
         // We rerender under the following conditions:
-        // * The selected message is within this._RENDER_THRESHOLD visible
+        // * The selected message is within this._RENDER_THRESHOLD messages
-        //   messages of the top of the currently rendered window and the top
+        //   of the top of the currently rendered window and the top
-        //   of the window does not abut the beginning of the message list
+        //   of the window does not abut the beginning of the message
-        // * The selected message is within this._RENDER_THRESHOLD visible
+        //   list
-        //   messages of the bottom of the currently rendered window and the
+        // * The selected message is within this._RENDER_THRESHOLD messages
-        //   bottom of the window does not abut the end of the message list
+        //   of the bottom of the currently rendered window and the
-        if (! (((this.list.count_full_messages_between(this._render_win_start, selected_idx) < this._RENDER_THRESHOLD)
+        //   bottom of the window does not abut the end of the
+        //   message list
+        if (! (((selected_idx - this._render_win_start < this._RENDER_THRESHOLD)
                 && (this._render_win_start !== 0)) ||
-               ((this.list.count_full_messages_between(selected_idx, this._render_win_end) <= this._RENDER_THRESHOLD)
+               ((this._render_win_end - selected_idx <= this._RENDER_THRESHOLD)
                 && (this._render_win_end !== this.list.num_items()))))
         {
             return false;
@@ -571,7 +574,7 @@ MessageListView.prototype = {
     },
 
     append: function MessageListView__append(messages, messages_are_new) {
-        var cur_window_size = this.list.count_full_messages_between(this._render_win_start, this._render_win_end);
+        var cur_window_size = this._render_win_end - this._render_win_start;
         if (cur_window_size < this._RENDER_WINDOW_SIZE) {
             var slice_to_render = messages.slice(0, this._RENDER_WINDOW_SIZE - cur_window_size);
             this.render(slice_to_render, 'bottom', messages_are_new);

zerver/tests/frontend/node/message_list.js

@@ -114,28 +114,3 @@ var MessageList = require('js/message_list');
     assert.equal(list.nth_most_recent_id(3), 10);
     assert.equal(list.nth_most_recent_id(4), -1);
 }());
-
-(function test_message_counting() {
-    global.feature_flags.summarize_read_while_narrowed = true;
-    var list = new MessageList(undefined, {}, {summarize_read: 'home'});
-
-    var summarized_flags = ['summarize_in_home'];
-    var unsummarized_flags = [];
-
-    list.append([
-        {id: 10, flags: unsummarized_flags},
-        {id: 20, flags: unsummarized_flags},
-        {id: 30, flags: summarized_flags},
-        {id: 40, flags: summarized_flags},
-        {id: 50, flags: unsummarized_flags},
-        {id: 60, flags: summarized_flags}
-    ]);
-    list.min_id_exempted_from_summaries = 10000;
-
-    assert.equal(list.count_full_messages_between(1, 5), 2);
-    assert.equal(list.idx_full_messages_before(5, 2), 1);
-    assert.equal(list.idx_full_messages_before(5, 10), 0);
-    assert.equal(list.idx_full_messages_after(0, 3), 5);
-    assert.equal(list.idx_full_messages_after(0, 10), 6);
-
-}());