frontend: Change 'reply' button label to reflect selected message.

The 'reply' button shows the stream>topic or recipient(s) of the
selected message, for better UX.  It also expands to fill the
remaining horizontal space in the button bar -- this should help make
it easier for new users to figure out how to reply.

Finally, it uses "Message" instead of "Reply", to better match the
compose box.

Fixes #17940.

frontend_tests/node_tests/compose_closed_ui.js

@@ -0,0 +1,88 @@
+"use strict";
+
+// Setup
+const {strict: assert} = require("assert");
+
+const {mock_cjs, mock_esm, set_global, zrequire} = require("../zjsunit/namespace");
+const {run_test} = require("../zjsunit/test");
+const $ = require("../zjsunit/zjquery");
+
+// Mocking and stubbing things
+mock_cjs("jquery", $);
+set_global("document", "document-stub");
+const message_lists = mock_esm("../../static/js/message_lists");
+
+// Code we're actually using/testing
+const compose_closed_ui = zrequire("compose_closed_ui");
+const {MessageList} = zrequire("message_list");
+
+// Helper test function
+function test_reply_label(expected_label) {
+    const label = $(".compose_reply_button_recipient_label").text();
+    assert.equal(label, expected_label, "'" + label + "' did not match '" + expected_label + "'");
+}
+
+run_test("reply_label", () => {
+    // Mocking up a test message list
+    const filter = {
+        predicate: () => () => true,
+    };
+    const list = new MessageList({
+        filter,
+    });
+    message_lists.current = list;
+    list.add_messages([
+        {
+            id: 0,
+            stream: "first_stream",
+            topic: "first_topic",
+        },
+        {
+            id: 1,
+            stream: "first_stream",
+            topic: "second_topic",
+        },
+        {
+            id: 2,
+            stream: "second_stream",
+            topic: "third_topic",
+        },
+        {
+            id: 3,
+            stream: "second_stream",
+            topic: "second_topic",
+        },
+        {
+            id: 4,
+            display_reply_to: "some user",
+        },
+        {
+            id: 5,
+            display_reply_to: "some user, other user",
+        },
+    ]);
+
+    const expected_labels = [
+        "#first_stream > first_topic",
+        "#first_stream > second_topic",
+        "#second_stream > third_topic",
+        "#second_stream > second_topic",
+        "some user",
+        "some user, other user",
+    ];
+
+    // Initialize the code we're testing.
+    compose_closed_ui.initialize();
+
+    // Run the tests!
+    let first = true;
+    for (const expected_label of expected_labels) {
+        if (first) {
+            list.select_id(list.first().id);
+            first = false;
+        } else {
+            list.select_id(list.next());
+        }
+        test_reply_label(expected_label);
+    }
+});

static/js/compose_closed_ui.js

@@ -0,0 +1,25 @@
+import $ from "jquery";
+
+import * as message_lists from "./message_lists";
+
+function update_reply_recipient_label() {
+    const message = message_lists.current.selected_message();
+    let recipient_label = "";
+    if (message) {
+        if (message.stream && message.topic) {
+            recipient_label = "#" + message.stream + " > " + message.topic;
+        } else if (message.display_reply_to) {
+            recipient_label = message.display_reply_to;
+        }
+    }
+    $(".compose_reply_button_recipient_label").text(recipient_label);
+}
+
+// TODO: Move the closed-compose buttons click handlers here, probably.
+
+export function initialize() {
+    // When the message selection changes, change the label on the Reply button.
+    $(document).on("message_selected.zulip", () => {
+        update_reply_recipient_label();
+    });
+}

static/js/ui_init.js

@@ -13,6 +13,7 @@ import * as blueslip from "./blueslip";
 import * as bot_data from "./bot_data";
 import * as click_handlers from "./click_handlers";
 import * as compose from "./compose";
+import * as compose_closed_ui from "./compose_closed_ui";
 import * as compose_pm_pill from "./compose_pm_pill";
 import * as composebox_typeahead from "./composebox_typeahead";
 import * as condense from "./condense";
@@ -470,6 +471,7 @@ export function initialize_everything() {
     scroll_bar.initialize();
     message_viewport.initialize();
     panels.initialize();
+    compose_closed_ui.initialize();
     initialize_kitchen_sink_stuff();
     echo.initialize();
     stream_edit.initialize();

static/styles/compose.css

@@ -1,13 +1,17 @@
 #compose_buttons {
     text-align: right;
+    display: flex;
+    flex-direction: row;
+    align-items: center;
 
     .new_message_button {
-        padding-top: 1.1em;
+        margin-left: 4px;
 
         .button.small {
             font-size: 1em;
             padding: 3px 10px;
             vertical-align: middle;
+            background-color: hsla(0, 0%, 0%, 0.1);
         }
 
         .compose_mobile_button {
@@ -16,10 +20,6 @@
                 font-weight: 400;
                 line-height: 1em;
             }
-
-            @media (width >= $sm_min) {
-                display: none;
-            }
         }
 
         .message-control-link {
@@ -29,27 +29,49 @@
         .alert-draft {
             font-size: 14px;
             color: hsl(170, 48%, 54%);
-            padding: 3px 12px;
+            padding: 0 12px;
             font-weight: 400;
             display: none;
         }
+    }
 
-        @media (width < $sm_min) {
+    .reply_button_container {
-            .compose_stream_button,
+        flex: 1;
-            .compose_private_button {
+        min-width: 0;
-                display: none;
+        margin-left: 0;
+
+        .compose_reply_button {
+            width: 100%;
+            text-align: left;
+            overflow: hidden;
+            white-space: nowrap;
+            text-overflow: ellipsis;
+
+            .compose_reply_button_recipient_label {
+                color: hsl(215, 47%, 30%);
             }
         }
     }
+
+    .mobile_button_container {
+        @media (width >= $sm_min) {
+            display: none;
+        }
+    }
+
+    .stream_button_container,
+    .private_button_container {
+        @media (width < $sm_min) {
+            display: none;
+        }
+    }
 }
 
 /* Main geometry for this element is in zulip.css */
 .compose-content {
     border-top: 1px solid hsla(0, 0%, 0%, 0.07);
     transition: background-color 200ms linear;
-
+    padding: 4px 4px 8px 4px;
-    padding: 8px 10px 8px 10px;
-
     border-left: 1px solid hsl(0, 0%, 93%);
     border-right: 1px solid hsl(0, 0%, 93%);
 }

static/styles/night_mode.css

@@ -32,6 +32,17 @@ body.night-mode {
         background-color: hsl(212, 28%, 18%);
     }
 
+    #compose_buttons .new_message_button .button.small {
+        background-color: hsla(0, 0%, 0%, 0.2);
+    }
+
+    #compose_buttons
+        .reply_button_container
+        .compose_reply_button
+        .compose_reply_button_recipient_label {
+        color: hsl(215, 47%, 80%);
+    }
+
     .compose-send-status-close {
         color: hsl(0, 0%, 100%);
         opacity: 1;

static/templates/compose.hbs

@@ -5,20 +5,32 @@
             <span id="compose-reply-error-msg"></span>
         </div>
         <div id="compose_buttons">
+            <span class="new_message_button reply_button_container">
+                <button type="button" class="button small rounded compose_reply_button"
+                  id="left_bar_compose_reply_button_big"
+                  title="{{t 'Reply' }} (r)">
+                    <span class="compose_reply_button_label">
+                        {{#tr}}
+                            Message <z-recipient></z-recipient>
+                            {{#*inline "z-recipient"}}<span class="compose_reply_button_recipient_label"></span>{{/inline}}
+                        {{/tr}}
+                    </span>
+                </button>
+            </span>
             <span class="new_message_button">
                 <a class="drafts-link no-underline button small rounded compose_drafts_button" href="#drafts" title="{{t 'Drafts' }} (d)">
                     {{t 'Drafts' }}
                 </a>
                 <span class="alert-draft pull-left">{{t 'Saved as draft' }}</span>
             </span>
-            <span class="new_message_button">
+            <span class="new_message_button mobile_button_container">
                 <button type="button" class="button small rounded compose_mobile_button"
                   id="left_bar_compose_mobile_button_big"
                   title="{{t 'New message' }} (c)">
                     <span>+</span>
                 </button>
             </span>
-            <span class="new_message_button">
+            <span class="new_message_button stream_button_container">
                 <button type="button" class="button small rounded compose_stream_button"
                   id="left_bar_compose_stream_button_big"
                   title="{{t 'New topic' }} (c)">
@@ -26,7 +38,7 @@
                 </button>
             </span>
             {{#unless embedded }}
-            <span class="new_message_button">
+            <span class="new_message_button private_button_container">
                 <button type="button" class="button small rounded compose_private_button"
                   id="left_bar_compose_private_button_big"
                   title="{{t 'New private message' }} (x)">
@@ -34,13 +46,6 @@
                 </button>
             </span>
             {{/unless}}
-            <span class="new_message_button">
-                <button type="button" class="button small rounded compose_reply_button"
-                  id="left_bar_compose_reply_button_big"
-                  title="{{t 'Reply' }} (r)">
-                    <span class="compose_reply_button_label">{{t 'Reply' }}</span>
-                </button>
-            </span>
         </div>
     </div>
     <div class="message_comp compose-content">