window: Show account switcher on loading and error pages

If there are any sessions

src/account_switcher/account_switcher_button.rs

@@ -6,7 +6,12 @@ use gtk::{
 };
 
 use super::AccountSwitcherPopover;
-use crate::{components::Avatar, session_list::SessionInfo, utils::BoundObjectWeakRef, Window};
+use crate::{
+    components::Avatar,
+    session_list::SessionInfo,
+    utils::{template_callbacks::TemplateCallbacks, BoundObjectWeakRef},
+    Window,
+};
 
 mod imp {
     use glib::subclass::InitializingObject;
@@ -30,6 +35,7 @@ mod imp {
             SessionInfo::static_type();
 
             Self::bind_template(klass);
+            TemplateCallbacks::bind_template_callbacks(klass);
         }
 
         fn instance_init(obj: &InitializingObject<Self>) {

src/account_switcher/account_switcher_button.ui

@@ -1,6 +1,15 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <interface>
   <template class="AccountSwitcherButton" parent="GtkToggleButton">
+    <binding name="visible">
+      <closure type="gboolean" function="invert_boolean">
+        <lookup name="is-empty" type="SessionList">
+          <lookup name="session-list" type="Window">
+            <lookup name="root">AccountSwitcherButton</lookup>
+          </lookup>
+        </lookup>
+      </closure>
+    </binding>
     <property name="tooltip-text" translatable="yes">Switch Accounts</property>
     <accessibility>
       <property name="label" translatable="yes">Switch Accounts</property>

src/error_page.ui

@@ -4,12 +4,15 @@
     <child>
       <object class="AdwToolbarView">
         <child type="top">
-          <object class="GtkHeaderBar">
+          <object class="AdwHeaderBar">
             <property name="title-widget">
               <object class="AdwWindowTitle">
                 <property name="title" translatable="yes">Error</property>
               </object>
             </property>
+            <child type="start">
+              <object class="AccountSwitcherButton"/>
+            </child>
           </object>
         </child>
         <property name="content">

src/window.rs

@@ -7,7 +7,7 @@ use ruma::RoomId;
 use tracing::{error, info, warn};
 
 use crate::{
-    account_switcher::AccountSwitcherPopover,
+    account_switcher::{AccountSwitcherButton, AccountSwitcherPopover},
     components::Spinner,
     error_page::ErrorPage,
     greeter::Greeter,
@@ -67,6 +67,8 @@ mod imp {
         type ParentType = adw::ApplicationWindow;
 
         fn class_init(klass: &mut Self::Class) {
+            AccountSwitcherButton::static_type();
+
             Self::bind_template(klass);
 
             klass.add_binding_action(

src/window.ui

@@ -17,7 +17,11 @@
                 <property name="child">
                   <object class="AdwToolbarView">
                     <child type="top">
-                      <object class="GtkHeaderBar"/>
+                      <object class="AdwHeaderBar">
+                        <child type="start">
+                          <object class="AccountSwitcherButton"/>
+                        </child>
+                      </object>
                     </child>
                     <property name="content">
                       <object class="GtkBox">