Revert "Fix crash when conversation scrolled window child changes."

This reverts commit 07966a1156.

This commit was needed due to an issue in GTK
https://bugzilla.gnome.org/show_bug.cgi?id=778190 (which was later
migrated to https://gitlab.gnome.org/GNOME/gtk/-/issues/749).

This was fixed since 3.24.24, so bump the meson version too.

meson.build

@@ -54,7 +54,7 @@ valac = meson.get_compiler('vala')
 #
 
 target_glib = '2.68'
-target_gtk = '3.24.23'
+target_gtk = '3.24.24'
 target_vala = '0.48.18'
 target_webkit = '2.30'
 

src/client/conversation-viewer/conversation-viewer.vala

@@ -45,8 +45,7 @@ public class ConversationViewer : Gtk.Stack, Geary.BaseInterface {
     [GtkChild] private unowned Gtk.Grid empty_folder_page;
     [GtkChild] private unowned Gtk.Grid empty_search_page;
     [GtkChild] private unowned Gtk.Grid composer_page;
-
+    [GtkChild] private unowned Gtk.ScrolledWindow conversation_scroller;
-    private Gtk.ScrolledWindow conversation_scroller;
 
     [GtkChild] internal unowned Gtk.SearchBar conversation_find_bar;
 
@@ -144,9 +143,6 @@ public class ConversationViewer : Gtk.Stack, Geary.BaseInterface {
             this.conversation_find_entry
         );
 
-        // XXX GTK+ Bug 778190 workaround
-        new_conversation_scroller();
-
         // XXX Do this in Glade when possible.
         this.conversation_find_bar.connect_entry(this.conversation_find_entry);
     }
@@ -265,10 +261,7 @@ public class ConversationViewer : Gtk.Stack, Geary.BaseInterface {
                                         Application.ContactStore contacts,
                                         bool start_mark_timer)
         throws GLib.Error {
-        // Keep the old ScrolledWindow around long enough for its
+        var old_viewport = remove_current_list();
-        // descendant web views to be kept so their WebProcess can be
-        // re-used.
-        var old_scroller = remove_current_list();
 
         ConversationListBox new_list = new ConversationListBox(
             conversation,
@@ -312,9 +305,7 @@ public class ConversationViewer : Gtk.Stack, Geary.BaseInterface {
         }
 
         yield new_list.load_conversation(scroll_to, query);
-
+        old_viewport = null;
-        // Not strictly necessary, but keeps the compiler happy
-        old_scroller.destroy();
     }
 
     // Add a new conversation list to the UI
@@ -334,46 +325,23 @@ public class ConversationViewer : Gtk.Stack, Geary.BaseInterface {
     }
 
     // Remove any existing conversation list, cancelling its loading
-    private Gtk.ScrolledWindow remove_current_list() {
+    private Gtk.Widget remove_current_list() {
-        if (this.find_cancellable != null) {
+        // Remove the viewport that contains the current list
-            this.find_cancellable.cancel();
+        Gtk.Widget? scrolled_child = this.conversation_scroller.get_child();
-            this.find_cancellable = null;
+        if (scrolled_child != null) {
+            conversation_scroller.remove(scrolled_child);
         }
 
+        // Reset the scrollbars to their initial positions
+        this.conversation_scroller.hadjustment.set_value(0);
+        this.conversation_scroller.vadjustment.set_value(0);
+
         if (this.current_list != null) {
             this.current_list.cancel_conversation_load();
             this.conversation_removed(this.current_list);
             this.current_list = null;
         }
-
+        return scrolled_child;
-        var old_scroller = this.conversation_scroller;
-        // XXX GTK+ Bug 778190 workaround
-        this.conversation_page.remove(old_scroller);
-        new_conversation_scroller();
-        return old_scroller;
-    }
-
-    private void new_conversation_scroller() {
-        // XXX Work around for GTK+ Bug 778190: Instead of replacing
-        // the Viewport that contains the current list, replace the
-        // complete ScrolledWindow. Need to remove this method and
-        // put the settings back into conversation-viewer.ui when we
-        // can rely on it being fixed again.
-        Gtk.ScrolledWindow scroller = new Gtk.ScrolledWindow(null, null);
-        scroller.get_style_context().add_class("geary-conversation-scroller");
-        scroller.hscrollbar_policy = Gtk.PolicyType.NEVER;
-        scroller.set_hexpand(true);
-        scroller.set_vexpand(true);
-        scroller.show();
-        scroller.scroll_event.connect(
-            on_conversation_scroll
-        );
-        scroller.get_vscrollbar().button_release_event.connect(
-            on_conversation_scroll
-        );
-        this.conversation_scroller = scroller;
-        this.conversation_page.add(scroller);
-
     }
 
     /**
@@ -502,6 +470,7 @@ public class ConversationViewer : Gtk.Stack, Geary.BaseInterface {
         }
     }
 
+    [GtkCallback]
     private bool on_conversation_scroll() {
         if (this.current_list != null) {
             this.current_list.mark_visible_read();

ui/conversation-viewer.ui

@@ -35,6 +35,7 @@
       <object class="GtkGrid" id="conversation_page">
         <property name="visible">True</property>
         <property name="orientation">vertical</property>
+        <property name="can_focus">False</property>
         <child>
           <object class="GtkSearchBar" id="conversation_find_bar">
             <property name="visible">True</property>
@@ -109,7 +110,24 @@
           </packing>
         </child>
         <child>
-          <placeholder/>
+          <object class="GtkScrolledWindow" id="conversation_scroller">
+            <property name="visible">True</property>
+            <property name="can_focus">True</property>
+            <property name="hexpand">True</property>
+            <property name="vexpand">True</property>
+            <property name="hscrollbar_policy">never</property>
+            <signal name="scroll-event" handler="on_conversation_scroll" swapped="no"/>
+            <child>
+              <placeholder/>
+            </child>
+            <style>
+              <class name=".geary-conversation-scroller"/>
+            </style>
+          </object>
+          <packing>
+            <property name="left_attach">0</property>
+            <property name="top_attach">1</property>
+          </packing>
         </child>
       </object>
       <packing>