utils: Add extension trait for reusing child widget

There would be less duplication if Rust allowed generic implementations
with different bounds. Oh well…

src/components/label_with_widgets.rs

@@ -338,3 +338,9 @@ impl LabelWithWidgets {
         self.imp().set_label_and_widgets(label, widgets);
     }
 }
+
+impl Default for LabelWithWidgets {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/components/loading/bin.rs

@@ -1,6 +1,8 @@
 use adw::prelude::*;
 use gtk::{glib, subclass::prelude::*, CompositeTemplate};
 
+use crate::utils::ChildPropertyExt;
+
 mod imp {
     use std::marker::PhantomData;
 
@@ -118,3 +120,13 @@ impl Default for LoadingBin {
         Self::new()
     }
 }
+
+impl ChildPropertyExt for LoadingBin {
+    fn child_property(&self) -> Option<gtk::Widget> {
+        self.child()
+    }
+
+    fn set_child_property(&self, child: Option<&impl IsA<gtk::Widget>>) {
+        self.set_child(child.map(Cast::upcast_ref));
+    }
+}

src/components/loading/button.rs

@@ -1,7 +1,8 @@
-use adw::subclass::prelude::*;
-use gtk::{glib, pango, prelude::*};
+use adw::{prelude::*, subclass::prelude::*};
+use gtk::{glib, pango};
 
 use super::LoadingBin;
+use crate::prelude::*;
 
 mod imp {
     use std::marker::PhantomData;
@@ -65,26 +66,22 @@ mod imp {
             }
             let obj = self.obj();
 
-            let child_label =
-                if let Some(child_label) = self.loading_bin.child().and_downcast::<gtk::Label>() {
-                    child_label
-                } else {
-                    let child_label = gtk::Label::builder()
-                        .ellipsize(pango::EllipsizeMode::End)
-                        .use_underline(true)
-                        .mnemonic_widget(&*obj)
-                        .css_classes(["text-button"])
-                        .build();
-
-                    self.loading_bin.set_child(Some(child_label.clone()));
-                    // In case it was an image before.
-                    obj.remove_css_class("image-button");
-                    obj.update_relation(&[gtk::accessible::Relation::LabelledBy(&[
-                        child_label.upcast_ref()
-                    ])]);
-
-                    child_label
-                };
+            let child_label = self.loading_bin.child_or_else::<gtk::Label>(|| {
+                let child_label = gtk::Label::builder()
+                    .ellipsize(pango::EllipsizeMode::End)
+                    .use_underline(true)
+                    .mnemonic_widget(&*obj)
+                    .css_classes(["text-button"])
+                    .build();
+
+                // In case it was an image before.
+                obj.remove_css_class("image-button");
+                obj.update_relation(&[gtk::accessible::Relation::LabelledBy(&[
+                    child_label.upcast_ref()
+                ])]);
+
+                child_label
+            });
 
             child_label.set_label(label);
 
@@ -106,19 +103,13 @@ mod imp {
             }
             let obj = self.obj();
 
-            let child_image =
-                if let Some(child_image) = self.loading_bin.child().and_downcast::<gtk::Image>() {
-                    child_image
-                } else {
-                    let child_image = gtk::Image::builder()
-                        .accessible_role(gtk::AccessibleRole::Presentation)
-                        .build();
-
-                    self.loading_bin.set_child(Some(child_image.clone()));
-                    obj.add_css_class("image-button");
+            let child_image = self.loading_bin.child_or_else::<gtk::Image>(|| {
+                obj.add_css_class("image-button");
 
-                    child_image
-                };
+                gtk::Image::builder()
+                    .accessible_role(gtk::AccessibleRole::Presentation)
+                    .build()
+            });
 
             child_image.set_icon_name(Some(icon_name));
 

src/components/media/content_viewer.rs

@@ -230,14 +230,7 @@ mod imp {
 
         /// View the given location as a geo URI.
         pub(super) fn view_location(&self, geo_uri: &GeoUri) {
-            let location =
-                if let Some(location) = self.viewer.child().and_downcast::<LocationViewer>() {
-                    location
-                } else {
-                    let location = LocationViewer::new();
-                    self.viewer.set_child(Some(&location));
-                    location
-                };
+            let location = self.viewer.child_or_default::<LocationViewer>();
 
             location.set_location(geo_uri);
             self.update_animated_paintable_state();

src/components/media/location_viewer.rs

@@ -148,3 +148,9 @@ impl LocationViewer {
         self.imp().set_location(geo_uri);
     }
 }
+
+impl Default for LocationViewer {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/prelude.rs

@@ -10,6 +10,6 @@ pub(crate) use crate::{
     utils::{
         matrix::ext_traits::*,
         string::{StrExt, StrMutExt},
-        LocationExt,
+        ChildPropertyExt, IsABin, LocationExt,
     },
 };

src/session/view/content/explore/mod.rs

@@ -17,6 +17,7 @@ pub use self::{
 use self::{server::ExploreServer, server_list::ExploreServerList, server_row::ExploreServerRow};
 use crate::{
     components::LoadingRow,
+    prelude::*,
     session::model::Session,
     utils::{BoundObject, LoadingState, SingleItemListModel},
 };
@@ -122,16 +123,7 @@ mod imp {
                 };
 
                 if let Some(public_room) = item.downcast_ref::<PublicRoom>() {
-                    let public_room_row = if let Some(public_room_row) =
-                        list_item.child().and_downcast::<PublicRoomRow>()
-                    {
-                        public_room_row
-                    } else {
-                        let public_room_row = PublicRoomRow::new();
-                        list_item.set_child(Some(&public_room_row));
-                        public_room_row
-                    };
-
+                    let public_room_row = list_item.child_or_default::<PublicRoomRow>();
                     public_room_row.set_public_room(public_room);
                 } else if let Some(loading_row) = item.downcast_ref::<LoadingRow>() {
                     list_item.set_child(Some(loading_row));

src/session/view/content/explore/public_room_row.rs

@@ -240,3 +240,9 @@ impl PublicRoomRow {
         glib::Object::new()
     }
 }
+
+impl Default for PublicRoomRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/content/room_details/history_viewer/audio.rs

@@ -5,6 +5,7 @@ use tracing::error;
 use super::{AudioRow, HistoryViewerEvent, HistoryViewerEventType, HistoryViewerTimeline};
 use crate::{
     components::LoadingRow,
+    prelude::*,
     spawn,
     utils::{BoundConstructOnlyObject, LoadingState},
 };
@@ -86,16 +87,7 @@ mod imp {
 
                     list_item.set_child(Some(loading_row));
                 } else if let Some(event) = item.and_downcast::<HistoryViewerEvent>() {
-                    let audio_row =
-                        if let Some(audio_row) = list_item.child().and_downcast::<AudioRow>() {
-                            audio_row
-                        } else {
-                            let audio_row = AudioRow::new();
-                            list_item.set_child(Some(&audio_row));
-
-                            audio_row
-                        };
-
+                    let audio_row = list_item.child_or_default::<AudioRow>();
                     audio_row.set_event(Some(event));
                 }
             });

src/session/view/content/room_details/history_viewer/audio_row.rs

@@ -191,3 +191,9 @@ impl AudioRow {
         glib::Object::new()
     }
 }
+
+impl Default for AudioRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/content/room_details/history_viewer/file.rs

@@ -5,6 +5,7 @@ use tracing::error;
 use super::{FileRow, HistoryViewerEvent, HistoryViewerEventType, HistoryViewerTimeline};
 use crate::{
     components::LoadingRow,
+    prelude::*,
     spawn,
     utils::{BoundConstructOnlyObject, LoadingState},
 };
@@ -86,16 +87,7 @@ mod imp {
 
                     list_item.set_child(Some(loading_row));
                 } else if let Some(event) = item.and_downcast::<HistoryViewerEvent>() {
-                    let file_row =
-                        if let Some(file_row) = list_item.child().and_downcast::<FileRow>() {
-                            file_row
-                        } else {
-                            let file_row = FileRow::new();
-                            list_item.set_child(Some(&file_row));
-
-                            file_row
-                        };
-
+                    let file_row = list_item.child_or_default::<FileRow>();
                     file_row.set_event(Some(event));
                 }
             });

src/session/view/content/room_details/history_viewer/file_row.rs

@@ -177,3 +177,9 @@ impl FileRow {
         glib::Object::new()
     }
 }
+
+impl Default for FileRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/content/room_details/history_viewer/visual_media.rs

@@ -5,6 +5,7 @@ use tracing::error;
 use super::{HistoryViewerEvent, HistoryViewerEventType, HistoryViewerTimeline, VisualMediaItem};
 use crate::{
     components::LoadingRow,
+    prelude::*,
     session::view::MediaViewer,
     spawn,
     utils::{BoundConstructOnlyObject, LoadingState},
@@ -91,20 +92,7 @@ mod imp {
 
                     list_item.set_child(Some(loading_row));
                 } else if let Some(event) = item.and_downcast::<HistoryViewerEvent>() {
-                    let media_item = if let Some(media_item) =
-                        list_item.child().and_downcast::<VisualMediaItem>()
-                    {
-                        media_item
-                    } else {
-                        let media_item = VisualMediaItem::new();
-                        media_item.set_width_request(SIZE_REQUEST);
-                        media_item.set_height_request(SIZE_REQUEST);
-
-                        list_item.set_child(Some(&media_item));
-
-                        media_item
-                    };
-
+                    let media_item = list_item.child_or_default::<VisualMediaItem>();
                     media_item.set_event(Some(event));
                 }
             });

src/session/view/content/room_details/history_viewer/visual_media_item.rs

@@ -241,3 +241,9 @@ impl VisualMediaItem {
         glib::Object::new()
     }
 }
+
+impl Default for VisualMediaItem {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/content/room_details/history_viewer/visual_media_item.ui

@@ -3,6 +3,8 @@
   <template class="ContentVisualMediaHistoryViewerItem" parent="GtkWidget">
     <property name="focusable">True</property>
     <property name="accessible-role">button</property>
+    <property name="height-request">150</property>
+    <property name="width-request">150</property>
     <child>
       <object class="GtkGestureClick">
         <signal name="released" handler="activate" swapped="true"/>

src/session/view/content/room_details/members_page/members_list_view/item_row.rs

@@ -2,9 +2,12 @@ use adw::{prelude::*, subclass::prelude::*};
 use gtk::glib;
 
 use super::MembershipSubpageRow;
-use crate::session::{
-    model::Member,
-    view::content::room_details::{MemberRow, MembershipSubpageItem},
+use crate::{
+    prelude::*,
+    session::{
+        model::Member,
+        view::content::room_details::{MemberRow, MembershipSubpageItem},
+    },
 };
 
 mod imp {
@@ -50,26 +53,15 @@ mod imp {
 
             if let Some(item) = &item {
                 if let Some(member) = item.downcast_ref::<Member>() {
-                    let child = if let Some(child) = obj.child().and_downcast::<MemberRow>() {
-                        child
-                    } else {
-                        let child = MemberRow::new(true);
-                        obj.set_child(Some(&child));
-                        child
-                    };
+                    let child = obj.child_or_else::<MemberRow>(|| MemberRow::new(true));
                     child.set_member(Some(member.clone()));
                     self.set_activatable(true);
                 } else if let Some(item) = item.downcast_ref::<MembershipSubpageItem>() {
-                    let child =
-                        if let Some(child) = obj.child().and_downcast::<MembershipSubpageRow>() {
-                            child
-                        } else {
-                            let child = MembershipSubpageRow::new();
-                            child.set_activatable(false);
-
-                            obj.set_child(Some(&child));
-                            child
-                        };
+                    let child = obj.child_or_else::<MembershipSubpageRow>(|| {
+                        let child = MembershipSubpageRow::new();
+                        child.set_activatable(false);
+                        child
+                    });
 
                     child.set_item(Some(item.clone()));
                     self.set_activatable(true);
@@ -108,3 +100,5 @@ impl ItemRow {
         glib::Object::new()
     }
 }
+
+impl IsABin for ItemRow {}

src/session/view/content/room_history/divider_row.rs

@@ -139,3 +139,9 @@ impl DividerRow {
         glib::Object::new()
     }
 }
+
+impl Default for DividerRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/content/room_history/event_row.rs

@@ -292,22 +292,10 @@ mod imp {
             let obj = self.obj();
 
             if event.is_state_event() {
-                let child = if let Some(child) = obj.child().and_downcast::<StateRow>() {
-                    child
-                } else {
-                    let child = StateRow::new();
-                    obj.set_child(Some(&child));
-                    child
-                };
+                let child = obj.child_or_default::<StateRow>();
                 child.set_event(event);
             } else {
-                let child = if let Some(child) = obj.child().and_downcast::<MessageRow>() {
-                    child
-                } else {
-                    let child = MessageRow::new();
-                    obj.set_child(Some(&child));
-                    child
-                };
+                let child = obj.child_or_default::<MessageRow>();
                 child.set_event(event);
             }
         }
@@ -365,3 +353,13 @@ impl EventRow {
             .build()
     }
 }
+
+impl ChildPropertyExt for EventRow {
+    fn child_property(&self) -> Option<gtk::Widget> {
+        self.child()
+    }
+
+    fn set_child_property(&self, child: Option<&impl IsA<gtk::Widget>>) {
+        self.set_child(child);
+    }
+}

src/session/view/content/room_history/message_row/caption.rs

@@ -2,7 +2,7 @@ use gtk::{glib, prelude::*, subclass::prelude::*};
 use ruma::events::room::message::FormattedBody;
 
 use super::{text::MessageText, ContentFormat};
-use crate::session::model::Room;
+use crate::{prelude::*, session::model::Room};
 
 mod imp {
     use std::marker::PhantomData;
@@ -121,3 +121,13 @@ impl Default for MessageCaption {
         Self::new()
     }
 }
+
+impl ChildPropertyExt for MessageCaption {
+    fn child_property(&self) -> Option<gtk::Widget> {
+        self.child()
+    }
+
+    fn set_child_property(&self, child: Option<&impl IsA<gtk::Widget>>) {
+        self.set_child(child.map(Cast::upcast_ref));
+    }
+}

src/session/view/content/room_history/message_row/content.rs

@@ -216,28 +216,10 @@ impl MessageContent {
     }
 }
 
-/// Helper trait for types used to build a message's content.
-trait MessageContentContainer: IsA<gtk::Widget> {
-    /// Get the child of this widget
-    fn child(&self) -> Option<gtk::Widget>;
-
-    /// Set the child of this widget
-    fn set_child(&self, child: Option<gtk::Widget>);
-
-    /// Reuse the child of this widget if it is of the correct type `W`, or
-    /// replace it with a new `W` constructed with its `Default` implementation.
-    ///
-    /// Returns the reused or new widget.
-    fn reuse_child_or_default<W: IsA<gtk::Widget> + Clone + Default>(&self) -> W {
-        if let Some(child) = self.child().and_downcast::<W>() {
-            child
-        } else {
-            let child = W::default();
-            self.set_child(Some(child.clone().upcast()));
-            child
-        }
-    }
+impl IsABin for MessageContent {}
 
+/// Helper trait for types used to build a message's content.
+trait MessageContentContainer: ChildPropertyExt {
     /// Build the content widget of `event` as a child of this widget.
     fn build_content(
         &self,
@@ -279,7 +261,7 @@ trait MessageContentContainer: IsA<gtk::Widget> {
                     );
                 }
                 MsgLikeKind::UnableToDecrypt(_) => {
-                    let child = self.reuse_child_or_default::<MessageText>();
+                    let child = self.child_or_default::<MessageText>();
                     child.with_plain_text(gettext("Could not decrypt this message, decryption will be retried once the keys are available."), format);
                 }
                 msg_like_kind => {
@@ -296,7 +278,7 @@ trait MessageContentContainer: IsA<gtk::Widget> {
 
     /// Build the widget of an unsupported content as a child of this widget.
     fn build_unsupported_content(&self, format: ContentFormat) {
-        let child = self.reuse_child_or_default::<MessageText>();
+        let child = self.child_or_default::<MessageText>();
         child.with_plain_text(gettext("Unsupported event"), format);
     }
 
@@ -324,7 +306,7 @@ trait MessageContentContainer: IsA<gtk::Widget> {
 
         match msgtype {
             MessageType::Emote(message) => {
-                let child = self.reuse_child_or_default::<MessageText>();
+                let child = self.child_or_default::<MessageText>();
                 child.with_emote(
                     message.formatted.clone(),
                     message.body.clone(),
@@ -335,11 +317,11 @@ trait MessageContentContainer: IsA<gtk::Widget> {
                 );
             }
             MessageType::Location(message) => {
-                let child = self.reuse_child_or_default::<MessageLocation>();
+                let child = self.child_or_default::<MessageLocation>();
                 child.set_geo_uri(&message.geo_uri, format);
             }
             MessageType::Notice(message) => {
-                let child = self.reuse_child_or_default::<MessageText>();
+                let child = self.child_or_default::<MessageText>();
                 child.with_markup(
                     message.formatted.clone(),
                     message.body.clone(),
@@ -349,11 +331,11 @@ trait MessageContentContainer: IsA<gtk::Widget> {
                 );
             }
             MessageType::ServerNotice(message) => {
-                let child = self.reuse_child_or_default::<MessageText>();
+                let child = self.child_or_default::<MessageText>();
                 child.with_plain_text(message.body.clone(), format);
             }
             MessageType::Text(message) => {
-                let child = self.reuse_child_or_default::<MessageText>();
+                let child = self.child_or_default::<MessageText>();
                 child.with_markup(
                     message.formatted.clone(),
                     message.body.clone(),
@@ -364,7 +346,7 @@ trait MessageContentContainer: IsA<gtk::Widget> {
             }
             msgtype => {
                 warn!("Event not supported: {msgtype:?}");
-                let child = self.reuse_child_or_default::<MessageText>();
+                let child = self.child_or_default::<MessageText>();
                 child.with_plain_text(gettext("Unsupported event"), format);
             }
         }
@@ -381,7 +363,7 @@ trait MessageContentContainer: IsA<gtk::Widget> {
         cache_key: MessageCacheKey,
     ) {
         if let Some((caption, formatted_caption)) = media_message.caption() {
-            let caption_widget = self.reuse_child_or_default::<MessageCaption>();
+            let caption_widget = self.child_or_default::<MessageCaption>();
 
             caption_widget.set_caption(
                 caption.to_owned(),
@@ -413,54 +395,35 @@ trait MessageContentContainer: IsA<gtk::Widget> {
                 let Some(session) = room.session() else {
                     return;
                 };
-                let widget = self.reuse_child_or_default::<MessageAudio>();
+                let widget = self.child_or_default::<MessageAudio>();
                 widget.audio(audio.into(), &session, format, cache_key);
             }
             MediaMessage::File(file) => {
-                let widget = self.reuse_child_or_default::<MessageFile>();
+                let widget = self.child_or_default::<MessageFile>();
 
                 let media_message = MediaMessage::from(file);
                 widget.set_filename(Some(media_message.filename()));
                 widget.set_format(format);
             }
             MediaMessage::Image(image) => {
-                let widget = self.reuse_child_or_default::<MessageVisualMedia>();
+                let widget = self.child_or_default::<MessageVisualMedia>();
                 widget.set_media_message(image.into(), room, format, cache_key);
             }
             MediaMessage::Video(video) => {
-                let widget = self.reuse_child_or_default::<MessageVisualMedia>();
+                let widget = self.child_or_default::<MessageVisualMedia>();
                 widget.set_media_message(video.into(), room, format, cache_key);
             }
             MediaMessage::Sticker(sticker) => {
-                let widget = self.reuse_child_or_default::<MessageVisualMedia>();
+                let widget = self.child_or_default::<MessageVisualMedia>();
                 widget.set_media_message(sticker.into(), room, format, cache_key);
             }
         }
     }
 }
 
-impl<W> MessageContentContainer for W
-where
-    W: IsA<adw::Bin> + IsA<gtk::Widget>,
-{
-    fn child(&self) -> Option<gtk::Widget> {
-        BinExt::child(self)
-    }
-
-    fn set_child(&self, child: Option<gtk::Widget>) {
-        BinExt::set_child(self, child.as_ref());
-    }
-}
+impl<W> MessageContentContainer for W where W: IsABin {}
 
-impl MessageContentContainer for MessageCaption {
-    fn child(&self) -> Option<gtk::Widget> {
-        self.child()
-    }
-
-    fn set_child(&self, child: Option<gtk::Widget>) {
-        self.set_child(child);
-    }
-}
+impl MessageContentContainer for MessageCaption {}
 
 /// The data used as a cache key for messages.
 ///

src/session/view/content/room_history/message_row/mod.rs

@@ -287,3 +287,9 @@ impl MessageRow {
         self.imp().texture()
     }
 }
+
+impl Default for MessageRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/content/room_history/message_row/text/mod.rs

@@ -214,13 +214,7 @@ mod imp {
         fn build_plain_text(&self, mut text: String) {
             let obj = self.obj();
 
-            let child = if let Some(child) = obj.child().and_downcast::<gtk::Label>() {
-                child
-            } else {
-                let child = new_message_label();
-                obj.set_child(Some(&child));
-                child
-            };
+            let child = obj.child_or_else::<gtk::Label>(new_message_label);
 
             if EMOJI_REGEX.is_match(&text) {
                 child.add_css_class("emoji-message");
@@ -279,13 +273,7 @@ mod imp {
             }
 
             let obj = self.obj();
-            let child = if let Some(child) = obj.child().and_downcast::<LabelWithWidgets>() {
-                child
-            } else {
-                let child = LabelWithWidgets::new();
-                obj.set_child(Some(&child));
-                child
-            };
+            let child = obj.child_or_default::<LabelWithWidgets>();
 
             child.set_ellipsize(ellipsize);
             child.set_use_markup(true);
@@ -449,6 +437,8 @@ impl Default for MessageText {
     }
 }
 
+impl IsABin for MessageText {}
+
 /// Whether the given [`FormattedBody`] contains HTML.
 fn formatted_body_is_html(formatted: &FormattedBody) -> bool {
     formatted.format == MessageFormat::Html && !formatted.body.contains("<!-- raw HTML omitted -->")

src/session/view/content/room_history/mod.rs

@@ -530,24 +530,12 @@ mod imp {
             };
 
             if let Some(event) = item.downcast_ref::<Event>() {
-                let child = if let Some(child) = list_item.child().and_downcast::<EventRow>() {
-                    child
-                } else {
-                    let child = EventRow::new(&self.obj());
-                    list_item.set_child(Some(&child));
-                    child
-                };
+                let child = list_item.child_or_else::<EventRow>(|| EventRow::new(&self.obj()));
                 child.set_event(Some(event.clone()));
             } else if let Some(virtual_item) = item.downcast_ref::<VirtualItem>() {
                 set_virtual_item_child(list_item, virtual_item);
             } else if let Some(group) = item.downcast_ref::<GroupingListGroup>() {
-                let child = if let Some(child) = list_item.child().and_downcast::<StateGroupRow>() {
-                    child
-                } else {
-                    let child = StateGroupRow::new();
-                    list_item.set_child(Some(&child));
-                    child
-                };
+                let child = list_item.child_or_default::<StateGroupRow>();
                 child.set_group(Some(group.clone()));
             } else {
                 error!("Could not build widget for unsupported room history item: {item:?}");
@@ -1167,27 +1155,14 @@ fn set_virtual_item_child(list_item: &gtk::ListItem, virtual_item: &VirtualItem)
             }
         }
         VirtualItemKind::Typing => {
-            let child = if let Some(child) = list_item.child().and_downcast::<TypingRow>() {
-                child
-            } else {
-                let child = TypingRow::new();
-                list_item.set_child(Some(&child));
-                child
-            };
-
+            let child = list_item.child_or_default::<TypingRow>();
             let typing_list = virtual_item.room().typing_list();
             child.set_list(Some(typing_list));
         }
         VirtualItemKind::TimelineStart
         | VirtualItemKind::DayDivider(_)
         | VirtualItemKind::NewMessages => {
-            let divider = if let Some(divider) = list_item.child().and_downcast::<DividerRow>() {
-                divider
-            } else {
-                let divider = DividerRow::new();
-                list_item.set_child(Some(&divider));
-                divider
-            };
+            let divider = list_item.child_or_default::<DividerRow>();
             divider.set_virtual_item(Some(virtual_item));
         }
     }

src/session/view/content/room_history/state/content.rs

@@ -1,6 +1,6 @@
 use adw::{prelude::*, subclass::prelude::*};
 use gettextrs::gettext;
-use gtk::glib;
+use gtk::{glib, pango};
 use matrix_sdk_ui::timeline::{
     AnyOtherFullStateEventContent, MemberProfileChange, MembershipChange, OtherState,
     RoomMembershipChange, TimelineItemContent,
@@ -105,11 +105,8 @@ mod imp {
             let obj = self.obj();
             match widget {
                 WidgetType::Text(message) => {
-                    if let Some(child) = obj.child().and_downcast::<gtk::Label>() {
-                        child.set_text(&message);
-                    } else {
-                        obj.set_child(Some(&text(&message)));
-                    }
+                    let child = obj.child_or_else::<gtk::Label>(text);
+                    child.set_label(&message);
                 }
                 WidgetType::Creation(widget) => obj.set_child(Some(&widget)),
                 WidgetType::Tombstone(widget) => obj.set_child(Some(&widget)),
@@ -223,12 +220,8 @@ mod imp {
                 }
             };
 
-            let obj = self.obj();
-            if let Some(child) = obj.child().and_downcast::<gtk::Label>() {
-                child.set_text(&message);
-            } else {
-                obj.set_child(Some(&text(&message)));
-            }
+            let child = self.obj().child_or_else::<gtk::Label>(text);
+            child.set_label(&message);
         }
 
         /// Convert a received membership change to a supported membership
@@ -349,12 +342,8 @@ mod imp {
                 gettext_f("{user} joined this room.", &[("user", display_name)])
             };
 
-            let obj = self.obj();
-            if let Some(child) = obj.child().and_downcast::<gtk::Label>() {
-                child.set_text(&message);
-            } else {
-                obj.set_child(Some(&text(&message)));
-            }
+            let child = self.obj().child_or_else::<gtk::Label>(text);
+            child.set_label(&message);
         }
     }
 }
@@ -377,18 +366,20 @@ impl Default for StateContent {
     }
 }
 
+impl IsABin for StateContent {}
+
 enum WidgetType {
     Text(String),
     Creation(StateCreation),
     Tombstone(StateTombstone),
 }
 
-/// Construct a `GtkLabel` for the given text.
-fn text(label: &str) -> gtk::Label {
-    let child = gtk::Label::new(Some(label));
-    child.set_css_classes(&["dimmed"]);
-    child.set_wrap(true);
-    child.set_wrap_mode(gtk::pango::WrapMode::WordChar);
-    child.set_xalign(0.0);
-    child
+/// Construct a `GtkLabel` for presenting a state content.
+fn text() -> gtk::Label {
+    gtk::Label::builder()
+        .css_classes(["dimmed"])
+        .wrap(true)
+        .wrap_mode(pango::WrapMode::WordChar)
+        .xalign(0.0)
+        .build()
 }

src/session/view/content/room_history/state/group_row.rs

@@ -246,3 +246,9 @@ impl StateGroupRow {
         glib::Object::new()
     }
 }
+
+impl Default for StateGroupRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/content/room_history/state/row.rs

@@ -56,3 +56,9 @@ impl StateRow {
         glib::Object::new()
     }
 }
+
+impl Default for StateRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/content/room_history/typing_row.rs

@@ -162,3 +162,9 @@ impl TypingRow {
         glib::Object::new()
     }
 }
+
+impl Default for TypingRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/sidebar/icon_item_row.rs

@@ -76,3 +76,9 @@ impl SidebarIconItemRow {
         glib::Object::new()
     }
 }
+
+impl Default for SidebarIconItemRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/sidebar/room_row.rs

@@ -298,3 +298,9 @@ impl SidebarRoomRow {
         glib::Object::new()
     }
 }
+
+impl Default for SidebarRoomRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/session/view/sidebar/row.rs

@@ -172,24 +172,14 @@ mod imp {
 
             if let Some(item) = item {
                 if let Some(section) = item.downcast_ref::<SidebarSection>() {
-                    let child = if let Some(child) = obj.child().and_downcast::<SidebarSectionRow>()
-                    {
-                        child
-                    } else {
+                    let child = obj.child_or_else::<SidebarSectionRow>(|| {
                         let child = SidebarSectionRow::new();
-                        obj.set_child(Some(&child));
                         obj.update_relation(&[Relation::LabelledBy(&[child.labelled_by()])]);
                         child
-                    };
+                    });
                     child.set_section(Some(section.clone()));
                 } else if let Some(room) = item.downcast_ref::<Room>() {
-                    let child = if let Some(child) = obj.child().and_downcast::<SidebarRoomRow>() {
-                        child
-                    } else {
-                        let child = SidebarRoomRow::new();
-                        obj.set_child(Some(&child));
-                        child
-                    };
+                    let child = obj.child_or_default::<SidebarRoomRow>();
 
                     let room_is_direct_handler = room.connect_is_direct_notify(clone!(
                         #[weak(rename_to = imp)]
@@ -222,26 +212,10 @@ mod imp {
 
                     child.set_room(Some(room.clone()));
                 } else if let Some(icon_item) = item.downcast_ref::<SidebarIconItem>() {
-                    let child =
-                        if let Some(child) = obj.child().and_downcast::<SidebarIconItemRow>() {
-                            child
-                        } else {
-                            let child = SidebarIconItemRow::new();
-                            obj.set_child(Some(&child));
-                            child
-                        };
-
+                    let child = obj.child_or_default::<SidebarIconItemRow>();
                     child.set_icon_item(Some(icon_item.clone()));
                 } else if let Some(verification) = item.downcast_ref::<IdentityVerification>() {
-                    let child =
-                        if let Some(child) = obj.child().and_downcast::<SidebarVerificationRow>() {
-                            child
-                        } else {
-                            let child = SidebarVerificationRow::new();
-                            obj.set_child(Some(&child));
-                            child
-                        };
-
+                    let child = obj.child_or_default::<SidebarVerificationRow>();
                     child.set_identity_verification(Some(verification.clone()));
                 } else {
                     panic!("Wrong row item: {item:?}");
@@ -810,3 +784,13 @@ impl SidebarRow {
         glib::Object::builder().property("sidebar", sidebar).build()
     }
 }
+
+impl ChildPropertyExt for SidebarRow {
+    fn child_property(&self) -> Option<gtk::Widget> {
+        self.child()
+    }
+
+    fn set_child_property(&self, child: Option<&impl IsA<gtk::Widget>>) {
+        self.set_child(child);
+    }
+}

src/session/view/sidebar/verification_row.rs

@@ -64,3 +64,9 @@ impl SidebarVerificationRow {
         glib::Object::new()
     }
 }
+
+impl Default for SidebarVerificationRow {
+    fn default() -> Self {
+        Self::new()
+    }
+}

src/utils/mod.rs

@@ -10,11 +10,12 @@ use std::{
     sync::{Arc, LazyLock},
 };
 
+use adw::prelude::*;
 use futures_util::{
     future::{self, Either, Future},
     pin_mut,
 };
-use gtk::{gio, glib, prelude::*};
+use gtk::{gio, glib};
 use regex::Regex;
 use tempfile::NamedTempFile;
 
@@ -634,3 +635,74 @@ impl Drop for CountedRef {
         }
     }
 }
+
+/// Extensions trait for types with a `child` property.
+pub(crate) trait ChildPropertyExt {
+    /// The child of this widget, is any.
+    fn child_property(&self) -> Option<gtk::Widget>;
+
+    /// Set the child of this widget.
+    fn set_child_property(&self, child: Option<&impl IsA<gtk::Widget>>);
+
+    /// Get the child if it is of the proper type, or construct it with the
+    /// given function and set is as the child of this widget before returning
+    /// it.
+    fn child_or_else<W>(&self, f: impl FnOnce() -> W) -> W
+    where
+        W: IsA<gtk::Widget>,
+    {
+        if let Some(child) = self.child_property().and_downcast() {
+            child
+        } else {
+            let child = f();
+            self.set_child_property(Some(&child));
+            child
+        }
+    }
+
+    /// Get the child if it is of the proper type, or construct it with its
+    /// `Default` implementation and set is as the child of this widget before
+    /// returning it.
+    fn child_or_default<W>(&self) -> W
+    where
+        W: IsA<gtk::Widget> + Default,
+    {
+        self.child_or_else(Default::default)
+    }
+}
+
+impl<W> ChildPropertyExt for W
+where
+    W: IsABin,
+{
+    fn child_property(&self) -> Option<gtk::Widget> {
+        self.child()
+    }
+
+    fn set_child_property(&self, child: Option<&impl IsA<gtk::Widget>>) {
+        self.set_child(child);
+    }
+}
+
+impl ChildPropertyExt for gtk::ListItem {
+    fn child_property(&self) -> Option<gtk::Widget> {
+        self.child()
+    }
+
+    fn set_child_property(&self, child: Option<&impl IsA<gtk::Widget>>) {
+        self.set_child(child);
+    }
+}
+
+/// Helper trait to implement for widgets that subclass `AdwBin`, to be able to
+/// use the `ChildPropertyExt` trait.
+///
+/// This trait is to circumvent conflicts in Rust's type system, where if we try
+/// to implement `ChildPropertyExt for W where W: IsA<adw::Bin>` it complains
+/// that the other external types that implement `ChildPropertyExt` might
+/// implement `IsA<adw::Bin>` in the future… So instead of reimplementing
+/// `ChildPropertyExt` for every type where we need it, which requires to
+/// implement two methods, we only implement this which requires nothing.
+pub(crate) trait IsABin: IsA<adw::Bin> {}
+
+impl IsABin for adw::Bin {}