Make sure to allocate all children in allocate vfuncs

Clutter expects actors overriding the allocate vfunc to allocate all
mapped children of the actor, otherwise bad things happen.

So make sure we actually allocate all our visible children in our custom
allocation functions, and since we don't want to give them a real
allocation, just pass them an empty ClutterActorBox.

It would be nice if we had a way to hide children during the allocation
process where no relayout is queued like gtk allows with
gtk_widget_set_child_visible(), then we could avoid those weird empty
ClutterActorBoxes.

Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3098

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1481>

js/ui/search.js

@@ -422,10 +422,11 @@ var GridSearchResultsLayout = GObject.registerClass({
 
             const [childWidth] = child.get_preferred_width(-1);
             const [childHeight] = child.get_preferred_height(-1);
-            childBox.set_size(childWidth, childHeight);
 
-            if (childBox.x1 + childWidth > width)
+            if (childBox.x1 + childWidth <= width)
-                return;
+                childBox.set_size(childWidth, childHeight);
+            else
+                childBox.set_size(0, 0);
 
             child.allocate(childBox);
 

js/ui/userWidget.js

@@ -152,17 +152,21 @@ class UserWidgetLabel extends St.Widget {
 
         let [, , natRealNameWidth] = this._realNameLabel.get_preferred_size();
 
-        if (natRealNameWidth <= availWidth)
+        let childBox = new Clutter.ActorBox();
+
+        let hiddenLabel;
+        if (natRealNameWidth <= availWidth) {
             this._currentLabel = this._realNameLabel;
-        else
+            hiddenLabel = this._userNameLabel;
+        } else {
             this._currentLabel = this._userNameLabel;
+            hiddenLabel = this._realNameLabel;
+        }
         this.label_actor = this._currentLabel;
 
-        let childBox = new Clutter.ActorBox();
+        hiddenLabel.allocate(childBox);
-        childBox.x1 = 0;
+
-        childBox.y1 = 0;
+        childBox.set_size(availWidth, availHeight);
-        childBox.x2 = availWidth;
-        childBox.y2 = availHeight;
 
         this._currentLabel.allocate(childBox);
     }

js/ui/workspace.js

@@ -630,6 +630,14 @@ var WorkspaceLayout = GObject.registerClass({
 
             if (windowInfo.currentTransition) {
                 windowInfo.currentTransition.get_interval().set_final(childBox);
+
+                // The timeline of the transition might not have been updated
+                // before this allocation cycle, so make sure the child
+                // still updates needs_allocation to FALSE.
+                // Unfortunately, this relies on the fast paths in
+                // clutter_actor_allocate(), otherwise we'd start a new
+                // transition on the child, replacing the current one.
+                child.allocate(child.allocation);
                 continue;
             }
 

js/ui/workspaceThumbnail.js

@@ -1270,6 +1270,9 @@ var ThumbnailsBox = GObject.registerClass({
         let y = box.y1;
 
         if (this._dropPlaceholderPos == -1) {
+            this._dropPlaceholder.allocate_preferred_size(
+                ...this._dropPlaceholder.get_position());
+
             Meta.later_add(Meta.LaterType.BEFORE_REDRAW, () => {
                 this._dropPlaceholder.hide();
             });