Call `PopupMenu` min. size calculations after `about_to_popup` signal processing.

scene/gui/popup_menu.cpp

@@ -3211,21 +3211,24 @@ void PopupMenu::popup(const Rect2i &p_bounds) {
 		moved = Vector2();
 		popup_time_msec = OS::get_singleton()->get_ticks_msec();
 
-		Size2 scale = get_parent_viewport()->get_popup_base_transform().get_scale();
-		CanvasItem *c = Object::cast_to<CanvasItem>(get_parent());
-		if (c) {
-			scale *= c->get_global_transform_with_canvas().get_scale();
-		}
-		real_t popup_scale = MIN(scale.x, scale.y);
-		set_content_scale_factor(popup_scale);
-		Size2 minsize = get_contents_minimum_size() * popup_scale;
-		minsize.height = Math::ceil(minsize.height); // Ensures enough height at fractional content scales to prevent the v_scroll_bar from showing.
-		set_min_size(minsize); // `height` is truncated here by the cast to Size2i for Window.min_size.
-		set_size(Vector2(0, 0)); // Shrinkwraps to min size.
 		Popup::popup(p_bounds);
 	}
 }
 
+void PopupMenu::_pre_popup() {
+	Size2 scale = get_parent_viewport()->get_popup_base_transform().get_scale();
+	CanvasItem *c = Object::cast_to<CanvasItem>(get_parent());
+	if (c) {
+		scale *= c->get_global_transform_with_canvas().get_scale();
+	}
+	real_t popup_scale = MIN(scale.x, scale.y);
+	set_content_scale_factor(popup_scale);
+	Size2 minsize = get_contents_minimum_size() * popup_scale;
+	minsize.height = Math::ceil(minsize.height); // Ensures enough height at fractional content scales to prevent the v_scroll_bar from showing.
+	set_min_size(minsize); // `height` is truncated here by the cast to Size2i for Window.min_size.
+	reset_size(); // Shrinkwraps to min size.
+}
+
 void PopupMenu::set_visible(bool p_visible) {
 	bool native = global_menu.is_valid();
 #ifdef TOOLS_ENABLED

scene/gui/popup_menu.h

@@ -226,6 +226,7 @@ class PopupMenu : public Popup {
 	String _atr(int p_idx, const String &p_text) const;
 
 protected:
+	virtual void _pre_popup() override;
 	virtual Rect2i _popup_adjust_rect() const override;
 
 	virtual void add_child_notify(Node *p_child) override;

scene/main/window.cpp

@@ -1994,6 +1994,8 @@ void Window::popup(const Rect2i &p_screen_rect) {
 	ERR_MAIN_THREAD_GUARD;
 	emit_signal(SNAME("about_to_popup"));
 
+	_pre_popup();
+
 	if (!get_embedder() && get_flag(FLAG_POPUP)) {
 		// Send a focus-out notification when opening a Window Manager Popup.
 		SceneTree *scene_tree = get_tree();

scene/main/window.h

@@ -257,6 +257,7 @@ private:
 	static int root_layout_direction;
 
 protected:
+	virtual void _pre_popup() {} // Called after "about_to_popup", but before window is shown.
 	virtual Rect2i _popup_adjust_rect() const { return Rect2i(); }
 	virtual void _post_popup() {}