diff --git a/DevTools/HackStudio/FormEditorWidget.h b/DevTools/HackStudio/FormEditorWidget.h
index 04758ab263..bfe557be33 100644
--- a/DevTools/HackStudio/FormEditorWidget.h
+++ b/DevTools/HackStudio/FormEditorWidget.h
@@ -23,6 +23,13 @@ public:
 
     class WidgetSelection {
     public:
+        Function<void(GWidget&)> on_remove;
+        Function<void(GWidget&)> on_add;
+        Function<void()> on_clear;
+
+        void enable_hooks() { m_hooks_enabled = true; }
+        void disable_hooks() { m_hooks_enabled = false; }
+
         bool is_empty() const
         {
             return m_widgets.is_empty();
@@ -51,16 +58,22 @@ public:
         {
             ASSERT(m_widgets.contains(&widget));
             m_widgets.remove(&widget);
+            if (m_hooks_enabled && on_remove)
+                on_remove(widget);
         }
 
         void add(GWidget& widget)
         {
             m_widgets.set(&widget);
+            if (m_hooks_enabled && on_add)
+                on_add(widget);
         }
 
         void clear()
         {
             m_widgets.clear();
+            if (m_hooks_enabled && on_clear)
+                on_clear();
         }
 
         template<typename Callback>
@@ -76,6 +89,7 @@ public:
 
     private:
         HashTable<GWidget*> m_widgets;
+        bool m_hooks_enabled { true };
     };
 
     WidgetSelection& selection() { return m_selection; }
diff --git a/DevTools/HackStudio/WidgetTreeModel.cpp b/DevTools/HackStudio/WidgetTreeModel.cpp
index a2740da185..130c666226 100644
--- a/DevTools/HackStudio/WidgetTreeModel.cpp
+++ b/DevTools/HackStudio/WidgetTreeModel.cpp
@@ -75,3 +75,14 @@ void WidgetTreeModel::update()
 {
     did_update();
 }
+
+GModelIndex WidgetTreeModel::index_for_widget(GWidget& widget) const
+{
+    int parent_child_index = 0;
+    for (auto& parent_child : widget.parent_widget()->child_widgets()) {
+        if (parent_child == &widget)
+            return create_index(parent_child_index, 0, &widget);
+        ++parent_child_index;
+    }
+    return {};
+}
diff --git a/DevTools/HackStudio/WidgetTreeModel.h b/DevTools/HackStudio/WidgetTreeModel.h
index 10a81da3fa..f7e784b9b6 100644
--- a/DevTools/HackStudio/WidgetTreeModel.h
+++ b/DevTools/HackStudio/WidgetTreeModel.h
@@ -15,6 +15,8 @@ public:
     virtual GModelIndex parent_index(const GModelIndex&) const override;
     virtual void update() override;
 
+    GModelIndex index_for_widget(GWidget&) const;
+
 private:
     explicit WidgetTreeModel(GWidget&);
 
diff --git a/DevTools/HackStudio/main.cpp b/DevTools/HackStudio/main.cpp
index e3f870d7d4..c18a7abcb1 100644
--- a/DevTools/HackStudio/main.cpp
+++ b/DevTools/HackStudio/main.cpp
@@ -100,7 +100,7 @@ int main(int argc, char** argv)
     Function<void()> update_actions;
 
     g_window = GWindow::construct();
-    g_window->set_rect(100, 100, 800, 600);
+    g_window->set_rect(90, 90, 840, 600);
     g_window->set_title("HackStudio");
 
     auto widget = GWidget::construct();
@@ -164,7 +164,7 @@ int main(int argc, char** argv)
 
     auto form_editing_pane_container = GSplitter::construct(Orientation::Vertical, form_editor_inner_splitter);
     form_editing_pane_container->set_size_policy(SizePolicy::Fixed, SizePolicy::Fill);
-    form_editing_pane_container->set_preferred_size(170, 0);
+    form_editing_pane_container->set_preferred_size(190, 0);
     form_editing_pane_container->set_layout(make<GBoxLayout>(Orientation::Vertical));
 
     auto add_properties_pane = [&](auto& text, auto pane_widget) {
@@ -181,6 +181,28 @@ int main(int argc, char** argv)
 
     auto form_widget_tree_view = GTreeView::construct(nullptr);
     form_widget_tree_view->set_model(g_form_editor_widget->model());
+    form_widget_tree_view->on_selection_change = [&] {
+        g_form_editor_widget->selection().disable_hooks();
+        g_form_editor_widget->selection().clear();
+        form_widget_tree_view->selection().for_each_index([&](auto& index) {
+            // NOTE: Make sure we don't add the FormWidget itself to the selection,
+            //       since that would allow you to drag-move the FormWidget.
+            if (index.internal_data() != &g_form_editor_widget->form_widget())
+                g_form_editor_widget->selection().add(*(GWidget*)index.internal_data());
+        });
+        g_form_editor_widget->update();
+        g_form_editor_widget->selection().enable_hooks();
+    };
+
+    g_form_editor_widget->selection().on_add = [&](auto& widget) {
+        form_widget_tree_view->selection().add(g_form_editor_widget->model().index_for_widget(widget));
+    };
+    g_form_editor_widget->selection().on_remove = [&](auto& widget) {
+        form_widget_tree_view->selection().remove(g_form_editor_widget->model().index_for_widget(widget));
+    };
+    g_form_editor_widget->selection().on_clear = [&] {
+        form_widget_tree_view->selection().clear();
+    };
 
     add_properties_pane("Form widget tree:", form_widget_tree_view);
     add_properties_pane("Widget properties:", GTableView::construct(nullptr));