LibGUI+VisualBuilder: Support custom editing widgets for property values.

Implemented this by letting GAbstractViews provide a GModelEditingDelegate
for a given index, which then knows how to create and setup a custom widget
appropriate for the data type being edited.

LibGUI/GAbstractView.cpp

@@ -1,6 +1,7 @@
 #include <Kernel/KeyCode.h>
 #include <LibGUI/GAbstractView.h>
 #include <LibGUI/GModel.h>
+#include <LibGUI/GModelEditingDelegate.h>
 #include <LibGUI/GPainter.h>
 #include <LibGUI/GScrollBar.h>
 #include <LibGUI/GTextBox.h>
@@ -71,15 +72,21 @@ void GAbstractView::begin_editing(const GModelIndex& index)
     if (m_edit_widget)
         delete m_edit_widget;
     m_edit_index = index;
-    m_edit_widget = new GTextBox(this);
+
+    ASSERT(aid_create_editing_delegate);
+    m_editing_delegate = aid_create_editing_delegate(index);
+    m_editing_delegate->bind(*model(), index);
+    m_editing_delegate->set_value(model()->data(index, GModel::Role::Display));
+    m_edit_widget = m_editing_delegate->widget();
+    add_child(*m_edit_widget);
     m_edit_widget->move_to_back();
-    m_edit_widget->set_text(model()->data(index, GModel::Role::Display).to_string());
     m_edit_widget_content_rect = content_rect(index).translated(frame_thickness(), frame_thickness());
     update_edit_widget_position();
     m_edit_widget->set_focus(true);
-    m_edit_widget->on_return_pressed = [this] {
+    m_editing_delegate->will_begin_editing();
+    m_editing_delegate->on_commit = [this] {
         ASSERT(model());
-        model()->set_data(m_edit_index, m_edit_widget->text());
+        model()->set_data(m_edit_index, m_editing_delegate->value());
         stop_editing();
     };
 }

LibGUI/GAbstractView.h

@@ -4,7 +4,7 @@
 #include <LibGUI/GModel.h>
 #include <LibGUI/GScrollableWidget.h>
 
-class GTextBox;
+class GModelEditingDelegate;
 
 class GAbstractView : public GScrollableWidget {
     friend class GModel;
@@ -35,6 +35,8 @@ public:
     Function<void(const GModelIndex&)> on_selection;
     Function<void(const GModelNotification&)> on_model_notification;
 
+    Function<OwnPtr<GModelEditingDelegate>(const GModelIndex&)> aid_create_editing_delegate;
+
     virtual const char* class_name() const override { return "GAbstractView"; }
 
 protected:
@@ -45,10 +47,11 @@ protected:
 
     bool m_editable { false };
     GModelIndex m_edit_index;
-    GTextBox* m_edit_widget { nullptr };
+    GWidget* m_edit_widget { nullptr };
     Rect m_edit_widget_content_rect;
 
 private:
     RefPtr<GModel> m_model;
+    OwnPtr<GModelEditingDelegate> m_editing_delegate;
     bool m_activates_on_selection { false };
 };

LibGUI/GComboBox.cpp

@@ -41,7 +41,11 @@ GComboBox::GComboBox(GWidget* parent)
         auto new_value = model()->data(index).to_string();
         m_editor->set_text(new_value);
         m_editor->select_all();
-        m_list_window->hide();
+        close();
+        deferred_invoke([this](auto&) {
+            if (on_change)
+                on_change(m_editor->text());
+        });
     };
 }
 
@@ -63,6 +67,11 @@ void GComboBox::set_model(NonnullRefPtr<GModel> model)
     m_list_view->set_model(move(model));
 }
 
+void GComboBox::select_all()
+{
+    m_editor->select_all();
+}
+
 void GComboBox::open()
 {
     if (!model())
@@ -100,3 +109,10 @@ void GComboBox::set_text(const String& text)
 {
     m_editor->set_text(text);
 }
+
+void GComboBox::set_only_allow_values_from_model(bool b)
+{
+    if (m_only_allow_values_from_model == b)
+        return;
+    m_editor->set_readonly(m_only_allow_values_from_model);
+}

LibGUI/GComboBox.h

@@ -16,11 +16,15 @@ public:
 
     void open();
     void close();
+    void select_all();
 
     GModel* model() { return m_list_view->model(); }
     const GModel* model() const { return m_list_view->model(); }
     void set_model(NonnullRefPtr<GModel>);
 
+    bool only_allow_values_from_model() const { return m_only_allow_values_from_model; }
+    void set_only_allow_values_from_model(bool);
+
     Function<void(const String&)> on_change;
     Function<void()> on_return_pressed;
 
@@ -34,4 +38,5 @@ private:
     GButton* m_open_button { nullptr };
     GWindow* m_list_window { nullptr };
     GListView* m_list_view { nullptr };
+    bool m_only_allow_values_from_model { false };
 };

LibGUI/GModelEditingDelegate.h

@@ -0,0 +1,60 @@
+#pragma once
+
+#include <LibGUI/GModel.h>
+#include <LibGUI/GTextBox.h>
+#include <LibGUI/GWidget.h>
+
+class GModelEditingDelegate {
+public:
+    GModelEditingDelegate() {}
+    virtual ~GModelEditingDelegate() {}
+
+    void bind(GModel& model, const GModelIndex& index)
+    {
+        if (m_model.ptr() == &model && m_index == index)
+            return;
+        m_model = model;
+        m_index = index;
+        m_widget = create_widget()->make_weak_ptr();
+    }
+
+    GWidget* widget() { return m_widget; }
+    const GWidget* widget() const { return m_widget; }
+
+    Function<void()> on_commit;
+
+    virtual GVariant value() const = 0;
+    virtual void set_value(const GVariant&) = 0;
+
+    virtual void will_begin_editing() { }
+
+protected:
+    virtual GWidget* create_widget() = 0;
+    void commit()
+    {
+        if (on_commit)
+            on_commit();
+    }
+
+private:
+    RefPtr<GModel> m_model;
+    GModelIndex m_index;
+    WeakPtr<GWidget> m_widget;
+};
+
+class GStringModelEditingDelegate : public GModelEditingDelegate {
+public:
+    GStringModelEditingDelegate() {}
+    virtual ~GStringModelEditingDelegate() override {}
+
+    virtual GWidget* create_widget() override
+    {
+        auto* textbox = new GTextBox(nullptr);
+        textbox->on_return_pressed = [this] {
+            commit();
+        };
+        return textbox;
+    }
+    virtual GVariant value() const override { return static_cast<const GTextBox*>(widget())->text(); }
+    virtual void set_value(const GVariant& value) override { static_cast<GTextBox*>(widget())->set_text(value.to_string()); }
+};