PaintBrush: Add move tool context menu with "move to back/front"

Tools can now have an in-image context menu which you get when right-
clicking inside the image editing area. Our first use of this is to
provide the ability to move layers to the back/front. :^)

Applications/PaintBrush/Image.cpp

@@ -79,4 +79,29 @@ GUI::Model& Image::layer_model()
     return *m_layer_model;
 }
 
+size_t Image::index_of(const Layer& layer) const
+{
+    for (size_t i = 0; i < m_layers.size(); ++i) {
+        if (&m_layers.at(i) == &layer)
+            return i;
+    }
+    ASSERT_NOT_REACHED();
+}
+
+void Image::move_layer_to_back(Layer& layer)
+{
+    NonnullRefPtr<Layer> protector(layer);
+    auto index = index_of(layer);
+    m_layers.remove(index);
+    m_layers.prepend(layer);
+}
+
+void Image::move_layer_to_front(Layer& layer)
+{
+    NonnullRefPtr<Layer> protector(layer);
+    auto index = index_of(layer);
+    m_layers.remove(index);
+    m_layers.append(layer);
+}
+
 }

Applications/PaintBrush/Image.h

@@ -55,9 +55,14 @@ public:
 
     GUI::Model& layer_model();
 
+    void move_layer_to_front(Layer&);
+    void move_layer_to_back(Layer&);
+
 private:
     explicit Image(const Gfx::Size&);
 
+    size_t index_of(const Layer&) const;
+
     Gfx::Size m_size;
     NonnullRefPtrVector<Layer> m_layers;
     RefPtr<GUI::Model> m_layer_model;

Applications/PaintBrush/ImageEditor.cpp

@@ -117,6 +117,13 @@ void ImageEditor::mouseup_event(GUI::MouseEvent& event)
     m_active_tool->on_mouseup(*m_active_layer, layer_event, event);
 }
 
+void ImageEditor::context_menu_event(GUI::ContextMenuEvent& event)
+{
+    if (!m_active_layer || !m_active_tool)
+        return;
+    m_active_tool->on_context_menu(*m_active_layer, event);
+}
+
 void ImageEditor::keydown_event(GUI::KeyEvent& event)
 {
     if (m_active_tool)

Applications/PaintBrush/ImageEditor.h

@@ -79,6 +79,7 @@ private:
     virtual void mouseup_event(GUI::MouseEvent&) override;
     virtual void keydown_event(GUI::KeyEvent&) override;
     virtual void keyup_event(GUI::KeyEvent&) override;
+    virtual void context_menu_event(GUI::ContextMenuEvent&) override;
 
     RefPtr<Image> m_image;
     RefPtr<Layer> m_active_layer;

Applications/PaintBrush/MoveTool.cpp

@@ -25,8 +25,11 @@
  */
 
 #include "MoveTool.h"
+#include "Image.h"
 #include "ImageEditor.h"
 #include "Layer.h"
+#include <LibGUI/Action.h>
+#include <LibGUI/Menu.h>
 #include <LibGUI/Window.h>
 #include <LibGfx/Bitmap.h>
 
@@ -101,4 +104,21 @@ void MoveTool::on_keydown(GUI::KeyEvent& event)
     m_editor->layers_did_change();
 }
 
+void MoveTool::on_context_menu(Layer& layer, GUI::ContextMenuEvent& event)
+{
+    if (!m_context_menu) {
+        m_context_menu = GUI::Menu::construct();
+        m_context_menu->add_action(GUI::CommonActions::make_move_to_front_action([this](auto&) {
+            m_editor->image()->move_layer_to_front(*m_context_menu_layer);
+            m_editor->layers_did_change();
+        }));
+        m_context_menu->add_action(GUI::CommonActions::make_move_to_back_action([this](auto&) {
+            m_editor->image()->move_layer_to_back(*m_context_menu_layer);
+            m_editor->layers_did_change();
+        }));
+    }
+    m_context_menu_layer = layer;
+    m_context_menu->popup(event.screen_position());
+}
+
 }

Applications/PaintBrush/MoveTool.h

@@ -39,6 +39,7 @@ public:
     virtual void on_mousemove(Layer&, GUI::MouseEvent& layer_event, GUI::MouseEvent& original_event) override;
     virtual void on_mouseup(Layer&, GUI::MouseEvent& layer_event, GUI::MouseEvent& original_event) override;
     virtual void on_keydown(GUI::KeyEvent&) override;
+    virtual void on_context_menu(Layer&, GUI::ContextMenuEvent&) override;
 
 private:
     virtual const char* class_name() const override { return "MoveTool"; }
@@ -47,6 +48,8 @@ private:
     RefPtr<Layer> m_layer_being_moved;
     Gfx::Point m_event_origin;
     Gfx::Point m_layer_origin;
+    RefPtr<GUI::Menu> m_context_menu;
+    RefPtr<Layer> m_context_menu_layer;
 };
 
 }

Applications/PaintBrush/Tool.h

@@ -43,6 +43,7 @@ public:
     virtual void on_mousedown(Layer&, GUI::MouseEvent&, GUI::MouseEvent&) {}
     virtual void on_mousemove(Layer&, GUI::MouseEvent&, GUI::MouseEvent&) {}
     virtual void on_mouseup(Layer&, GUI::MouseEvent&, GUI::MouseEvent&) {}
+    virtual void on_context_menu(Layer&, GUI::ContextMenuEvent&) {}
     virtual void on_tool_button_contextmenu(GUI::ContextMenuEvent&) {}
     virtual void on_second_paint(const Layer&, GUI::PaintEvent&) {}
     virtual void on_keydown(GUI::KeyEvent&) {}