Siv3D custom titlebar & close button

siv3d_custom_titlebar.cpp

#include <Siv3D.hpp>

class Titlebar
{
public:
    Titlebar(
        const int height = 24,
        const int margin = 2,
        const Color color = Palette::Mediumorchid,
        const Color fontColor = Palette::White,
        const Color shadowColor = Palette::Black)
        : height_(height), margin_(margin), color_(color), fontColor_(fontColor), shadowColor_(shadowColor), grab_(),
        font_(11, Typeface::Heavy, FontStyle::Bold)
    {
    }

    // * call every frame *
    void update()
    {
        const RectF bar = region();

        // d&d move window
        if (bar.leftPressed && !grab_) {
            grab_ = Mouse::Pos();
        }

        if (grab_) {
            if (!Input::MouseL.pressed) {
                grab_ = none;
            }
            else {
                Window::SetPos(Mouse::ScreenPos().movedBy(-grab_.value()));
            }
        }
    }

    void draw()
    {
        const RectF bar = region();

        bar.draw(color_);

        // highlight
        if (grab_) {
            bar.draw({ 0U,0U,0U,32U });
        }
        else if (bar.mouseOver) {
            bar.draw({ 255U,255U,255U,32U });
        }

        font_(Window::GetTitle()).drawCenter(bar.center.movedBy(2, 2), shadowColor_);
        font_(Window::GetTitle()).drawCenter(bar.center, fontColor_);
    }

    const RectF region()
    {
        return RectF(Window::Size().x - margin_ * 2, height_).movedBy(margin_, margin_);
    }

private:
    int height_;
    int margin_;
    Color color_;
    Color fontColor_;
    Color shadowColor_;
    Optional<Point> grab_;
    Font font_;
};

class CloseButton
{
public:
    CloseButton(const Vec2 pos, const int buttonSize = 24, const double crossSize = 8.0, const double crossWidth = 3.0)
        : pos_(pos), buttonSize_(buttonSize), crossSize_(crossSize), crossWidth_(crossWidth)
    {
    }

    const bool clicked()
    {
        return region().leftClicked;
    }

    void draw()
    {
        const RectF button = region();

        Polygon polyCross = Geometry2D::CreatePlus(8, 3.0).rotated(45_deg);
        polyCross.movedBy(button.center).draw(Palette::Indigo);

        // highlight
        if (button.mouseOver) {
            button.draw({ 255U,255U,255U, 64U + 32U * ((System::FrameCount() / 4) % 2) });
        }
    }

    const RectF region()
    {
        return RectF(buttonSize_).movedBy(pos_);
    }

private:
    Vec2 pos_;
    int buttonSize_;
    double crossSize_;
    double crossWidth_;
};

void Main()
{
    Window::SetStyle(WindowStyle::NonFrame);
    Window::Resize(640, 480);

    const int titlebarHeight = 24;
    const int titlebarMargin = 2;
    Titlebar titlebar(titlebarHeight, titlebarMargin);

    const int closebuttonSize = titlebarHeight;
    CloseButton closebutton(titlebar.region().tr.movedBy(-closebuttonSize, 0), closebuttonSize);

	while (System::Update())
    {
        if (closebutton.clicked()) {
            // quit app
            break;
        }

        titlebar.update();

        RectF(Window::Size()).draw(Palette::Black);  // draw bg

        titlebar.draw();
        
        closebutton.draw();
    }
}