Function buttonClicked

examples/CairoUI/DemoWidgetClickable.hpp:113–120

    }

    void buttonClicked(SubWidget*, int) override
    {
        fColorId = (fColorId + 1) % 3;
        repaint();

        if (fCallback != nullptr)
            fCallback->demoWidgetClicked(this, fColorId);
    }

private:
    Callback* fCallback;