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building-with-existing-widgets.md

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Building with Existing Widgets

Modifying an Existing Widget

class Thin_button : public ox::Button {
   public:
    Thin_button(ox::Glyph_string title) : Button{std::move(title)}
    {
        using namespace ox::pipe;
        *this | fixed_height(1) | wallpaper(U'~') | bg(ox::Color::Red);
    }
};

Small modifications to existing Widgets can be made with public inheritance. In this example a Button is modified to have a height of one cell, a wallpaper of tildes, and a red background. The constructor is a good place to modify Widget properties, such as:

The pipe namespace is being used here, rather than direct member function calls.

Combining Widgets with Layouts

using namespace ox;

struct Settings_pane : layout::Vertical<> {
    Label& title          = this->make_child<Label>(U"Settings");
    HCheckbox_label& foo = this->make_child<HCheckbox_label>({U"Foo"});
    HCheckbox_label& bar = this->make_child<HCheckbox_label>({U"Bar"});
    Thin_button& baz      = this->make_child<Thin_button>(U"Baz");
    Confirm_button& reset = this->make_child<Confirm_button>(U"Reset");

    Settings_pane() { *this | pipe::fixed_width(16); }
};

struct App : layout::Horizontal<> {
    Settings_pane& settings      = this->make_child<Settings_pane>();
    Main_app_widget& main_widget = this->make_child<Main_app_widget>();
};

A Layout is a container for Widgets. The make_child template function will construct the given Widget type, forwarding any parameters to the constructor. It will append that object to the Layout's child vector and return a reference to the newly constructed object.

Layouts are parameterized on Widget type, so that it can only hold children of that type or sub-types of that type. The default is Widget, so the template parameter of layout::Vertical<>, above, is left empty. The parameterized type is the type that Layout::get_children() holds references to. make_child also has its template parameter defaulted to the Layout's template parameter.

Layouts can modify their children, just like in the Thin_button example above.

Layouts are Widgets, but they should not have to override any event handlers, if new event handlers are needed, then a new Layout type should be created.

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