text_widget.hpp

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// Copyright Take Vos 2021-2022.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "widget.hpp"
#include "text_delegate.hpp"
#include "../GUI/module.hpp"
#include "../text/module.hpp"
#include "../geometry/module.hpp"
#include "../l10n/module.hpp"
#include "../container/module.hpp"
#include "../observer/module.hpp"
#include "../scoped_task.hpp"
#include <memory>
#include <string>
#include <array>
#include <optional>
#include <future>
#include <limits>
#include <chrono>
 
namespace hi { inline namespace v1 {
 
template<typename Context>
concept text_widget_attribute = forward_of<Context, observer<hi::alignment>, observer<hi::semantic_text_style>>;
 
class text_widget final : public widget {
public:
    using super = widget;
    using delegate_type = text_delegate;
 
    std::shared_ptr<delegate_type> delegate;
 
    observer<alignment> alignment = hi::alignment::top_flush();
 
    observer<semantic_text_style> text_style = semantic_text_style::label;
 
    ~text_widget();
 
    text_widget(widget *parent, std::shared_ptr<delegate_type> delegate) noexcept;
 
    text_widget(widget *parent, std::shared_ptr<delegate_type> delegate, text_widget_attribute auto&&...attributes) noexcept :
        text_widget(parent, std::move(delegate))
    {
        set_attributes(hi_forward(attributes)...);
    }
 
    text_widget(
        widget *parent,
        different_from<std::shared_ptr<delegate_type>> auto&& text,
        text_widget_attribute auto&&...attributes) noexcept
        requires requires { make_default_text_delegate(hi_forward(text)); }
        : text_widget(parent, make_default_text_delegate(hi_forward(text)), hi_forward(attributes)...)
    {
    }
 
    [[nodiscard]] box_constraints update_constraints() noexcept override;
    void set_layout(widget_layout const& context) noexcept override;
    void draw(draw_context const& context) noexcept override;
    bool handle_event(gui_event const& event) noexcept override;
    hitbox hitbox_test(point2 position) const noexcept override;
    [[nodiscard]] bool accepts_keyboard_focus(keyboard_focus_group group) const noexcept override;
private:
    enum class add_type { append, insert, dead };
 
    struct undo_type {
        gstring text;
        text_selection selection;
    };
 
    enum class cursor_state_type { off, on, busy, none };
 
    gstring _text_cache;
    text_shaper _shaped_text;
 
    mutable box_constraints _constraints_cache;
 
    delegate_type::callback_token _delegate_cbt;
 
    decltype(text_style)::callback_token _text_style_cbt;
 
    text_selection _selection;
 
    scoped_task<> _blink_cursor;
 
    observer<cursor_state_type> _cursor_state = cursor_state_type::none;
    decltype(_cursor_state)::callback_token _cursor_state_cbt;
 
    bool _request_scroll = false;
 
    gui_event _last_drag_mouse_event = {};
 
    utc_nanoseconds _last_drag_mouse_event_next_repeat = {};
 
    float _vertical_movement_x = std::numeric_limits<float>::quiet_NaN();
 
    bool _overwrite_mode = false;
    
    std::optional<grapheme> _has_dead_character = std::nullopt;
 
    undo_stack<undo_type> _undo_stack = {1000};
 
    void set_attributes() noexcept {}
    void set_attributes(text_widget_attribute auto&& first, text_widget_attribute auto&&...rest) noexcept
    {
        if constexpr (forward_of<decltype(first), observer<hi::alignment>>) {
            alignment = hi_forward(first);
        } else if constexpr (forward_of<decltype(first), observer<hi::semantic_text_style>>) {
            text_style = hi_forward(first);
        } else {
            hi_static_no_default();
        }
 
        set_attributes(hi_forward(rest)...);
    }
 
    void scroll_to_show_selection() noexcept;
 
    void request_scroll() noexcept;
 
    void reset_state(char const *states) noexcept;
 
    [[nodiscard]] gstring_view selected_text() const noexcept;
    void undo_push() noexcept;
    void undo() noexcept;
    void redo() noexcept;
 
    scoped_task<> blink_cursor() noexcept;
 
    void fix_cursor_position() noexcept;
 
    void replace_selection(gstring const& replacement) noexcept;
 
    void add_character(grapheme c, add_type mode) noexcept;
    void delete_dead_character() noexcept;
    void delete_character_next() noexcept;
    void delete_character_prev() noexcept;
    void delete_word_next() noexcept;
    void delete_word_prev() noexcept;
};
 
}} // namespace hi::v1