text_field_widget.hpp

// Copyright Take Vos 2021.
// 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 "text_field_delegate.hpp"
#include "widget.hpp"
#include "../text/editable_text.hpp"
#include "../format.hpp"
#include "../label.hpp"
#include <memory>
#include <string>
#include <array>
#include <optional>
#include <future>
 
namespace tt {
 
template<typename T>
class text_field_widget final : public widget {
public:
    using value_type = T;
    using delegate_type = text_field_delegate<value_type>;
    using super = widget;
 
    observable<value_type> value;
 
    template<typename Value = observable<value_type>>
    text_field_widget(
        gui_window &window,
        std::shared_ptr<abstract_container_widget> parent,
        std::weak_ptr<delegate_type> delegate,
        Value &&value = {}) noexcept :
        super(window, parent),
        value(std::forward<Value>(value)),
        _delegate(delegate),
        _field(theme::global->labelStyle),
        _shaped_text()
    {
        _value_callback = this->value.subscribe([this](auto...) {
            ttlet lock = std::scoped_lock(gui_system_mutex);
            _request_relayout = true;
        });
    }
 
    template<typename Value = observable<value_type>>
    text_field_widget(gui_window &window, std::shared_ptr<abstract_container_widget> parent, Value &&value = {}) noexcept :
        text_field_widget(window, parent, text_field_delegate_default<value_type>(), std::forward<Value>(value))
    {
    }
 
    ~text_field_widget() {}
 
    void set_delegate(std::weak_ptr<delegate_type> &&delegate) noexcept
    {
        ttlet lock = std::scoped_lock(gui_system_mutex);
        _delegate = delegate;
    }
 
    void set_continues(bool flag) noexcept
    {
        ttlet lock = std::scoped_lock(gui_system_mutex);
        _continues = flag;
    }
 
    [[nodiscard]] bool update_constraints(hires_utc_clock::time_point display_time_point, bool need_reconstrain) noexcept override
    {
        tt_axiom(gui_system_mutex.recurse_lock_count());
 
        if (super::update_constraints(display_time_point, need_reconstrain)) {
            ttlet text_style = theme::global->labelStyle;
            ttlet text_font_id = font_book::global->find_font(text_style.family_id, text_style.variant);
            ttlet &text_font = font_book::global->get_font(text_font_id);
            ttlet text_digit_width = text_font.description.DigitWidth * text_style.scaled_size();
 
            if (auto delegate = _delegate.lock()) {
                _text_width = std::ceil(text_digit_width * narrow_cast<float>(delegate->text_width(*this)));
            } else {
                _text_width = 100.0;
            }
 
            _preferred_size = {
                extent2{_text_width + theme::global->margin * 2.0f, theme::global->smallSize + theme::global->margin * 2.0f},
                extent2{std::numeric_limits<float>::infinity(), theme::global->smallSize + theme::global->margin * 2.0f}};
            _width_resistance = 2;
 
            return true;
        } else {
            return false;
        }
    }
 
    void update_layout(hires_utc_clock::time_point display_time_point, bool need_layout) noexcept override
    {
        tt_axiom(gui_system_mutex.recurse_lock_count());
 
        if (_focus && display_time_point >= _next_redraw_time_point) {
            request_redraw();
        }
 
        need_layout |= std::exchange(_request_relayout, false);
        if (need_layout) {
            _text_field_rectangle = aarectangle{extent2{_text_width + theme::global->margin * 2.0f, _size.height()}};
 
            // Set the clipping rectangle to within the border of the input field.
            // Add another border width, so glyphs do not touch the border.
            _text_field_clipping_rectangle = intersect(_clipping_rectangle, _text_field_rectangle);
 
            _text_rectangle = shrink(_text_field_rectangle, theme::global->margin);
 
            ttlet field_str = static_cast<std::string>(_field);
 
            if (auto delegate = _delegate.lock()) {
                if (_focus) {
                    // Update the optional error value from the string conversion when the
                    // field has keyboard focus.
                    delegate->from_string(*this, field_str, _error);
 
                } else {
                    // When field is not focused, simply follow the observed_value.
                    _field = delegate->to_string(*this, *value);
                    _error = {};
                }
 
            } else {
                _field = {};
                _error = l10n("system error: delegate missing");
            }
 
            _field.setStyleOfAll(theme::global->labelStyle);
            _field.setWidth(std::numeric_limits<float>::infinity());
            _shaped_text = _field.shapedText();
 
            // Record the last time the text is modified, so that the caret remains lit.
            _last_update_time_point = display_time_point;
        }
 
        super::update_layout(display_time_point, need_layout);
    }
 
    void draw(draw_context context, hires_utc_clock::time_point display_time_point) noexcept override
    {
        tt_axiom(gui_system_mutex.recurse_lock_count());
 
        _next_redraw_time_point = display_time_point + _blink_interval;
 
        if (overlaps(context, this->_clipping_rectangle)) {
            scroll_text();
 
            draw_background_box(context);
 
            // After drawing the border around the input field make sure any other
            // drawing remains inside this border. And change the transform to account
            // for how much the text has scrolled.
            context.set_clipping_rectangle(_text_field_clipping_rectangle);
            draw_selection_rectangles(context);
            draw_partial_grapheme_caret(context);
            draw_caret(context, display_time_point);
            draw_text(context);
        }
 
        super::draw(std::move(context), display_time_point);
    }
 
    bool handle_event(command command) noexcept override
    {
        ttlet lock = std::scoped_lock(gui_system_mutex);
        _request_relayout = true;
 
        if (*enabled) {
            switch (command) {
            case command::text_edit_paste:
                _field.handlePaste(window.get_text_from_clipboard());
                commit(false);
                return true;
 
            case command::text_edit_copy: window.set_text_on_clipboard(_field.handleCopy()); return true;
 
            case command::text_edit_cut: window.set_text_on_clipboard(_field.handleCut()); return true;
 
            case command::gui_escape: revert(true); return true;
 
            case command::gui_enter:
                commit(true);
                this->window.update_keyboard_target(
                    this->shared_from_this(), keyboard_focus_group::normal, keyboard_focus_direction::forward);
                return true;
 
            case command::gui_keyboard_enter:
                revert(true);
                // More processing of the gui_keyboard_enter command is required.
                break;
 
            case command::gui_keyboard_exit:
                commit(true);
                // More processing of the gui_keyboard_exit command is required.
                break;
 
            default:
                if (_field.handle_event(command)) {
                    commit(false);
                    return true;
                }
            }
        }
 
        return super::handle_event(command);
    }
 
    bool handle_event(mouse_event const &event) noexcept override
    {
        ttlet lock = std::scoped_lock(gui_system_mutex);
        auto handled = super::handle_event(event);
 
        // Make sure we only scroll when dragging outside the widget.
        _drag_scroll_speed_x = 0.0f;
        _drag_click_count = event.clickCount;
        _drag_select_position = event.position;
 
        if (event.cause.leftButton) {
            handled = true;
 
            if (!*enabled) {
                return true;
            }
 
            switch (event.type) {
                using enum mouse_event::Type;
            case ButtonDown:
                if (_text_rectangle.contains(event.position)) {
                    ttlet mouseInTextPosition = _text_inv_translate * event.position;
 
                    switch (event.clickCount) {
                    case 1:
                        if (event.down.shiftKey) {
                            _field.dragmouse_cursorAtCoordinate(mouseInTextPosition);
                        } else {
                            _field.setmouse_cursorAtCoordinate(mouseInTextPosition);
                        }
                        break;
                    case 2: _field.selectWordAtCoordinate(mouseInTextPosition); break;
                    case 3: _field.selectParagraphAtCoordinate(mouseInTextPosition); break;
                    default:;
                    }
 
                    // Record the last time the cursor is moved, so that the caret remains lit.
                    _last_update_time_point = event.timePoint;
 
                    request_redraw();
                }
                break;
 
            case Drag:
                // When the mouse is dragged beyond the line input,
                // start scrolling the text and select on the edge of the textRectangle.
                if (event.position.x() > _text_rectangle.right()) {
                    // The mouse is on the right of the text.
                    _drag_select_position.x() = _text_rectangle.right();
 
                    // Scroll text to the left in points per second.
                    _drag_scroll_speed_x = 50.0f;
 
                } else if (event.position.x() < _text_rectangle.left()) {
                    // The mouse is on the left of the text.
                    _drag_select_position.x() = _text_rectangle.left();
 
                    // Scroll text to the right in points per second.
                    _drag_scroll_speed_x = -50.0f;
                }
 
                drag_select();
 
                request_redraw();
                break;
 
            default:;
            }
        }
        return handled;
    }
 
    bool handle_event(keyboard_event const &event) noexcept override
    {
        ttlet lock = std::scoped_lock(gui_system_mutex);
 
        auto handled = super::handle_event(event);
 
        if (*enabled) {
            switch (event.type) {
                using enum keyboard_event::Type;
 
            case grapheme:
                handled = true;
                _field.insertgrapheme(event.grapheme);
                commit(false);
                break;
 
            case Partialgrapheme:
                handled = true;
                _field.insertPartialgrapheme(event.grapheme);
                commit(false);
                break;
 
            default:;
            }
        }
 
        _request_relayout = true;
        return handled;
    }
 
    hit_box hitbox_test(point2 position) const noexcept override
    {
        tt_axiom(gui_system_mutex.recurse_lock_count());
 
        if (_visible_rectangle.contains(position)) {
            return hit_box{weak_from_this(), _draw_layer, *enabled ? hit_box::Type::TextEdit : hit_box::Type::Default};
        } else {
            return hit_box{};
        }
    }
 
    [[nodiscard]] bool accepts_keyboard_focus(keyboard_focus_group group) const noexcept override
    {
        tt_axiom(gui_system_mutex.recurse_lock_count());
        return is_normal(group) && *enabled;
    }
 
    [[nodiscard]] color focus_color() const noexcept override
    {
        if (*enabled && window.active && _error) {
            return theme::global->errorLabelStyle.color;
        } else {
            return super::focus_color();
        }
    }
 
private:
    typename decltype(value)::callback_ptr_type _value_callback;
 
    std::weak_ptr<delegate_type> _delegate;
 
    bool _continues = false;
 
    l10n _error;
 
    float _text_width = 0.0f;
    aarectangle _text_rectangle = {};
 
    aarectangle _text_field_rectangle;
    aarectangle _text_field_clipping_rectangle;
 
    editable_text _field;
    shaped_text _shaped_text;
    aarectangle _left_to_right_caret = {};
 
    float _drag_scroll_speed_x = 0.0f;
 
    int _drag_click_count = 0;
 
    point2 _drag_select_position = {};
 
    float _text_scroll_x = 0.0f;
 
    translate2 _text_translate;
    translate2 _text_inv_translate;
 
    static constexpr hires_utc_clock::duration _blink_interval = 500ms;
    hires_utc_clock::time_point _next_redraw_time_point;
    hires_utc_clock::time_point _last_update_time_point;
 
    void revert(bool force) noexcept
    {
        if (auto delegate = _delegate.lock()) {
            _field = delegate->to_string(*this, *value);
            _error = {};
        } else {
            _field = std::string{};
            _error = l10n("missing delegate");
        }
    }
 
    void commit(bool force) noexcept
    {
        tt_axiom(gui_system_mutex.recurse_lock_count());
        if (_continues || force) {
            if (auto delegate = _delegate.lock()) {
                auto optional_value = delegate->from_string(*this, static_cast<std::string>(_field), _error);
                if (optional_value) {
                    value = *optional_value;
                }
            }
        }
    }
 
    void drag_select() noexcept
    {
        tt_axiom(gui_system_mutex.recurse_lock_count());
 
        ttlet mouseInTextPosition = _text_inv_translate * _drag_select_position;
        switch (_drag_click_count) {
        case 1: _field.dragmouse_cursorAtCoordinate(mouseInTextPosition); break;
        case 2: _field.dragWordAtCoordinate(mouseInTextPosition); break;
        case 3: _field.dragParagraphAtCoordinate(mouseInTextPosition); break;
        default:;
        }
    }
 
    void scroll_text() noexcept
    {
        if (_drag_scroll_speed_x != 0.0f) {
            _text_scroll_x += _drag_scroll_speed_x * (1.0f / 60.0f);
            drag_select();
 
            // Once we are scrolling, don't stop.
            request_redraw();
 
        } else if (_drag_click_count == 0) {
            // The following is for scrolling based on keyboard input, ignore mouse drags.
 
            // Scroll the text a quarter width to the left until the cursor is within the width
            // of the text field
            if (_left_to_right_caret.left() - _text_scroll_x > _text_rectangle.width()) {
                _text_scroll_x = _left_to_right_caret.left() - _text_rectangle.width() * 0.75f;
            }
 
            // Scroll the text a quarter width to the right until the cursor is within the width
            // of the text field
            while (_left_to_right_caret.left() - _text_scroll_x < 0.0f) {
                _text_scroll_x = _left_to_right_caret.left() - _text_rectangle.width() * 0.25f;
            }
        }
 
        // cap how far we scroll.
        ttlet max_scroll_width = std::max(0.0f, _shaped_text.preferred_extent.width() - _text_rectangle.width());
        _text_scroll_x = std::clamp(_text_scroll_x, 0.0f, max_scroll_width);
 
        // Calculate how much we need to translate the text.
        _text_translate = translate2{-_text_scroll_x, 0.0f} *
            _shaped_text.translate_base_line(point2{_text_rectangle.left(), rectangle().middle()});
        _text_inv_translate = ~_text_translate;
    }
 
    void draw_background_box(draw_context context) const noexcept
    {
        ttlet corner_shapes = tt::corner_shapes{0.0f, 0.0f, theme::global->roundingRadius, theme::global->roundingRadius};
        context.draw_box(_text_field_rectangle, background_color(), corner_shapes);
 
        ttlet line_rectangle = aarectangle{get<0>(_text_field_rectangle), extent2{_text_field_rectangle.width(), 1.0f}};
        context.draw_filled_quad(translate3{0.0f, 0.0f, 0.1f} * line_rectangle, focus_color());
    }
 
    void draw_selection_rectangles(draw_context context) const noexcept
    {
        ttlet selection_rectangles = _field.selectionRectangles();
        for (ttlet selection_rectangle : selection_rectangles) {
            context.draw_filled_quad(_text_translate * translate_z(0.1f) * selection_rectangle, theme::global->textSelectColor);
        }
    }
 
    void draw_partial_grapheme_caret(draw_context context) const noexcept
    {
        ttlet partial_grapheme_caret = _field.partialgraphemeCaret();
        if (partial_grapheme_caret) {
            context.draw_filled_quad(
                _text_translate * translate_z(0.1f) * partial_grapheme_caret, theme::global->incompleteGlyphColor);
        }
    }
 
    void draw_caret(draw_context context, hires_utc_clock::time_point display_time_point) noexcept
    {
        // Display the caret and handle blinking.
        ttlet duration_since_last_update = display_time_point - _last_update_time_point;
        ttlet nr_half_blinks = static_cast<int64_t>(duration_since_last_update / _blink_interval);
 
        ttlet blink_is_on = nr_half_blinks % 2 == 0;
        _left_to_right_caret = _field.leftToRightCaret();
        if (_left_to_right_caret && blink_is_on && _focus && window.active) {
            context.draw_filled_quad(_text_translate * translate_z(0.1f) * _left_to_right_caret, theme::global->cursorColor);
        }
    }
 
    void draw_text(draw_context context) const noexcept
    {
        context.draw_text(_shaped_text, label_color(), _text_translate * translate_z(0.2f));
    }
};
 
} // namespace tt