ladybird/Libraries/LibWeb/HTML/Canvas/CanvasTextDrawingStyles.h

/*
 * Copyright (c) 2023, Bastiaan van der Plaat <bastiaan.v.d.plaat@gmail.com>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <LibWeb/CSS/Parser/Parser.h>
#include <LibWeb/CSS/StyleComputer.h>
#include <LibWeb/CSS/StyleValues/ShorthandStyleValue.h>
#include <LibWeb/DOM/Document.h>
#include <LibWeb/HTML/Canvas/CanvasState.h>

namespace Web::HTML {

// https://html.spec.whatwg.org/multipage/canvas.html#canvastextdrawingstyles
template<typename IncludingClass>
class CanvasTextDrawingStyles {
public:
    ~CanvasTextDrawingStyles() = default;

    ByteString font() const
    {
        // When font style value is empty return default string
        if (!my_drawing_state().font_style_value) {
            return "10px sans-serif";
        }

        // On getting, the font attribute must return the serialized form of the current font of the context (with no 'line-height' component).
        auto const& font_style_value = my_drawing_state().font_style_value->as_shorthand();
        auto font_style = font_style_value.longhand(CSS::PropertyID::FontStyle);
        auto font_weight = font_style_value.longhand(CSS::PropertyID::FontWeight);
        auto font_size = font_style_value.longhand(CSS::PropertyID::FontSize);
        auto font_family = font_style_value.longhand(CSS::PropertyID::FontFamily);
        return ByteString::formatted("{} {} {} {}",
            font_style->to_string(CSS::CSSStyleValue::SerializationMode::Normal),
            font_weight->to_string(CSS::CSSStyleValue::SerializationMode::Normal),
            font_size->to_string(CSS::CSSStyleValue::SerializationMode::Normal),
            font_family->to_string(CSS::CSSStyleValue::SerializationMode::Normal));
    }

    void set_font(StringView font)
    {
        // The font IDL attribute, on setting, must be parsed as a CSS <'font'> value (but without supporting property-independent style sheet syntax like 'inherit'),
        // and the resulting font must be assigned to the context, with the 'line-height' component forced to 'normal', with the 'font-size' component converted to CSS pixels,
        // and with system fonts being computed to explicit values.
        // FIXME: with the 'line-height' component forced to 'normal'
        // FIXME: with the 'font-size' component converted to CSS pixels
        auto font_style_value_result = parse_css_value(CSS::Parser::ParsingContext {}, font, CSS::PropertyID::Font);

        // If the new value is syntactically incorrect (including using property-independent style sheet syntax like 'inherit' or 'initial'), then it must be ignored, without assigning a new font value.
        // NOTE: ShorthandStyleValue should be the only valid option here. We implicitly VERIFY this below.
        if (!font_style_value_result || !font_style_value_result->is_shorthand()) {
            return;
        }
        my_drawing_state().font_style_value = font_style_value_result.release_nonnull();

        // Load font with font style value properties
        auto const& font_style_value = my_drawing_state().font_style_value->as_shorthand();
        auto& canvas_element = reinterpret_cast<IncludingClass&>(*this).canvas_element();
        auto& font_style = *font_style_value.longhand(CSS::PropertyID::FontStyle);
        auto& font_weight = *font_style_value.longhand(CSS::PropertyID::FontWeight);
        auto& font_width = *font_style_value.longhand(CSS::PropertyID::FontWidth);
        auto& font_size = *font_style_value.longhand(CSS::PropertyID::FontSize);
        auto& font_family = *font_style_value.longhand(CSS::PropertyID::FontFamily);
        auto font_list = canvas_element.document().style_computer().compute_font_for_style_values(&canvas_element, {}, font_family, font_size, font_style, font_weight, font_width);
        my_drawing_state().current_font = font_list->first();
    }

    Bindings::CanvasTextAlign text_align() const { return my_drawing_state().text_align; }
    void set_text_align(Bindings::CanvasTextAlign text_align) { my_drawing_state().text_align = text_align; }

    Bindings::CanvasTextBaseline text_baseline() const { return my_drawing_state().text_baseline; }
    void set_text_baseline(Bindings::CanvasTextBaseline text_baseline) { my_drawing_state().text_baseline = text_baseline; }

protected:
    CanvasTextDrawingStyles() = default;

private:
    CanvasState::DrawingState& my_drawing_state() { return reinterpret_cast<IncludingClass&>(*this).drawing_state(); }
    CanvasState::DrawingState const& my_drawing_state() const { return reinterpret_cast<IncludingClass const&>(*this).drawing_state(); }
};

}