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

/*
 * Copyright (c) 2020-2022, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2021-2022, Linus Groh <linusg@serenityos.org>
 * Copyright (c) 2022, Sam Atkins <atkinssj@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/Debug.h>
#include <LibGfx/Painter.h>
#include <LibWeb/Geometry/DOMMatrix.h>
#include <LibWeb/HTML/Canvas/CanvasPath.h>
#include <LibWeb/HTML/Canvas/CanvasState.h>

namespace Web::HTML {

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

    Gfx::Path& mutable_path() { return static_cast<IncludingClass&>(*this).path(); }

    void scale(float sx, float sy)
    {
        dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasTransform::scale({}, {})", sx, sy);
        if (!isfinite(sx) || !isfinite(sy))
            return;
        my_drawing_state().transform.scale(sx, sy);
        flush_transform();
        mutable_path().transform(Gfx::AffineTransform().scale(1.0 / sx, 1.0 / sy));
    }

    void translate(float tx, float ty)
    {
        dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasTransform::translate({}, {})", tx, ty);
        if (!isfinite(tx) || !isfinite(ty))
            return;
        my_drawing_state().transform.translate(tx, ty);
        flush_transform();
        mutable_path().transform(Gfx::AffineTransform().translate(-tx, -ty));
    }

    void rotate(float radians)
    {
        dbgln_if(CANVAS_RENDERING_CONTEXT_2D_DEBUG, "CanvasTransform::rotate({})", radians);
        if (!isfinite(radians))
            return;
        my_drawing_state().transform.rotate_radians(radians);
        flush_transform();
        mutable_path().transform(Gfx::AffineTransform().rotate_radians(-radians));
    }

    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-transform
    void transform(double a, double b, double c, double d, double e, double f)
    {
        // 1. If any of the arguments are infinite or NaN, then return.
        if (!isfinite(a) || !isfinite(b) || !isfinite(c) || !isfinite(d) || !isfinite(e) || !isfinite(f))
            return;

        // 2. Replace the current transformation matrix with the result of multiplying the current transformation matrix with the matrix described by:
        //    a c e
        //    b d f
        //    0 0 1
        auto transform = Gfx::AffineTransform(a, b, c, d, e, f);
        my_drawing_state().transform.multiply(transform);

        if (auto inverse = transform.inverse(); inverse.has_value()) {
            mutable_path().transform(inverse.value());
        }
        flush_transform();
    }

    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-gettransform
    WebIDL::ExceptionOr<JS::NonnullGCPtr<Geometry::DOMMatrix>> get_transform()
    {
        auto& realm = static_cast<IncludingClass&>(*this).realm();
        auto transform = my_drawing_state().transform;
        Geometry::DOMMatrix2DInit init = { transform.a(), transform.b(), transform.c(), transform.d(), transform.e(), transform.f(), {}, {}, {}, {}, {}, {} };
        return Geometry::DOMMatrix::create_from_dom_matrix_2d_init(realm, init);
    }

    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-settransform
    void set_transform(double a, double b, double c, double d, double e, double f)
    {
        // 1. If any of the arguments are infinite or NaN, then return.
        if (!isfinite(a) || !isfinite(b) || !isfinite(c) || !isfinite(d) || !isfinite(e) || !isfinite(f))
            return;

        // 2. Reset the current transformation matrix to the identity matrix.
        my_drawing_state().transform = {};
        flush_transform();

        // 3. Invoke the transform(a, b, c, d, e, f) method with the same arguments.
        transform(a, b, c, d, e, f);
    }

    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-settransform-matrix
    WebIDL::ExceptionOr<void> set_transform(Geometry::DOMMatrix2DInit& init)
    {
        // 1. Let matrix be the result of creating a DOMMatrix from the 2D dictionary transform.
        auto& realm = static_cast<IncludingClass&>(*this).realm();
        auto matrix = TRY(Geometry::DOMMatrix::create_from_dom_matrix_2d_init(realm, init));

        // 2. If one or more of matrix's m11 element, m12 element, m21 element, m22 element, m41 element, or m42 element are infinite or NaN, then return.
        if (!isfinite(matrix->m11()) || !isfinite(matrix->m12()) || !isfinite(matrix->m21()) || !isfinite(matrix->m22()) || !isfinite(matrix->m41()) || !isfinite(matrix->m42()))
            return {};

        auto original_transform = my_drawing_state().transform;

        // 3. Reset the current transformation matrix to matrix.
        auto transform = Gfx::AffineTransform { static_cast<float>(matrix->a()), static_cast<float>(matrix->b()), static_cast<float>(matrix->c()), static_cast<float>(matrix->d()), static_cast<float>(matrix->e()), static_cast<float>(matrix->f()) };
        my_drawing_state().transform = transform;

        mutable_path().transform(original_transform);

        flush_transform();
        return {};
    }

    // https://html.spec.whatwg.org/multipage/canvas.html#dom-context-2d-resettransform
    void reset_transform()
    {
        // The resetTransform() method, when invoked, must reset the current transformation matrix to the identity matrix.
        my_drawing_state().transform = {};
        flush_transform();
    }

    void flush_transform()
    {
        if (auto* painter = static_cast<IncludingClass&>(*this).painter())
            painter->set_transform(my_drawing_state().transform);
    }

protected:
    CanvasTransform() = 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(); }
};

}