lighttroupe/luz

module DrawingClipping
    def with_clip_plane(plane)
        $clip_plane_count ||= GL.GetIntegerv(GL::MAX_CLIP_PLANES)
        $next_clip_plane_index ||= 0

        return yield if $next_clip_plane_index == $clip_plane_count

        GL.Enable(GL::CLIP_PLANE0 + $next_clip_plane_index)
        GL.ClipPlane(GL::CLIP_PLANE0 + $next_clip_plane_index, plane)
        $next_clip_plane_index += 1
        yield
        $next_clip_plane_index -= 1
        GL.Disable(GL::CLIP_PLANE0 + $next_clip_plane_index)
    end

    def with_clip_plane_left_of_angle(fuzzy_angle, &proc)
        radians = RADIANS_UP + (fuzzy_angle * RADIANS_PER_CIRCLE)
        with_clip_plane([-Math.sin(radians), -Math.cos(radians), 0.0, 0.0], &proc)
    end

    def with_clip_plane_right_of_angle(fuzzy_angle, &proc)
        radians = RADIANS_UP + (fuzzy_angle * RADIANS_PER_CIRCLE)
        with_clip_plane([Math.sin(radians), Math.cos(radians), 0.0, 0.0], &proc)
    end

    def with_vertical_clip_plane_left_of(x, &proc)
        with_clip_plane([1.0, 0.0, 0.0, -x], &proc)
    end

    def with_vertical_clip_plane_right_of(x, &proc)
        with_clip_plane([-1.0, 0.0, 0.0, x], &proc)
    end

    def with_horizontal_clip_plane_above(y, &proc)
        with_clip_plane([0.0, -1.0, 0.0, y], &proc)
    end

    def with_horizontal_clip_plane_below(y, &proc)
        with_clip_plane([0.0, 1.0, 0.0, -y], &proc)
    end

    def with_clip_box(radius = 0.5, angle = 0.0)
        with_roll(angle) {
            with_vertical_clip_plane_left_of(-radius) {
                with_vertical_clip_plane_right_of(radius) {
                    with_horizontal_clip_plane_below(-radius) {
                        with_horizontal_clip_plane_above(radius) {
                            with_roll(-angle) {
                                yield
                            }
                        }
                    }
                }
            }
        }
    end
end