lighttroupe/luz

module EngineRendering
    def render(enable_frame_saving)
        $gui.render {
            if enable_frame_saving && frame_saving_requested?
                render_with_frame_saving
            else
                render_without_frame_saving
            end
        }
    end

    def with_content_aspect_ratio
        with_scale(0.62, 1.0) {            # TODO: proper numbers
            yield
        }
    end

    def render_with_frame_saving
        with_frame_saving { |target_buffer|
            target_buffer.using(:clear => true) {
                with_content_aspect_ratio {        # TODO: properly set aspect ratio
                    render_without_frame_saving
                }
            }
            # draw created image to screen
            target_buffer.with_image {
                fullscreen_rectangle
            }
        }
    end

    def render_without_frame_saving
        render_recursively(@project.effects) { }
    end

    #
    # NOTE: This is a prototype for a generic recursive renderer, to replace that of actors/directors and maybe themes/variables/events
    #
    def render_recursively(user_objects, index=0, &proc)
        uo = user_objects[index]
        return proc.call unless uo

        if uo.usable?
            $engine.user_object_try(uo) {
                uo.resolve_settings
                uo.tick!
                uo.render {
                    render_recursively(user_objects, index+1, &proc)        # continue (potentially multiple times-- this is how Grid and other child-creating plugins work)
                }
            }
        else
            render_recursively(user_objects, index+1, &proc)                # skip
        end
    end

    #
    # OpenGL
    #
    def set_opengl_projection
        @camera_distance_from_origin = 0.5

        # TODO: comment formula below
        angle = 2.0 * Math.atan(0.5 / @camera_distance_from_origin) * RADIANS_TO_DEGREES

        GL.MatrixMode(GL::PROJECTION)
        GL.LoadIdentity

        GLU.Perspective(angle, 1.0, 0.001, 1024.0)        # 1.0 is output ratio. NOTE: near/far clip plane numbers are somewhat arbitrary.
    end

    def set_opengl_view
        GL.MatrixMode(GL::MODELVIEW)
        GL.LoadIdentity
        GL.Translate(0,0,-@camera_distance_from_origin) # NOTE: makes a 1x1 object at the origin visible/fullscreen
    end

    def set_opengl_defaults
        GL.Enable(GL::BLEND)
        GL.BlendFunc(GL::SRC_ALPHA, GL::ONE_MINUS_SRC_ALPHA)

        # POLYGON_SMOOTH causes seams on NVidia hardware
        #GL.Enable(GL::POLYGON_SMOOTH)
        #GL.Hint(GL::POLYGON_SMOOTH_HINT, GL::NICEST)

        GL.ShadeModel(GL::FLAT)            # TODO: probably want to change this

        # When using painter's algorithm for 2D, no need for depth test
        GL.Disable(GL::DEPTH_TEST)

        # Many effects rely on the backface to be visible (eg. flip_horizontally)
        GL.Disable(GL::CULL_FACE)
        GL.PolygonMode(GL::FRONT, GL::FILL)
        GL.PolygonMode(GL::BACK, GL::FILL)

        GL.Enable(GL::TEXTURE_2D)
    end
end