lighttroupe/luz

$max_previous_frame_requested ||= 0

module DrawingFrameSaving
    def frame_saving_requested?
        $max_previous_frame_requested > 0
    end

    def with_frame_saving
        #
        raise "with_frame_saving must not be called unless frame_saving_requested? returns true" unless frame_saving_requested?

        #puts "$previous_frames is not big enough" if $previous_frames.size < ($max_previous_frame_requested + 1)
        $previous_frames << get_offscreen_buffer while $previous_frames.size < ($max_previous_frame_requested + 1)
        #puts "now it has #{$previous_frames.size} frames"

        $previous_frames_current_frame_index = ($previous_frames_current_frame_index + 1) % $previous_frames.size
        #puts "saving to #{$previous_frames_current_frame_index}"

        target_buffer = $previous_frames[$previous_frames_current_frame_index]
        yield target_buffer
    end

    def with_texture_of_previous_frame(number_back)
        if $previous_frames and $previous_frames.size >= number_back
            index = $previous_frames_current_frame_index - number_back
            index += $previous_frames.size if index < 0
            #puts "chosen index=#{index} which has fbo_id=#{$previous_frames[index]}"

            $previous_frames[index].with_image {
                yield
            }
        else
            $previous_frames ||= []
            $previous_frames_current_frame_index ||= 0

            # we DON'T YIELD which ends rendering for this object-- until the frame can be generated
            #puts "(with_texture_of_previous_frame is not yielding $max_previous_frame_requested=#{$max_previous_frame_requested})"
            $max_previous_frame_requested = number_back if number_back > $max_previous_frame_requested
        end
    end
end