pub fn do_draw(
        &mut self,
        _window: &winit::window::Window,
        _time_state: &TimeState
    )
        -> Result<(), ash::vk::Result>
    {
        let frame_fence = self.swapchain.in_flight_fences[self.sync_frame_index];

        // Wait if two frame are already in flight
        unsafe {
            self.device.logical_device.wait_for_fences(&[frame_fence], true, std::u64::MAX).unwrap();
            self.device.logical_device.reset_fences(&[frame_fence]).unwrap();
        }

        let (present_index, _is_suboptimal) = unsafe {
            self.swapchain
                .swapchain_loader
                .acquire_next_image(
                    self.swapchain.swapchain,
                    std::u64::MAX,
                    self.swapchain.image_available_semaphores[self.sync_frame_index],
                    vk::Fence::null(),
                )?
        };

        let wait_semaphores = [self.swapchain.image_available_semaphores[self.sync_frame_index]];
        let signal_semaphores = [self.swapchain.render_finished_semaphores[self.sync_frame_index]];

        let wait_dst_stage_mask = [vk::PipelineStageFlags::COLOR_ATTACHMENT_OUTPUT];
        let command_buffers = [self.pipeline.command_buffers[present_index as usize]];

        //add fence to queue submit
        let submit_info = [
            vk::SubmitInfo::builder()
                .wait_semaphores(&wait_semaphores)
                .signal_semaphores(&signal_semaphores)
                .wait_dst_stage_mask(&wait_dst_stage_mask)
                .command_buffers(&command_buffers)
                .build()
        ];

        unsafe {
            self.device.logical_device
                .queue_submit(self.device.queues.graphics_queue, &submit_info, frame_fence)
                .expect("queue submit failed.");
        }

        let wait_semaphors = [self.swapchain.render_finished_semaphores[self.sync_frame_index]];
        let swapchains = [self.swapchain.swapchain];
        let image_indices = [present_index];
        let present_info = vk::PresentInfoKHR::builder()
            .wait_semaphores(&wait_semaphors) // &base.rendering_complete_semaphore)
            .swapchains(&swapchains)
            .image_indices(&image_indices);

        unsafe {
            self.swapchain.swapchain_loader
                .queue_present(self.device.queues.present_queue, &present_info)
                .unwrap();
        }

        self.sync_frame_index = (self.sync_frame_index + 1) % MAX_FRAMES_IN_FLIGHT;

        Ok(())
    }