// QUESTION: This is in the vertex shader.. it doesn't seem to matter if binding = 0 or 2
// VERTEX SHADER: https://github.com/aclysma/test_rendy_imgui/blob/master/assets/gui.vert
/*
layout(set = 0, binding = 2) uniform Args {
    mat4 mvp;
};
*/

// Descriptor layout() impl
fn layout(&self) -> Layout {
        return Layout {
            sets: vec![SetLayout {
                bindings: vec![
                    gfx_hal::pso::DescriptorSetLayoutBinding {
                        binding: 0,
                        ty: gfx_hal::pso::DescriptorType::SampledImage,
                        count: 1,
                        stage_flags: gfx_hal::pso::ShaderStageFlags::FRAGMENT,
                        immutable_samplers: false,
                    },
                    gfx_hal::pso::DescriptorSetLayoutBinding {
                        binding: 1,
                        ty: gfx_hal::pso::DescriptorType::Sampler,
                        count: 1,
                        stage_flags: gfx_hal::pso::ShaderStageFlags::FRAGMENT,
                        immutable_samplers: false,
                    },
                    gfx_hal::pso::DescriptorSetLayoutBinding {
// QUESTION: does this binding ID matter? It will crash if it's 0, but I think it's just because there is already a binding above
                        binding: 2,
                        ty: gfx_hal::pso::DescriptorType::UniformBuffer,
                        count: 1,
                        stage_flags: gfx_hal::pso::ShaderStageFlags::VERTEX,
                        immutable_samplers: false,
                    },
                ],
            }],
            push_constants: vec![/*(gfx_hal::pso::ShaderStageFlags::VERTEX, 0..16)*/],
        };
    }
}

// Descriptor build() impl
    fn build<'a>(
        self,
        _ctx: &GraphContext<B>,
        factory: &mut Factory<B>,
        queue: QueueId,
        aux: &Resources,
        buffers: Vec<NodeBuffer>,
        images: Vec<NodeImage>,
        set_layouts: &[Handle<DescriptorSetLayout<B>>],
    ) -> Result<ImguiRenderPipeline<B>, failure::Error> {
        assert!(buffers.is_empty());
        assert!(images.is_empty());
        assert_eq!(set_layouts.len(), 1);

        // other setup first...
        unsafe {
            use gfx_hal::device::Device;
            factory.device().write_descriptor_sets(vec![
                gfx_hal::pso::DescriptorSetWrite {
                    set: descriptor_set.raw(),
                    binding: 0,
                    array_offset: 0,
                    descriptors: vec![gfx_hal::pso::Descriptor::Image(
                        texture.view().raw(),
                        gfx_hal::image::Layout::ShaderReadOnlyOptimal,
                    )],
                },
                gfx_hal::pso::DescriptorSetWrite {
                    set: descriptor_set.raw(),
                    binding: 1,
                    array_offset: 0,
                    descriptors: vec![gfx_hal::pso::Descriptor::Sampler(texture.sampler().raw())],
                },
                gfx_hal::pso::DescriptorSetWrite {
                    set: descriptor_set.raw(),
// QUESTION: Does this binding ID matter?
                    binding: 0,
                    array_offset: 0,
                    descriptors: vec![gfx_hal::pso::Descriptor::Buffer(
                        uniform_buf.raw(),
                        Some(0)..Some(UNIFORM_SIZE),
                    )],
                },
            ]);
        }