readTexture

		void readTexture(TextureHandle _handle, void* _data, uint8_t _mip) override
		{
			const TextureMtl& texture = m_textures[_handle.idx];

#if BX_PLATFORM_OSX
			BlitCommandEncoder bce = s_renderMtl->getBlitCommandEncoder();
			bce.synchronizeTexture(texture.m_ptr, 0, _mip);
			endEncoding();
#endif  // BX_PLATFORM_OSX

			m_cmd.kick(false, true);
			m_commandBuffer = m_cmd.alloc();


			BX_CHECK(_mip<texture.m_numMips,"Invalid mip: %d num mips:",_mip,texture.m_numMips);

			uint32_t srcWidth  = bx::uint32_max(1, texture.m_ptr.width()  >> _mip);
			uint32_t srcHeight = bx::uint32_max(1, texture.m_ptr.height() >> _mip);
			const uint8_t bpp  = bimg::getBitsPerPixel(bimg::TextureFormat::Enum(texture.m_textureFormat) );

			MTLRegion region =
			{
				{        0,         0, 0 },
				{ srcWidth, srcHeight, 1 },
			};

			texture.m_ptr.getBytes(_data, srcWidth*bpp/8, 0, region, _mip, 0);
		}