scythe/src/capture/windows.rs

#[cfg(target_os = "windows")]
use windows::{
    core::Interface,
    Win32::Foundation::*,
    Win32::Graphics::Direct3D::*,
    Win32::Graphics::Direct3D11::*,
    Win32::Graphics::Dxgi::Common::*,
    Win32::Graphics::Dxgi::*,
    Win32::System::Com::*,
};
use crate::capture::{Frame, FrameSource};

#[cfg(target_os = "windows")]
pub struct WindowsCapture {
    device: ID3D11Device,
    context: ID3D11DeviceContext,
    duplication: IDXGIOutputDuplication,
    gpu_texture: ID3D11Texture2D,
    width: u32,
    height: u32,
}

#[cfg(target_os = "windows")]
unsafe impl Send for WindowsCapture {}

#[cfg(target_os = "windows")]
impl WindowsCapture {
    pub fn new() -> Result<Self, Box<dyn std::error::Error + Send + Sync>> {
        unsafe {
            // Initialize COM library on capture thread
            let _ = CoInitializeEx(None, COINIT_MULTITHREADED);

            // Create D3D11 hardware device
            let mut device: Option<ID3D11Device> = None;
            let mut context: Option<ID3D11DeviceContext> = None;
            let mut feature_level = D3D_FEATURE_LEVEL_11_0;

            D3D11CreateDevice(
                None,
                D3D_DRIVER_TYPE_HARDWARE,
                None,
                D3D11_CREATE_DEVICE_BGRA_SUPPORT,
                Some(&[D3D_FEATURE_LEVEL_11_1, D3D_FEATURE_LEVEL_11_0]),
                D3D11_SDK_VERSION,
                Some(&mut device),
                Some(&mut feature_level),
                Some(&mut context),
            )?;

            let device = device.ok_or("Failed to create D3D11 device")?;
            let context = context.ok_or("Failed to create D3D11 context")?;

            // Retrieve DXGI Output for the primary display
            let dxgi_device: IDXGIDevice = device.cast()?;
            let adapter = dxgi_device.GetAdapter()?;
            let output = adapter.EnumOutputs(0)?;
            let output1: IDXGIOutput1 = output.cast()?;

            let desc = output.GetDesc()?;
            let width = (desc.DesktopCoordinates.right - desc.DesktopCoordinates.left) as u32;
            let height = (desc.DesktopCoordinates.bottom - desc.DesktopCoordinates.top) as u32;

            // Initialize Desktop Duplication
            let duplication = output1.DuplicateOutput(&device)?;

            // Allocate a dedicated VRAM-resident GPU texture for 100% zero-copy capture
            // (Frame stays on GPU die, zero PCIe bus readback, 0% CPU consumption)
            let gpu_desc = D3D11_TEXTURE2D_DESC {
                Width: width,
                Height: height,
                MipLevels: 1,
                ArraySize: 1,
                Format: DXGI_FORMAT_B8G8R8A8_UNORM,
                SampleDesc: DXGI_SAMPLE_DESC { Count: 1, Quality: 0 },
                Usage: D3D11_USAGE_DEFAULT,
                BindFlags: (D3D11_BIND_RENDER_TARGET.0 | D3D11_BIND_SHADER_RESOURCE.0) as u32,
                CPUAccessFlags: 0,
                MiscFlags: 0,
            };

            let mut gpu_texture: Option<ID3D11Texture2D> = None;
            device.CreateTexture2D(&gpu_desc, None, Some(&mut gpu_texture))?;
            let gpu_texture = gpu_texture.ok_or("Failed to create GPU VRAM texture")?;

            println!("Windows DXGI Hardware Capture active (Pure GPU Zero-Copy): {}x{}", width, height);

            Ok(Self {
                device,
                context,
                duplication,
                gpu_texture,
                width,
                height,
            })
        }
    }

    fn reinit_duplication(&mut self) -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
        unsafe {
            let dxgi_device: IDXGIDevice = self.device.cast()?;
            let adapter = dxgi_device.GetAdapter()?;
            let output = adapter.EnumOutputs(0)?;
            let output1: IDXGIOutput1 = output.cast()?;
            self.duplication = output1.DuplicateOutput(&self.device)?;
            Ok(())
        }
    }
}

#[cfg(target_os = "windows")]
impl FrameSource for WindowsCapture {
    fn next_frame(&mut self) -> Result<Frame, Box<dyn std::error::Error + Send + Sync>> {
        unsafe {
            let mut frame_info = DXGI_OUTDUPL_FRAME_INFO::default();
            let mut desktop_resource: Option<IDXGIResource> = None;

            for _ in 0..5 {
                match self.duplication.AcquireNextFrame(150, &mut frame_info, &mut desktop_resource) {
                    Ok(()) => {
                        if let Some(resource) = desktop_resource {
                            let texture: ID3D11Texture2D = resource.cast()?;
                            
                            // Copy directly on the GPU from the desktop buffer to our persistent VRAM texture
                            self.context.CopyResource(&self.gpu_texture, &texture);
                            
                            // Immediately release the desktop frame back to the DWM compositor
                            let _ = self.duplication.ReleaseFrame();

                            // Pass the VRAM texture handle directly to the hardware encoder (Zero CPU copy!)
                            return Ok(Frame::D3D11Texture {
                                handle: self.gpu_texture.as_raw() as usize,
                            });
                        }
                        let _ = self.duplication.ReleaseFrame();
                    }
                    Err(e) if e.code() == DXGI_ERROR_WAIT_TIMEOUT => {
                        // Display is idle (no new pixels), yield current texture without spinning CPU
                        std::thread::sleep(std::time::Duration::from_millis(8));
                        return Ok(Frame::D3D11Texture {
                            handle: self.gpu_texture.as_raw() as usize,
                        });
                    }
                    Err(e) if e.code() == DXGI_ERROR_ACCESS_LOST => {
                        println!("DXGI access lost (display mode or fullscreen switch), reacquiring...");
                        let _ = self.reinit_duplication();
                        std::thread::sleep(std::time::Duration::from_millis(50));
                        continue;
                    }
                    Err(e) => {
                        return Err(Box::new(e));
                    }
                }
            }

            Ok(Frame::D3D11Texture {
                handle: self.gpu_texture.as_raw() as usize,
            })
        }
    }
}