Struct GpuReadback 

pub struct GpuReadback { /* private fields */ }

Headless EGL/GLES context for reading a capture dma-buf back to CPU RGBA pixels.

The GPU capture path hands out a wl::DmabufFrame (zero-copy, meant for display). Tools that ultimately need CPU pixels — screenshot encoding today, video/timelapse on the roadmap — use this to import that dma-buf as a GL texture and glReadPixels it into RGBA8. It runs without a window: a 1×1 pbuffer keeps it portable across drivers that lack surfaceless contexts. Build one and reuse it across frames (the EGL setup is not free).

Implementations

impl GpuReadback

pub fn new() -> Result<Self>

Create the offscreen context. Errors (rather than panicking, unlike Gpu::new) since callers can fall back to the shm capture path.

pub fn readback(&mut self, frame: DmabufFrame) -> Result<CapturedImage>

Import frame’s dma-buf as a GL texture and read it back to RGBA8. Alpha is forced opaque: captures are opaque and XRGB dma-bufs leave the X byte undefined (mirrors the shm path’s handling of alpha-less formats).