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drm/compositor: fall back to primary-plane cursor on map_mut failure #2033

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drm/compositor: fall back to primary-plane cursor on map_mut failure #2033

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88 changes: 49 additions & 39 deletions src/backend/drm/compositor/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3312,45 +3312,55 @@ where
}
}?;

let ret = cursor_buffer
.map_mut::<_, Result<_, PixmanError>>(
0,
0,
cursor_buffer_size.w as u32,
cursor_buffer_size.h as u32,
|mbo| {
let plane_pixman_format = pixman::FormatCode::try_from(DrmFourcc::Argb8888).unwrap();
let mut cursor_dst = unsafe {
pixman::Image::from_raw_mut(
plane_pixman_format,
mbo.width() as usize,
mbo.height() as usize,
mbo.buffer_mut().as_mut_ptr() as *mut u32,
mbo.stride() as usize,
false,
)
}
.map_err(|_| PixmanError::ImportFailed)?;
let mut framebuffer = pixman_renderer.bind(&mut cursor_dst)?;
let mut frame =
pixman_renderer.render(&mut framebuffer, cursor_plane_size, output_transform)?;
frame.clear(Color32F::TRANSPARENT, &[Rectangle::from_size(cursor_plane_size)])?;
let src = element.src();
let dst = Rectangle::from_size(element_geometry.size);
frame.render_texture_from_to(
&cursor_texture,
src,
dst,
&[dst],
&[],
element.transform(),
element.alpha(),
)?;
let _ = frame.finish()?.wait(); // what can we do?
Ok(())
},
)
.expect("Lost track of cursor device");
let map_result = cursor_buffer.map_mut::<_, Result<_, PixmanError>>(
0,
0,
cursor_buffer_size.w as u32,
cursor_buffer_size.h as u32,
|mbo| {
let plane_pixman_format = pixman::FormatCode::try_from(DrmFourcc::Argb8888).unwrap();
let mut cursor_dst = unsafe {
pixman::Image::from_raw_mut(
plane_pixman_format,
mbo.width() as usize,
mbo.height() as usize,
mbo.buffer_mut().as_mut_ptr() as *mut u32,
mbo.stride() as usize,
false,
)
}
.map_err(|_| PixmanError::ImportFailed)?;
let mut framebuffer = pixman_renderer.bind(&mut cursor_dst)?;
let mut frame =
pixman_renderer.render(&mut framebuffer, cursor_plane_size, output_transform)?;
frame.clear(Color32F::TRANSPARENT, &[Rectangle::from_size(cursor_plane_size)])?;
let src = element.src();
let dst = Rectangle::from_size(element_geometry.size);
frame.render_texture_from_to(
&cursor_texture,
src,
dst,
&[dst],
&[],
element.transform(),
element.alpha(),
)?;
let _ = frame.finish()?.wait(); // what can we do?
Ok(())
},
);
// The map itself can fail (e.g. the device went away, or — on NVIDIA — a
// transient ENOMEM from the kernel allocator after a GPU-memory leak in
// another client). Skip the cursor plane on any such failure so the cursor
// falls back to being composited on the primary plane, matching how every
// other failure point above this one recovers.
let ret = match map_result {
Ok(ret) => ret,
Err(err) => {
debug!("failed to map cursor buffer for rendering: {err}");
return None;
}
};

@Drakulix Drakulix May 22, 2026

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Could this simply be a inspect_err followed by .ok()?.

Also I appreciate the PR description and long commit message, but this comment here is really not necessary. We simply fall back in an error case. If anybody wonders how to even reach this condition, they can use git blame.


if let Err(err) = ret {
debug!("{err}");
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