linebender/druid · error

Destroying a buffer while it is in use

Error message

Destroying a buffer while it is in use

What it means

Guard panic in Buffer::destroy: the buffer is still marked in-use (attached to a surface and not yet released by the compositor), so destroying it now would violate the wl_buffer protocol and cause protocol errors. It fires when caller code tears down a surface's buffer pool before the compositor has released the buffer.

Solutions

1. Wait for the compositor's wl_buffer.release event and clear the in_use flag before calling destroy
2. Defer destruction of the buffer to the release callback or drop path
3. If the surface is being torn down, let the compositor clean up by dropping the wl_buffer proxy without an explicit destroy-while-attached

When it happens

Trigger: Thrown at druid-shell/src/backend/wayland/surfaces/buffers.rs:293 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of linebender/druid@0f8b1195e4 (2026-09-10). Data as JSON: /api/errors/f9b4944e4e320ecf. Report an issue: GitHub.

Appendix: source

Thrown at druid-shell/src/backend/wayland/surfaces/buffers.rs:293

                }
                _ => tracing::warn!("unhandled wayland buffer event: {:?} {:?}", b, event),
            }
        }));

        Buffer { inner, in_use }
    }

    pub fn attach(&self, wl_surface: &wl::Main<WlSurface>) {
        if self.in_use.get() {
            panic!("attaching an already in-use surface");
        }
        self.in_use.set(true);
        wl_surface.attach(Some(&self.inner), 0, 0);
    }

    pub fn destroy(&self) {
        if self.in_use.get() {
            panic!("Destroying a buffer while it is in use");
        }
        self.inner.destroy();
    }
}

pub struct BufferData<const N: usize> {
    buffers: WeakRc<Buffers<N>>,
    mmap: Mmap,
}

impl<const N: usize> Deref for BufferData<N> {
    type Target = [u8];

    fn deref(&self) -> &[u8] {
        self.mmap.deref()
    }
}

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