linebender/druid · error

after rendering, no pixmap to present

Error message

after rendering, no pixmap to present

What it means

After rendering completes, `Window::render` pops an idle pixmap from the buffer pool to present to the X server; this error fires when the pool is empty, so there is no free pixmap to present. This indicates the double/triple-buffering invariant was violated — more frames are in flight than the pool has buffers, or presentation bookkeeping failed to return buffers to the idle list.

Solutions

1. Verify the X server supports DRI3/Present and that present events are being delivered (test with a compositor disabled/enabled).
2. Check that every present path returns its pixmap to idle_pixmaps (or pops it consistently) — a missed event leaves the pool empty.
3. Reduce redraw pressure or investigate frame pacing; rendering more frames than buffers can deadlock the pool.
4. Update druid-shell; the X11 present buffer logic has had fixes around lost idle pixmaps.

Example fix

// before
let pixmap = *buffers
    .idle_pixmaps
    .last()
    .ok_or_else(|| anyhow!("after rendering, no pixmap to present"))?;
// after
if buffers.idle_pixmaps.is_empty() {
    log::warn!("no idle pixmap to present; skipping frame");
    return Ok(());
}
let pixmap = *buffers.idle_pixmaps.last().unwrap();

// app-level: avoid issuing more redraws than frames presented
if window.needs_present() { return; } // a frame is already in flight
window.request_redraw();

fn has_idle_pixmap(buffers: &SurfaceBuffers) -> bool {
    !buffers.idle_pixmaps.is_empty()
}

match window.render() {
    Err(e) if e.to_string().contains("no pixmap to present") => {
        log::warn!("present pool exhausted; waiting for PresentComplete before next frame");
        window.request_redraw(); // retry once buffers return
    },
    other => other,
}

When it happens

Trigger: `render` (from `redraw_now`/`handle_complete_notify`) calls `set_needs_present(false)`, borrows `buffers`, and finds `idle_pixmaps` empty because all pixmaps are still in flight (present pending, no PresentComplete processed) or `present_data` was None so earlier frames never consumed/popped correctly.

Common situations: X server not sending PresentCompleteNotify events (compositor issues, broken DRI3/Present extension), rendering faster than the display refresh/present completion, or a prior present error that left buffers un-returned.

Related errors

• Failed to update cairo drawable
• Window::render - piet finish failed
• called request_paint during painting
• attaching an already in-use surface
• unexpected mouse wheel button

AI-assisted analysis of linebender/druid@0f8b1195e4 (2026-09-10). Data as JSON: /api/errors/c5c1c2c38bf8be8c. Report an issue: GitHub.

Appendix: source

Thrown at druid-shell/src/backend/x11/window.rs:827

                        .map_err(|e| anyhow!("Window::render - piet finish failed: {}", e))
                }
                Some(e) => {
                    // Finish might have errored, in which case we want to propagate it.
                    e
                }
            };
            cairo_ctx.reset_clip();

            err?;
        }

        self.set_needs_present(false)?;

        let mut buffers = borrow_mut!(self.buffers)?;
        let pixmap = *buffers
            .idle_pixmaps
            .last()
            .ok_or_else(|| anyhow!("after rendering, no pixmap to present"))?;
        let scale = self.scale.get();
        if let Some(present) = borrow_mut!(self.present_data)?.as_mut() {
            present.present(self.app.connection(), pixmap, self.id, &invalid, scale)?;
            buffers.idle_pixmaps.pop();
        } else {
            for rect in invalid.rects() {
                let rect = rect.to_px(scale).round();
                let (x, y) = (rect.x0 as i16, rect.y0 as i16);
                let (w, h) = (rect.width() as u16, rect.height() as u16);
                self.app
                    .connection()
                    .copy_area(pixmap, self.id, self.gc, x, y, x, y, w, h)?;
            }
        }
        Ok(())
    }

    fn show(&self) {

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