Issue 345: a calendar reminder shows transparent and empty, and the mesh had no tool to look at it

Records the symptom, what four reminders raised from a throw-away profile showed (drawn every time, at
depth 32), what that rules out, the candidates left, and what to measure at the next real reminder.
Status diagnosing: the cause is not known.

04-ISSUES/345-a-reminder-window-shows-transparent-and-empty/00-report.md

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+---
+status: diagnosing
+opened: 2026-10-09
+located-in: []
+fixed-by:
+amended-design:
+---
+
+# 345. A calendar reminder shows as a transparent, empty window, and the mesh had no tool to look at it
+
+## Symptom
+
+On 2026-10-09 the operator reported that on the workstation, when an Outlook (Exchange) meeting is
+due, the mail client's reminder window appears, but it is transparent and shows no content: no title,
+no time, no Dismiss or Snooze. The mail client is Betterbird (a Thunderbird fork, installed from the
+AUR), with the Exchange calendar through the Owl add-on. The workstation runs i3 and the `picom`
+compositor (glx backend, vsync, fading). No module owned Betterbird.
+
+The operator's view of done: *on the workstation, when an Outlook meeting is due, the reminder window
+shows the meeting (title, time, Dismiss/Snooze) on a normal background, not a transparent empty window,
+and the mesh has tools to see and fix Betterbird.*
+
+## Why it is an issue
+
+Two gaps, and the symptom itself.
+
+1. **A desktop application the operator uses every day ran outside the mesh.** Nothing could say which
+   window the reminder is, what the compositor makes of it, or which preferences the mail client runs
+   with. A change to it could only be made by hand in its profile, which the mesh's rules forbid and
+   which nothing would keep.
+2. **The tools that look at a screen could not look at this window.** The window manager's list
+   (`node-display-session.windows`) leaves out every window it does not tile, the reminder among them,
+   and says nothing a compositor decides by (a window's depth, type, opacity). The screenshot tool of the
+   display server failed for one window with `X Error BadColor (invalid Colormap parameter)
+   X_QueryColors`, because it dumped the window by its id.
+3. **The symptom's cause is not known yet.** A reminder that shows nothing is a missed meeting.
+
+The diagnosis is in [01-diagnosis.md](01-diagnosis.md).
+
+## Impact
+
+- The operator cannot read or dismiss a meeting reminder: the window is there but empty.
+- Until now, the next session that looked at it had to work around the mesh to see a window.
+
+## What is done
+
+- The display server's module gains a window list that includes unmanaged windows with their depth,
+  type, state, role and own opacity, and its screenshot of one window is cut from the screen as the
+  compositor shows it (catalogue pull request, linked from this record's pull request).
+- A `betterbird` module: status, named preferences without credentials or accounts, a user.js declared
+  through the module's setting, its log, restart, check, and a reminder on demand from a throw-away
+  profile, so a fix can be proved without touching the operator's calendar.
+
+What is not done: the cause, and so the fix. See the diagnosis.

04-ISSUES/345-a-reminder-window-shows-transparent-and-empty/01-diagnosis.md

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+# 345 — Diagnosis
+
+All times 2026-10-09, local time of the workstation. "Measured" is what a tool answered; "guess" is
+labelled as one.
+
+## The record first
+
+`records_search` for the symptom's words, `betterbird`, `thunderbird`, `picom transparent` and
+`BadColor X_QueryColors xwd`: no hits. Nothing in the record covered this.
+
+## What was measured
+
+**The client.** `betterbird-bin` 153.1.0esr-1 (application 153.1.0, build 20260820183427), foreign to the
+official repositories (from the AUR), on the workstation and on the laptop. On the workstation the main
+process had run since 2026-10-04 16:05, in the login session's scope: started by hand from the launcher,
+with no autostart entry and no line in i3's configuration. Its standard output is the login session's
+pipe that nobody reads (the same pipe as the compositor's); its standard error is `/dev/null`. So nothing
+it printed in five days was kept.
+
+**The profile in use.** Betterbird holds the installation's default profile open (99 open files), named
+by `[Install…] Default` in `profiles.ini`. Another profile is marked `Default=1`; it is not the one in
+use. The profile has no `user.js`.
+
+**Preferences that bear on how a window looks** (prefs.js, names and values only):
+`browser.display.use_system_colors` true; `extensions.activeThemeID` the built-in compact dark theme;
+`browser.theme.content-theme` and `toolbar-theme` 0; `mail.dark-reader.enabled` false. No `gfx.*`,
+`layers.*`, `widget.*` or `alerts.*` preference is set, so the renderer and the notification path are
+Betterbird's defaults. The one add-on the operator installed is Owl (Exchange). The reminder dialog's
+saved place (`xulstore.json`) is 600×300 on the right-hand monitor.
+
+**The renderer.** Both the long-running process and a fresh one load the GL libraries and run
+WebRender's threads (`Renderer`, `WRRenderBackend`, `Compositor`): hardware WebRender, in-process.
+The workstation did not suspend since boot, and the journal holds no GPU reset.
+
+**The reminder window.** A reminder was raised without the operator's calendar: a second Betterbird with
+`--no-remote` in a throw-away profile under the account's runtime directory, holding one local calendar
+file with one event whose reminder was due 30 to 40 seconds after the start. Four runs:
+
+| run | profile | window | depth | drawn |
+|---|---|---|---|---|
+| 1, 11:43 | Betterbird's defaults | class `Calendar` / `eu.betterbird.Betterbird`, role `AlarmWindow`, type `DIALOG`, 600×300, floating | 32 | not captured: it was snoozed from the desk at 11:44, before the image was taken (the calendar file recorded the snooze) |
+| 2, 11:49 | the same; the snoozed reminder again | the same | 32 | **yes**: title, time, Snooze for, Dismiss, on a dark background |
+| 3, 11:52 | with the operator's theme, `use_system_colors`, fonts and the dialog's saved place | the same | 32 | **yes** |
+| 4, 11:54 | as 3, with `mozilla.widget.use-argb-visuals` false | the same | **still 32** | yes |
+
+Each image was taken from the whole screen at the window's place and looked at. Every Betterbird window
+on the workstation has depth 32 (an ARGB visual), the long-running one's mail window included.
+
+**The screenshot tool's failure.** `xorg_screenshot` of the whole screen worked; of one window it
+dumped the window by its id (`xwd -id`): that is the call reported failing with BadColor, and here it
+answered BadWindow for a window that had just closed.
+
+## What follows from it (guesses, each said as one)
+
+- **Why "transparent" rather than black.** A window of depth 32 that its program never drew holds
+  zero alpha, and picom blends it with what is behind it: it looks transparent, with i3's frame around
+  it. That matches the report exactly. So the window is very likely **mapped but not painted** by
+  Betterbird. That is a guess from how compositing works; it was not seen, because the symptom did not
+  happen in four runs.
+- **Not the preferences found.** The operator's theme and colour switch drew the reminder correctly in
+  a fresh process (run 3). The preference that would take away the alpha visual does not change the
+  depth in this version (run 4), so it is no lever.
+- **Candidates not yet ruled out:**
+  1. the long-running process: five days of uptime, with WebRender's per-window state recreated many
+     times (its thread names count to 15). A fresh process drew every reminder;
+  2. Owl's reminders, which the test cannot raise without the operator's account;
+  3. the moment it appears: a reminder raised while a full-screen window holds the focused workspace
+     (Slack and a game were full screen on the day), or on the right-hand monitor where it was saved.
+
+## What would decide it
+
+At the next real reminder, before touching it:
+
+1. `xorg_windows` with class `Calendar` on the workstation: the window's map state and depth.
+2. `xorg_screenshot` with that window and `inline`: what the screen shows.
+3. `betterbird_status`: how long the process has run.
+
+If the window is mapped and empty, `betterbird_restart` (which also sends its output to the journal,
+so the next failure leaves a trace) and `betterbird_reminder_test` with `carry` of the theme show
+whether a fresh process draws it. If it does, candidate 1 holds, and the fix is in Betterbird or in its
+renderer, not in the mesh; a preference to try then (`gfx.webrender.software` true, declared through the
+module's setting) is proved with the same test before the operator relies on it.
+
+Until then this record stays `diagnosing`, and the acceptance sentence is not met.