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* desktop: prevent duplicate launches Acquires a file lock and listens on a loopback ServerSocket in dataDir. A second launch signals the running instance to restore its window and exits silently. See plans/2026-05-13-desktop-single-instance.md. * desktop: un-minimize window in showWindow toFront() does not un-minimize a JFrame on any AWT platform. Clear the ICONIFIED bit so a minimized window restores; preserves MAXIMIZED_BOTH. Also fixes the same case when restoring from the tray icon. * desktop: move showWindow from DesktopTray to DesktopApp It has callers outside the tray (single-instance signal) and belongs next to simplexWindowState, which it operates on. * simplify * refactor * desktop: start show-file watcher when choosing minimize from first-close dialog The handleCloseRequest path already starts the watcher when minimizing to tray; the Ask-dialog path did not, so the first-time user who picks "Minimize to tray" got a hidden window with no signal handling — a duplicate launch would not restore it. * desktop: always watch for duplicate-launch signal, drop hung-instance alert The watcher now runs for the JVM lifetime once the lock is acquired, not only when minimized to tray. Duplicate launches always restore the primary's window (un-minimize, un-tray-hide, toFront) instead of being silently dropped when the primary is not minimized. Drops the "may be hung, start anyway?" popup and the two strings — that fallback was needed only because the watcher could miss signals. With the always-on watcher there is no scenario where the primary fails to consume simplex.show, so the escape hatch becomes dead code. * desktop: alert when primary's watcher doesn't consume the show file Restores the "another instance may be running" alert. Every duplicate launch waits up to 1s for the primary's watcher to delete the show file it just created. If the file is consumed within the window, the duplicate exits silently. If still there after 1s the primary is hung and the alert fires. --------- Co-authored-by: Evgeny @ SimpleX Chat <259188159+evgeny-simplex@users.noreply.github.com>
31 lines
1.8 KiB
Markdown
31 lines
1.8 KiB
Markdown
# Desktop single instance - restore on duplicate launch
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## Problem
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After tray support (#6970), the desktop app can minimize to tray. The process stays alive holding the database. When the user clicks the app launcher again (forgetting about the tray), a second process starts and either crashes on the SQLite lock or runs in a degraded state.
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## Design
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Two files in `dataDir`: `simplex.started` (lock file) and `simplex.show` (signal file).
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### Startup
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1. Try `FileChannel.tryLock(0, 1, false)` on `simplex.started`.
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2. **Lock acquired**: delete stale `simplex.show` if present (leftover from crash), start a daemon `WatchService` on `dataDir` for `ENTRY_CREATE`, start the app normally.
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3. **Lock taken** (another process holds it): create `simplex.show`, exit. The running instance detects it and shows its window.
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4. **Lock fails** (IOException, filesystem doesn't support locks, etc.): start normally but disable minimize-to-tray. Close quits the app. No worse than before tray support existed.
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### Signal handling
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While the lock is held, the daemon watcher runs for the JVM lifetime. When `simplex.show` appears it deletes the file and posts `showWindow()` to the EDT. `showWindow()` sets `windowVisible = true`, clears `ICONIFIED`, and brings the window to front — restores from tray, from taskbar-minimize, or just raises if visible-but-behind.
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Minimize-to-tray is only available when `singleInstanceLock` is held. If the lock couldn't be acquired (case 4), close always quits - preventing the scenario where two tray'd instances fight over the database.
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### Crash recovery
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The OS releases the file lock when the process dies. `simplex.show` may be left behind but is harmless - the next startup (step 2) deletes it.
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## Scope
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Linux, Windows, macOS. Per-data-directory - separate installs with different `dataDir` run independently.
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