Rebuild the main window and react to WebView2 ProcessFailed - #448
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Follow-up to btsouth#444 for btsouth#410. That change drops a dead flyout, Settings or FloatBar window the next time it is opened; this one covers the two gaps it left: the main window, and windows that are on screen when their browser process dies. Main window. Its open paths (tray menu, Ctrl+Shift+U, set_surface_mode) run on the main thread or in sync commands, where destroying and rebuilding a window inline would block the event loop that has to process Destroyed. shell/window_recovery.rs therefore probes main before every transition and, when it is dead, hands destroy + rebuild to a std::thread and abandons the attempt. The probe is pure Win32 on the native handle captured at build time, so it never waits on the event loop while SHELL_TRANSITION_SERIAL is held. The rebuild uses WebviewWindowBuilder::from_config over the tauri.conf.json entry, so the new window inherits "visible": false and every other declared property, resets the surface state to Hidden to match, then replays the pending request on the main thread via run_on_main_thread. Every path that can notice a dead main (the transition guards, hide-to-tray, ProcessFailed) merges its request into one pending replay, so whichever wins the race to start the rebuild, an open issued meanwhile is still honoured. The replay must not run on the rebuild thread: a transition holds SHELL_TRANSITION_SERIAL while it calls window getters, and a freshly built window receives a Focused(true)/Focused(false) pair whose handler takes the same lock on the main thread, which deadlocked the whole app on every rebuild of a visible main window. ProcessFailed. shell/webview_lifecycle.rs subscribes every window the app builds (main, flyout, Settings, FloatBar, and every rebuilt window) to CoreWebView2's ProcessFailed event through webview2-com, which wry already depends on. Every failure logs a warn with the kind and label. BrowserProcessExited leaves the control unusable and rebuilds the window; RenderProcessExited gets a new render process from WebView2 itself and only reloads the page; the helper-process kinds are log-only. The handler runs inside the COM callback on the UI thread, so it only reads is_visible and outer_position and dispatches: a window that was visible is rebuilt and shown again through its own first-build path (main replays the current surface at its old position, Settings reopens on its default tab at its remembered geometry, the flyout goes through the visible(false) then frontend-reveal handshake); a hidden window is torn down so its next open is a plain first build. main is always rebuilt, hidden, so the next tray click is instant. The FloatBar is torn down and re-applied from settings, since an enabled bar is never re-shown and would otherwise stay blank. Per-window in-flight flags keep the concurrent rebuilds a shared browser process exit causes from stacking, and clear themselves if a rebuild thread panics. webview_recovery gains destroy_and_release for the rebuild threads: Tauri releases a destroyed window's label only when the event loop processes Destroyed, after destroy() returned, and a rebuild issued before that fails with "a window with label already exists". The wait compares native handles, so an open that races the teardown and rebuilds the window first ends the wait instead of timing it out against the new window, and it is bounded in polls rather than wall-clock time because each poll can block behind another window's build on the main thread. The flyout opener waits for an in-flight teardown of its own window for the same reason. The flyout's Focused(false) handler now ignores a never-shown window. Windows reports a focus loss when a hidden window is activated without foreground rights, which happens right after build; treating it as a dismiss cleared the pending reveal and left the rebuilt flyout invisible. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_017ykxBKGpjDqrWQj7JQVRNm
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Included review availability: Your plan provides up to 1 included review per hour; 0 remain after this review. 📝 WalkthroughWalkthroughAdds Windows WebView2 ChangesWebView2 window recovery
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~45 minutes Change: Bug fix Merge Risk: ⚪ Minimal · up to No concrete merge-blocking behavior regression is established in the available context. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
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In `@apps/desktop-tauri/src-tauri/src/shell/flyout_window.rs`:
- Line 191: Update the visibility fallback in the flyout dismissal logic around
window.is_visible() to use false instead of true, so query failures are treated
as not visible and do not clear the pending reveal or hide the rebuilt flyout.
In `@apps/desktop-tauri/src-tauri/src/shell/window_recovery.rs`:
- Around line 263-264: Update the main rebuild completion flow around
main_rebuild and dispatch_main_rebuild so replay extraction, in_flight clearing,
and queued-request handoff occur atomically under the same MAIN_REBUILD lock.
Ensure requests arriving during completion are either replayed on the rebuilt
window or start a new worker rather than remaining queued, and add a
synchronized concurrency test covering this ordering.
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apps/desktop-tauri/src-tauri/Cargo.tomlapps/desktop-tauri/src-tauri/src/floatbar/window.rsapps/desktop-tauri/src-tauri/src/main.rsapps/desktop-tauri/src-tauri/src/shell/flyout_window.rsapps/desktop-tauri/src-tauri/src/shell/mod.rsapps/desktop-tauri/src-tauri/src/shell/settings_window.rsapps/desktop-tauri/src-tauri/src/shell/transition.rsapps/desktop-tauri/src-tauri/src/shell/webview_lifecycle.rsapps/desktop-tauri/src-tauri/src/shell/window.rsapps/desktop-tauri/src-tauri/src/shell/window_recovery.rsapps/desktop-tauri/src-tauri/src/webview_recovery.rs
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The rebuild worker took its replay and released the in-flight slot in two separate lock scopes. A request that landed between them was merged into the queue after the take and, with the slot still marked taken, did not spawn a rebuild of its own; the worker then released the slot without looking again, leaving the request queued until the next crash. `MainRebuild::finish` now does both steps under a single guard, mirrored by `enqueue` on the dispatch side, with a threaded test that races the two and requires every interleaving to hand the request to exactly one side. Also treat a failed `is_visible()` query on the flyout as "not visible" so a blur reaching a mid-teardown window cannot clear the pending reveal. Addresses the two CodeRabbit findings on btsouth#448. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01FsB5pGSpYBAW4pg5TWfeXJ
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PR B (the flyout open serialization + the root ErrorBoundary) is ready and stacked on this branch: diogochaves/ceiling@410-follow-up...410-pr-b It's two commits (if you want to read ahead). I'll open it against main once this one lands so the diff stays clean. |
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Read through properly, this is in good shape. The policy split with tests, the handle comparison in One thing before merge, in I am happy to push that myself if it is easier, just say. Otherwise I will merge as soon as it is in. |
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Follow-up to #444 for #410, covering the two gaps that change named: the main window, and windows that are on screen when their browser process dies.
Main window. Its open paths (tray menu,
Ctrl+Shift+U,set_surface_mode) run on the main thread or in sync commands, where destroying and rebuilding a window inline would block the event loop that has to processDestroyed. Newshell/window_recovery.rsprobesmainbefore every transition and, when it is dead, hands destroy + rebuild to astd::threadand abandons that attempt. The probe is pure Win32 on the native handle captured at build time (register_main), so it never waits on the event loop whileSHELL_TRANSITION_SERIALis held; some transitions run from spawned tasks, and a marshalled getter under that lock can wait on a main thread that is itself waiting for the lock. The rebuild usesWebviewWindowBuilder::from_configover thetauri.conf.jsonentry, so the new window inherits"visible": falseand every other declared property exactly as at startup, resets the surface state toHiddento match, and then replays the pending request on the main thread so the click that hit the dead window still does what the user asked, a beat later. Every path that can notice a deadmain(the transition guards, hide-to-tray, theProcessFailedhandler) merges its request into one pending replay, so it does not matter which of them wins the race to start the rebuild: an open issued while a rebuild is in flight is queued, not dropped. The policies (guard_action,merge_replay) are pure functions with unit tests.ProcessFailed. New
shell/webview_lifecycle.rssubscribes every window the app builds (main, flyout, Settings, FloatBar, and every rebuilt window) toCoreWebView2'sProcessFailedevent. Every failure logs a warn with the kind and the label, as requested. Per the WebView2 docs,BrowserProcessExitedleaves the control unusable and rebuilds the window;RenderProcessExitedgets a fresh render process from WebView2 itself and only reloads the page (deferred throughrun_on_main_threadso it never re-enters WebView2 from inside its own callback;?tab=survives, so Settings comes back on the same tab); the helper-process kinds are log-only. This is unit-tested. The handler runs inside the COM callback on the UI thread, so it only readsis_visibleandouter_positionand dispatches towindow_recovery: a window that was visible is rebuilt and shown again through its own first-build path, a hidden one is torn down so its next open is a plain first build.mainis always rebuilt, hidden, so the next tray click is instant. The FloatBar is torn down and re-applied from settings throughfloatbar::apply_state, because an enabled bar is on screen for as long as it is enabled and nothing would ever re-show it; a disabled bar stays torn down. Since the browser process is shared, one exit fires for every window at once; per-window in-flight flags keep the concurrent rebuilds from stacking and clear themselves if a rebuild thread panics.Reveal handshake for rebuilt windows. The flyout is reopened through
flyout_window::open_or_focus, so it goes through the samevisible(false)then frontend-reveal handshake as any first build.mainis rebuilt hidden from the config and shown by the replayed surface transition; Settings re-enters its own first-build path on the default tab (the tab it showed died with the webview) at its remembered geometry. Neithermainnor Settings has a frontend-reveal handshake today (reveal_tray_panel_windowis flyout-specific), so their recovery matches their first build rather than the flyout's. If you would rather generalize the handshake per window, I am happy to do that as a follow-up.Two smaller pieces.
webview_recoverygainsdestroy_and_releasefor the rebuild threads: Tauri releases a destroyed window's label only when the event loop processesDestroyed, afterdestroy()has returned, and a rebuild issued before that fails with "a window with label…already exists". The wait compares native handles, so an open that races the teardown and rebuilds the window first ends the wait instead of timing it out against the new window (observed live: a widget click in the same instant as the kill), and it is bounded in polls rather than wall-clock time because each poll can block behind another window's build on the main thread. The flyout opener waits (bounded) for an in-flight teardown of its own window for the same reason. And the flyout'sFocused(false)handler now ignores a never-shown window: Windows reports a focus loss when a hidden window is activated without foreground rights, which happens right afterbuild(), and treating it as a dismiss cleared the pending reveal and left the rebuilt flyout invisible.Dependency.
webview2-com = "0.38"is added under[target.'cfg(windows)'.dependencies]. It is already inCargo.lockthrough wry at that exact version; the direct dependency exists only sowebview_lifecycle.rscan name the interfacestauri::webview::PlatformWebview::controller()hands out. Nothing else in the stack (wry, tauri-runtime-wry, tauri) surfacesProcessFailed. Flagging it explicitly sinceAGENTS.mdasks for confirmation on new dependencies.Related issue
Part of #410 (with #444). The flyout toggle serialization and the ErrorBoundary follow in a separate PR, as discussed there.
Affected areas
ProcessFailedhandling for every window, float bar recovery)Validation
powershell.exe -ExecutionPolicy Bypass -NoProfile -File scripts\local-check.ps1 -Format -Clippy -Rust -Tauri -Frontend— passed: fmt clean, clippy-D warningsclean on both manifests, shared Rust tests 1270 + 25, Tauri Rust tests 662 (15 new:guard_action,merge_replay,recovery_plan,response_for/describe,label_released), frontend tests 93 files / 742 on vitest 4.1.11, frontend build ok.pnpm --dir apps\desktop-tauri tauri:dev,RUST_LOG=debug), each scenario = kill the app'smsedgewebview2.exebrowser process and touch nothing afterwards unless stated:WARN … WebView2 process failed; rebuilding the window (#410) label="main" kind="BrowserProcessExited", thenmain window rebuilt270 ms later; a new HWND with a freshmsedgewebview2.exechild, visible at the same rect, real content (screenshot). App responsive afterwards (widget, shortcut, Settings).--type=rendererchild of the browser process):WARN … WebView2 render process failed; reloading the page (#410) label="main" kind="RenderProcessExited", same HWND, content back after the reload (screenshot).mainvisible: both rebuilt in the same burst; the flyout revealed by the frontend at the same anchor with real content (screenshot),mainreplayed at its rect.mainvisible and the flyout hidden: all three handled in the same burst; Settings rebuilt and reopened at its remembered geometry (screenshot),mainrebuilt and replayed, flyout torn down (flyout torn down; it will be rebuilt on next open) and rebuilt on the next widget click.mainrebuilt hidden (RebuildMain { replay: false }, new HWND, not shown), flyout torn down, Settings reopened. Nothing flashed.open_or_focusrebuilt the flyout while theProcessFailedteardown was still waiting for the label; the flyout came up with real content and the teardown returned as soon as it saw a different window under the label.mainhidden: kill and pressCtrl+Shift+Uin the same instant. The open hit the in-flight rebuild (main rebuild already in flight; deferring this open queued=true) and was replayed once it landed: the dashboard appeared at its usual rect with no second press.RebuildFloatBar→float bar torn down and re-applied from settings label="floatbar" enabled=true340 ms later; a new HWND at the same rect with a live WebView2 chain, re-subscribed, content identical to before the kill (screenshots before and after).UI / tray proof
Notes for reviewers
apply_transition_requestholdsSHELL_TRANSITION_SERIALwhile it calls window getters that are answered by the main thread, and a freshly built window receives aFocused(true)/Focused(false)pair whose handler (hide_to_tray_if_current) takes the same lock on the main thread. Run from the rebuild thread, the replay deadlocked the whole app on every rebuild of a visiblemain(global shortcut dead, no log lines).replay_on_main_threaddispatches it viarun_on_main_thread, where the tray and menu paths already run their transitions. Rule I would suggest for the codebase: never holdSHELL_TRANSITION_SERIALon a non-main thread while touching a window. The same reasoning is why the liveness probe formainworks on a cached handle instead of asking the window.mainis being rebuilt.transition_to_target/reopen_to_targetreturnOk(SurfaceMode::Hidden)and the request is queued as the replay;set_surface_modetherefore resolves with"hidden"and the flyout dismisses itself, and the dashboard appears a few hundred milliseconds later when the replay lands. Returning an error instead would keep the flyout open but surface a failure for something that is about to succeed. Happy to flip that if you prefer the error.settings_window::open_or_focusmay run on the main thread (tray menu), so unlike the flyout it cannot wait for an in-flight teardown of its window. An open landing in the few hundred milliseconds betweendestroy()and the released label goes throughreclaim_dead_window, which treats a window without a native handle as alive; that click may be dropped with a warn. Small window, no crash, mentioned for completeness.ProcessFailedhandled, dead windows are destroyed at crash time, soreclaim_dead_windowbecomes the fallback for the case where the subscription could not be made (it is best-effort and warn-logged). One observation on that fallback, not changed here: because the label is released only afterDestroyedis processed, an open issued right afterreclaim_dead_windowdestroys can still find the half-destroyed window under the label;destroy_and_releaseis the wait version if you want it there too, but it must not run on the main thread andfloatbar::installcallsshowfromsetup.Summary by CodeRabbit
Bug Fixes
Reliability
Note
Rebuild windows on WebView2
ProcessFailedand recover deadmainwindowwebview_lifecyclemodule to subscribe to WebView2ProcessFailedCOM events on Windows. Browser-process failures trigger window rebuilds and render-process failures trigger page reloads.window_recoverymodule to rebuild deadmain, Settings, flyout, and float-bar windows off-thread. It waits for Tauri labels to release and replays pending surface transitions for themainwindow.mainwindow lookups now usewindow_recovery::resolve_live_mainto defer dead or missing windows to the recovery flow.Macroscope summarized b286325.