Public Access
jaap-jan
963cb7f670
Going back to a terminal left alone for a while found it stuck on "Reconnecting the terminal view…", and stuck is the right word: the banner stayed and nothing behind it was reconnecting. The page's whole recovery story was a setTimeout chain, and a chain is exactly what a WebView is entitled to stop running. Chromium throttles timers in a page nobody is looking at — down to once a minute once it has been hidden five minutes — and a renderer that is frozen, or reclaimed and not yet reloaded, runs none of them. So the socket drops while nobody is watching, the banner goes up, the retry is scheduled, and the retry is then the one thing not running. Three defects, each of which leaves that banner up for the rest of the page's life. ◆ NOTHING LISTENED FOR THE PAGE COMING BACK. The only thing that could clear the banner was a timer that may never fire. terminal.js now reconnects on visibilitychange, focus and online — the events that mean somebody is looking again, and the ones that cannot be throttled — cancelling the pending timer and resetting the backoff. Over a healthy socket all three do nothing, which is what makes them safe to fire as often as clicking a window does. ◆ A HANDSHAKE THAT NEVER FINISHED WAS INVISIBLE. Every retry was scheduled by a close or an error, so an attempt parked in CONNECTING — which is what a suspended renderer leaves behind — scheduled nothing at all, ever. There is now a five-second watchdog on the handshake. ◆ STALE SOCKETS SCHEDULED RETRIES, AND THAT ONE IS A LOOP RATHER THAN A STALL. connect() never detached the old socket's handlers, and the host aborts the displaced socket on takeover — TerminalDataPlane.UpgradeAsync, doing exactly what it should. That close read as a fresh failure and scheduled a retry against the socket that had just succeeded, whose own close scheduled the next: no fixed point, reconnecting every second forever with the banner up for most of it. Every handler now asks whether it is still the page's own attempt, and connect() closes what it abandons. ◆ WHICH OF THE PLATFORM BEHAVIOURS ACTUALLY BIT IS NOT ESTABLISHED, and the fix does not depend on knowing. Throttled timers, a frozen renderer and a reclaimed one all end at the same dead timer; guessing between them would have produced a narrower fix for one of the three. THE TEST RUNS terminal.js ITSELF, in a fake browser, inside dotnet test. RendererPage loads the file the shell project ships — not a transcription of its logic into C#, which would be a copy that stays correct while the page rots — into a Jint engine, one per test, over a harness that fakes a WebSocket and a clock and nothing else. Jint rather than a node script because CI would run the node one and nobody's inner loop would; the cost is that Jint is not Chromium, so this proves the page's logic and nothing about how a WebView behaves. That line is drawn in RendererPage's remark and picked up by two new manual checks, 1.10 for the desktop and 11.12a for the phone, which own the platform half. Four of the nine tests fail against the page as it stood — the stale close, the parked handshake, and the two wake-ups. Two more assert that a wake-up over a healthy socket does nothing, and pass against either version on purpose: they are what stops the cure being worse. Left alone deliberately: a socket that is open and dead shows no banner at all, because readyState still reads OPEN. That looks like a terminal that swallows what is typed, needs a liveness probe rather than a faster retry, and is written down at the end of 11.12a rather than quietly bundled in here.