ai gen description: Root cause 1 — The mandatory constraint removal (most critical)
In Electron 29+ / Chromium 116+, the old getUserMedia format with a mandatory: {} wrapper was removed. The capture worker was still using it:
video: { mandatory: { chromeMediaSource: 'desktop', ... } } // broke in Electron 29+
This caused getUserMedia to throw in the worker, which sent a stream-error back to the main process, which fell back to the frame loop. Fix: flat constraint format with no mandatory wrapper.
Root cause 2 — Frame loop spammed getSources() every 200ms
Once the stream backend failed, the fallback frame loop called desktopCapturer.getSources() 5× per second. On Linux via the XDG portal, each getSources() call is a new permission request → dialog every few seconds. Fix: on Linux without click capture, don't fall back to the frame loop at all — just let interval/hotkey captures take individual fresh shots.
Root cause 3 — Interval/hotkey captures bypassed the stream backend
Even when the stream backend is running, sessionCapture('interval') went straight to shoot() → grab() → getSources(). Fix: non-click triggers now pull a buffered frame from the stream backend's ring buffer (sampled every 100ms), completely avoiding getSources().
Root cause 4 — Stream backend never started on Wayland
The earlier fix made recorderWanted = false on Wayland, so the stream backend never even started. Fix: recorderWanted is now true whenever stream capture is enabled (the default), regardless of whether click detection is available.
Safety net — setPermissionCheckHandler
Electron 29+ requires an explicit permission grant for display-capture in renderer windows. Added a handler that grants all permissions (safe for a fully local/offline app like StepForge).
Windows is completely unaffected — the constraint fix is Electron-version level (affects both platforms the same), and all the Linux-specific frame-loop guards only fire when clickCaptureAvailable() returns false, which only happens on Wayland.
Confirmed cause: on battery in a power-saving plan, Windows applies Power
Throttling (EcoQoS) to background work. StepForge records with its window
hidden, so the frame-capture worker renderer (plus the GPU and screen-capture
utility processes feeding it) get CPU-throttled. The throttled worker can't
sample the screen fast enough, so every click finds no fresh pre-click frame
and falls back to a slow post-click fresh shot — producing out-of-order,
dropped steps. It only reproduced on battery; plugged in (where EcoQoS stays
off even in eco mode) it worked. The capture log showed every click detected
but every one reporting "no frame qualified", with a ~4.6s stream startup.
Fixes:
- Chromium switches (disable-background-timer-throttling,
disable-renderer-backgrounding, disable-backgrounding-occluded-windows) so
Chromium stops de-prioritising and timer-throttling the hidden worker.
- New app/win-power.js opts the OS processes out of EcoQoS via
SetProcessInformation(ProcessPowerThrottling, EXECUTION_SPEED off) and
raises them to high priority. Applied to all live Electron processes when a
session starts/resumes, and to the worker renderer the moment it is created
(before it begins streaming). Best-effort, no-op off Windows.
The earlier mouse-hook EcoQoS opt-out already fixed click *detection*; this
fixes the frame-capture side that the same throttling was breaking.
The remaining 'captured slightly after the click' reports came from the
fresh-shot fallback, which grabs the screen when the click is processed
(after it). The previous lead change made that fallback *more* likely: a
frame now had to be >=120ms before the click to qualify, so on machines
where the capture stream can't always keep a frame that old buffered, more
clicks fell through to the post-click shot.
Make the click-lead a two-tier preference instead of a hard gate in
selectFrameForClick:
1. newest frame captured at least leadMs before the click (ideal margin), else
2. newest frame captured before the click at all.
Only when no pre-click frame exists does the caller fresh-shot. leadMs is
threaded through the stream backend to the worker so both selection paths
agree. Verified end to end: frames land ~120-170ms before each click,
markers stay at 0.00%, and the 8-click burst still saves all 8.
Co-Authored-By: Claude Fable 5 <[email protected]>
Root cause of 'I clicked many times but only got two screenshots':
finishing/pausing a session called backend.stop(), which cancelled every
in-flight frame request to null. Clicks whose PNG had not finished
encoding yet were then dropped — only the first few survived.
Fixes:
- Stream backend now *drains* on stop: it stops accepting new requests but
keeps the worker alive until frames already selected for queued clicks
finish encoding. stop({ immediate: true }) keeps the old abandon-now
behavior for an unhealthy worker.
- Two-stage worker reply: a fast 'frame-selected' ack pins the pairing and
proves liveness; the slow PNG payload follows. A slow encode (seconds on
software-rendered hosts) is no longer mistaken for a dead worker, which
had been forcing the post-click fresh-shot fallback (late screenshots).
- Queued clicks carry their guide id and are stored even if the session
ends while they wait in the queue.
- The tray gesture that stops a session is discarded by matching its
recorded screen position, not a time window — a fast workflow click near
the stop is no longer collateral damage. (Replaces the earlier grace
window, which dropped whole bursts.)
- A click on a display with no ready stream resolves null so the caller
fresh-shots the correct monitor instead of returning another screen.
- STEPFORGE_CAPTURE_LOG=1 prints one line per click decision; the
second-instance handler now surfaces the running window instead of
exiting silently.
- Self-test gains a fast-burst-then-finish scenario (8/8 saved) and the
marker/coordinate checks remain at 0.00% offset.
Tests: 133 unit + all repo checks passing.
Co-Authored-By: Claude Fable 5 <[email protected]>
Implements the architecture change from ai_prompts/prompt3.md:
- New app/click-frames.js: shared timestamped frame ring + strict
click-to-frame pairing (never a frame whose grab started after the
click); legacy slack behavior kept behind capture.strictClickFrames=false.
- New stream capture backend (app/stream-backend.js + hidden worker
window): per-display desktop media streams sampled into ring buffers
and PNG-encoded entirely off the main process, so click delivery is
never starved by capture work. Auto-degrades to the legacy in-process
frame loop when streams cannot start or the worker stops answering.
- Clicks are paired with their frame at event time (eager pairing in
enqueueClickCapture); only the storing is serialized, so slow encodes
cannot skew later clicks in a fast burst.
- Linux watcher: restored event-time root coordinates from
xinput test-xi2 and merge raw/regular twin events structurally.
- Replaced the 40ms time debounce with source-aware duplicate
suppression: fast legitimate clicks are never dropped.
- New app/coords.js: physical-to-DIP conversion with multi-monitor and
scale-factor handling; Windows keeps screenToDipPoint.
- STEPFORGE_CLICK_SELFTEST end-to-end hook: 3/3 clicks become steps via
the stream backend with 0.00% marker offset on this host.
- Tests rewritten/added: strict selection, coords, stream backend,
Linux coordinate parsing, twin merge, burst clicking (126 passing).
Co-Authored-By: Claude Fable 5 <[email protected]>
Tyler
