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fix(desktop): stamp the start mark at the anchored input event

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Blind-review round 18 (Opus xhigh) finding: 26ee8982b moved the
measure's origin to the input event's timeStamp but left the start mark
at handler-dispatch time, so the Performance panel showed the measure
beginning before its own start mark by the input delay — two different
switch durations from one instrument. The mark now carries
startTime: startedAt, pinned by asserting mark and measure share the
anchor.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Signed-off-by: Max Lampert <maxwell@squareup.com>
This commit is contained in:
Max Lampert
2026-08-25 04:06:06 -07:00
parent a355a0b1d3
commit a0a7989022
2 changed files with 13 additions and 1 deletions
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6
desktop/src/shared/lib/channelSwitchPerf.test.mjs
View File

@@ -471,6 +471,9 @@ test("the trace anchors at the input event, not handler dispatch", async () => {
globalThis.window.event = { timeStamp: performance.now() - 550 };
begin("aaaa1111aaaa1111");
delete globalThis.window.event;
const startMark = performance
.getEntriesByName("buzz:channel-switch:start")
.at(-1);
settle("aaaa1111aaaa1111");
flush();
const measure = performance
@@ -481,6 +484,9 @@ test("the trace anchors at the input event, not handler dispatch", async () => {
measure.duration >= 550,
`input delay must be inside the measure (got ${measure.duration})`,
);
// The mark and the measure must share the anchor, or the Performance
// panel shows two different switch durations for the same switch.
assert.equal(startMark?.startTime, measure.startTime);
});
});

8
desktop/src/shared/lib/channelSwitchPerf.ts
View File

@@ -280,7 +280,13 @@ export function beginChannelSwitchTrace(channelId: string): void {
performance.clearMarks(CHANNEL_SWITCH_START_MARK);
performance.clearMarks(CHANNEL_SWITCH_SETTLED_MARK);
performance.clearMeasures(CHANNEL_SWITCH_MEASURE);
performance.mark(CHANNEL_SWITCH_START_MARK, { detail: { channelId } });
// startTime keeps the mark on the same anchor as the measure — without it
// the Performance panel would show the measure starting before its own
// start mark by the input delay.
performance.mark(CHANNEL_SWITCH_START_MARK, {
detail: { channelId },
startTime: startedAt,
});
}
export function markChannelSwitchRouteCommit(channelId: string): void {