fix(display): a WiFi notice preempts the current screen and Vegas yields to it (#712)

A WiFi notice preempts the current screen within about a second (frame loops, post-loop check, make-up dwell), and an interrupted Vegas iteration that yielded for a notice ends the pass so the notice shows next. Goldens: wifi_notice, vegas. First of three run-loop fixes (#712, #713, #714), pre-tested together.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/_run_loop_harness.py

@@ -766,7 +766,14 @@ def reduce_trace(events, horizon: float) -> Dict[str, Any]:
     rows = []
     for i, screen in enumerate(screens):
         end = screens[i + 1]["t"] if i + 1 < len(screens) else horizon
-        exit_reason = screen["exit"] or ("horizon" if i + 1 == len(screens) else "duration")
+        nxt = screens[i + 1] if i + 1 < len(screens) else None
+        # A WiFi notice logs no event at the moment it takes the panel (the
+        # file is written earlier), so a screen followed by one is labelled
+        # "wifi". Its duration column shows whether it was cut short.
+        exit_reason = screen["exit"] or (
+            "horizon" if nxt is None
+            else "wifi" if nxt["mode"] == "<wifi>" and screen["mode"] != "<wifi>"
+            else "duration")
         rows.append([screen["t"], screen["mode"], round(end - screen["t"], 3),
                      exit_reason, screen["frames"], screen["clear"]])
     return {"screens": rows, "events": notable}

test/fixtures/run_loop_golden/vegas.json

@@ -10,9 +10,9 @@
     [150.263, "clock", 20.0, "duration", 20, true],
     [170.263, "clock", 5.0, "on-demand-expired", 5, true],
     [175.263, "<vegas>", 24.959, "vegas-interrupt", 3120, null],
-    [200.222, "clock", 20.0, "duration", 20, true],
-    [220.222, "<vegas>", 30.008, "duration", 3751, null],
-    [250.23, "<vegas>", 9.77, "horizon", 1222, null]
+    [200.222, "<wifi>", 3.0, "duration", 6, null],
+    [203.222, "<vegas>", 30.008, "duration", 3751, null],
+    [233.23, "<vegas>", 26.77, "horizon", 3347, null]
   ],
   "events": [
     [70.255, "vegas-live"],

test/fixtures/run_loop_golden/wifi_notice.json

@@ -1,13 +1,15 @@
 {
   "screens": [
     [0.0, "clock", 20.0, "duration", 20, false],
-    [20.0, "weather", 20.0, "duration", 20, true],
-    [40.0, "clock", 20.0, "on-demand-start", 20, true],
-    [60.0, "clock", 20.0, "on-demand-expired", 20, true],
+    [20.0, "weather", 5.0, "wifi", 6, true],
+    [25.0, "<wifi>", 5.0, "duration", 10, null],
+    [30.0, "weather", 20.0, "duration", 20, true],
+    [50.0, "clock", 20.0, "on-demand-start", 20, true],
+    [70.0, "clock", 10.0, "on-demand-expired", 10, true],
     [80.0, "<wifi>", 15.0, "duration", 30, null],
-    [95.0, "weather", 20.0, "duration", 20, true],
-    [115.0, "clock", 20.0, "duration", 20, true],
-    [135.0, "weather", 15.0, "horizon", 15, true]
+    [95.0, "clock", 20.0, "duration", 20, true],
+    [115.0, "weather", 20.0, "duration", 20, true],
+    [135.0, "clock", 15.0, "horizon", 15, true]
   ],
   "events": [
     [25.0, "wifi-file", "Connected to HomeNet"],

test/test_run_loop_golden.py

@@ -148,8 +148,8 @@ def scenario_schedule(h: RunLoopHarness):
 def scenario_wifi_notice(h: RunLoopHarness):
     h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
     h.add_plugin(FakePlugin("weather", ["weather"], duration=20))
-    # Posted mid-screen and expired before the screen ends: never shown,
-    # because the notice is only checked between screens.
+    # Posted mid-screen: it preempts the screen at its next frame, stays up
+    # until it expires, and the interrupted mode then comes back in full.
     h.wifi_message(25, "Connected to HomeNet", duration=5)
     # While on-demand is active the notice waits.
     h.on_demand_request(60, "w1", plugin_id="clock", duration=20)

test/test_wifi_notice_preemption.py

@@ -0,0 +1,130 @@
+"""A WiFi notice preempts the current screen promptly and stays up.
+
+It used to be checked only between screens, so a notice shorter than the
+screen it was posted during expired unseen, and Vegas yielding for one went
+on to a rotation screen instead of the notice. Runs the real run() loop on
+the fake clock of test/_run_loop_harness.py.
+"""
+
+import os
+
+os.environ.setdefault("EMULATOR", "true")
+
+from test._run_loop_harness import FakePlugin, RunLoopHarness  # noqa: E402
+
+
+def _rows(trace):
+    return [tuple(row[:4]) for row in trace["screens"]]
+
+
+def _wifi_rows(trace):
+    return [row for row in trace["screens"] if row[1] == "<wifi>"]
+
+
+def test_notice_preempts_a_static_screen_and_the_mode_resumes(tmp_path):
+    h = RunLoopHarness(tmp_path, horizon=70)
+    h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
+    h.add_plugin(FakePlugin("weather", ["weather"], duration=20))
+    h.wifi_message(25.3, "Connected to HomeNet", duration=5)
+    trace = h.run()
+
+    (wifi,) = _wifi_rows(trace)
+    # Within about a second of being posted (the 1 Hz loop's next frame),
+    # and up until it expires at 30.3.
+    assert 25.3 <= wifi[0] <= 26.3
+    assert wifi[0] + wifi[2] >= 30.3
+    rows = _rows(trace)
+    i = rows.index(tuple(wifi[:4]))
+    assert rows[i - 1][1] == "weather" and rows[i - 1][3] == "wifi"
+    # The interrupted screen comes back in full; the rotation is not skipped.
+    assert rows[i + 1][1:3] == ("weather", 20.0)
+    assert rows[i + 2][1] == "clock"
+
+
+def test_notice_preempts_a_high_fps_screen(tmp_path):
+    h = RunLoopHarness(tmp_path, horizon=60)
+    h.add_plugin(FakePlugin("ticker", ["ticker"], duration=30, enable_scrolling=True))
+    h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
+    h.wifi_message(10.0, "AP mode on", duration=4)
+    trace = h.run()
+
+    (wifi,) = _wifi_rows(trace)
+    assert 10.0 <= wifi[0] <= 11.0
+    assert wifi[0] + wifi[2] >= 14.0
+    assert trace["screens"][0][1:4] == ["ticker", wifi[0], "wifi"]
+
+
+def test_notice_cuts_the_make_up_dwell_short(tmp_path):
+    # flaky returns False after its first frame, so the rest of its screen
+    # is a make-up dwell rather than a frame loop.
+    h = RunLoopHarness(tmp_path, horizon=40)
+    h.add_plugin(FakePlugin("flaky", ["flaky"], duration=20, first_frame_only=True))
+    h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
+    h.wifi_message(8.0, "Connected to HomeNet", duration=5)
+    trace = h.run()
+
+    (wifi,) = _wifi_rows(trace)
+    assert 8.0 <= wifi[0] <= 9.0
+    assert wifi[0] + wifi[2] >= 13.0
+    rows = _rows(trace)
+    i = rows.index(tuple(wifi[:4]))
+    # flaky was cut short, so it comes back rather than being rotated past.
+    assert rows[i + 1][1] == "flaky"
+
+
+def test_a_screen_that_ran_its_full_time_is_not_repeated(tmp_path):
+    # Posted just before clock's 20 s are up: clock ends on time, the notice
+    # shows, and the rotation moves on to weather rather than clock again.
+    h = RunLoopHarness(tmp_path, horizon=50)
+    h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
+    h.add_plugin(FakePlugin("weather", ["weather"], duration=20))
+    h.wifi_message(19.5, "Connected to HomeNet", duration=5)
+    trace = h.run()
+
+    rows = _rows(trace)
+    assert rows[0] == (0.0, "clock", 20.0, "wifi")
+    assert rows[1][1] == "<wifi>"
+    assert rows[2][1] == "weather"
+
+
+def test_on_demand_still_outranks_the_notice(tmp_path):
+    h = RunLoopHarness(tmp_path, horizon=80)
+    h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
+    h.add_plugin(FakePlugin("weather", ["weather"], duration=20))
+    h.on_demand_request(5, "o1", plugin_id="weather", duration=30)
+    h.wifi_message(15, "AP mode on", duration=30)
+    trace = h.run()
+
+    (wifi,) = _wifi_rows(trace)
+    # Held back until the on-demand session expires at about t=35.
+    assert wifi[0] >= 35.0
+    on_demand = [r for r in trace["screens"] if r[1] == "weather" and r[0] < 35]
+    assert on_demand and all(r[3] != "wifi" for r in on_demand[:-1])
+
+
+def test_vegas_yields_to_the_notice_then_resumes(tmp_path):
+    h = RunLoopHarness(tmp_path, horizon=80)
+    h.add_plugin(FakePlugin("clock", ["clock"], duration=20))
+    h.enable_vegas(cycle=30)
+    h.wifi_message(40, "Connected to HomeNet", duration=3)
+    trace = h.run()
+
+    rows = _rows(trace)
+    i = next(n for n, row in enumerate(rows) if row[3] == "vegas-interrupt")
+    assert rows[i][1] == "<vegas>" and 40.0 <= rows[i][0] + rows[i][2] <= 41.0
+    # The notice is what shows next, for its whole 3 s, and Vegas follows.
+    assert rows[i + 1][1] == "<wifi>"
+    assert rows[i + 1][0] + rows[i + 1][2] >= 43.0
+    assert rows[i + 2][1] == "<vegas>"
+    assert "clock" not in [row[1] for row in rows[i:]]
+
+
+def test_pending_check_ignores_a_cached_notice_that_has_expired(tmp_path):
+    h = RunLoopHarness(tmp_path, horizon=10)
+    dc = h.controller
+    dc._check_wifi_status_message = lambda: {"message": "x", "expires_at": 0.0}
+    assert not dc._wifi_notice_pending()
+    dc._check_wifi_status_message = lambda: {"message": "x", "expires_at": float("inf")}
+    assert dc._wifi_notice_pending()
+    dc.on_demand_active = True
+    assert not dc._wifi_notice_pending()