Files
LEDMatrix/test/test_display_dirty_tracking.py
T
ChuckandClaude Opus 5.5 98ebc859e0 fix(display): only mtime-touch a snapshot frame that is actually on disk
From review (CodeRabbit): the digest was recorded when a frame was queued,
so while the writer hadn't saved it yet, an unchanged frame could take
the TOUCH path and refresh the mtime of the older file on disk. Track the
saved frame's digest separately (set by the writer and the inline path
after a successful save) and write, not touch, when it isn't the current
frame.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-09-24 18:39:49 -04:00

504 lines
21 KiB
Python

"""Tests for update_display dirty tracking (src/display_manager.py).
Runs against RGBMatrixEmulator (EMULATOR=true), exercising the REAL
DisplayManager — not a mock — so the skip logic, its invalidation hooks,
and the kill switch are verified off-Pi.
The invariants:
- identical frames are pushed exactly once (SwapOnVSync not re-called)
- ANY pixel change pushes
- clear() and set_brightness() invalidate (the two paths that alter panel
state outside the digest's view)
- the kill switch (display.dirty_tracking: false) restores always-push
"""
import os
import sys
import time
os.environ["EMULATOR"] = "true"
import pytest
sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
@pytest.fixture(scope="module")
def dm(tmp_path_factory):
"""One real DisplayManager on the emulator (it's a process singleton)."""
from src.display_manager import DisplayManager
DisplayManager._instance = None
manager = DisplayManager({
"display": {
"hardware": {"rows": 32, "cols": 64, "chain_length": 2,
"parallel": 1, "brightness": 90},
"runtime": {"gpio_slowdown": 0},
},
}, suppress_test_pattern=True)
# DisplayManager defaults _snapshot_path to the fixed /tmp/led_matrix_preview.png
# that the web UI reads. That path is shared by every pytest process on the
# machine, so two concurrent runs -- CI shards, a second worktree, a agent
# running the suite alongside -- write over each other's snapshot and the
# mtime assertions below stop meaning anything. Point it somewhere unique to
# this session; the individual tests that care still override it further.
manager._snapshot_path = str(
tmp_path_factory.mktemp("dirty_tracking") / "led_matrix_preview.png")
# _setup_matrix() swallows every construction failure and falls back to
# matrix=None, so a broken environment reaches the tests as fifteen
# identical "'NoneType' object has no attribute 'SwapOnVSync'" errors that
# name neither this fixture nor the real cause. Fail here instead, once,
# and say where to look.
if manager.matrix is None:
pytest.fail(
"DisplayManager fell back to matrix=None: RGBMatrix construction "
"raised (the 'Failed to initialize RGB Matrix' log line above "
"carries the reason). Known causes: the emulator adapter losing a "
"fixed TCP port to another process -- see pytest_configure in "
"test/conftest.py, which pins the port-free 'raw' adapter -- or a "
"patch('src.display_manager.RGBMatrix') leaked from an earlier "
"test module.")
yield manager
DisplayManager._instance = None
class _SwapSpy:
"""Counts SwapOnVSync calls through the real matrix object."""
def __init__(self, matrix):
self.matrix = matrix
self.count = 0
self.last_frame_hold = None
self._orig = matrix.SwapOnVSync
def __enter__(self):
def counting(canvas, *args):
# *args carries framerate_fraction, which display_manager passes so
# a frame can be held for several refreshes. Signature must match
# the real binding or the spy hides a TypeError as a failed push.
self.count += 1
self.last_frame_hold = args[0] if args else 1
return self._orig(canvas, *args)
self.matrix.SwapOnVSync = counting
return self
def __exit__(self, *exc):
self.matrix.SwapOnVSync = self._orig
class TestDirtyTracking:
def test_identical_frames_push_once(self, dm):
dm.draw.rectangle([0, 0, 10, 10], fill=(255, 0, 0))
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
dm.update_display()
dm.update_display()
assert spy.count == 1
def test_pixel_change_pushes(self, dm):
dm.update_display()
with _SwapSpy(dm.matrix) as spy:
dm.draw.point((5, 5), fill=(0, 255, 0))
dm.update_display()
dm.update_display() # unchanged again
assert spy.count == 1
def test_clear_invalidates(self, dm):
dm.draw.rectangle([0, 0, 20, 20], fill=(0, 0, 255))
dm.update_display()
dm.clear() # writes to the matrix directly; digest must reset
with _SwapSpy(dm.matrix) as spy:
dm.update_display() # black frame after clear must still push
assert spy.count == 1
def test_brightness_change_forces_push(self, dm):
dm.draw.rectangle([0, 0, 20, 20], fill=(200, 200, 200))
dm.update_display()
with _SwapSpy(dm.matrix) as spy:
dm.update_display() # identical -> skipped
assert spy.count == 0
dm.set_brightness(40) # dim schedule scenario
dm.update_display() # same image, new brightness -> push
assert spy.count == 1
dm.set_brightness(90)
def test_snapshot_still_written_on_skip(self, dm, tmp_path):
"""The web preview mirror must keep working through skipped panel
pushes: _write_snapshot_if_due() still runs on the dirty-tracking
skip path and applies its own write/touch policy rather than being
bypassed entirely (see src/common/snapshot_policy.py — an unchanged
frame is touched, not re-encoded, once TOUCH_INTERVAL elapses)."""
dm._snapshot_path = str(tmp_path / "snap.png")
dm._last_snapshot_ts = 0.0
dm._last_snapshot_touch_ts = 0.0
dm._last_snapshot_digest = None
dm.draw.rectangle([0, 0, 30, 8], fill=(255, 255, 0))
dm.update_display() # push + snapshot write (first frame)
assert os.path.exists(dm._snapshot_path)
# Backdate the file so the "was it bumped?" check below cannot be
# defeated by filesystem mtime granularity -- on Windows two writes in
# the same tick get identical timestamps, which made this test fail
# roughly two runs in three regardless of the code under test.
os.utime(dm._snapshot_path, (time.time() - 60, time.time() - 60))
first_mtime = os.path.getmtime(dm._snapshot_path)
# Age the write/touch bookkeeping past TOUCH_INTERVAL so the next
# identical frame is due for a touch, then push it again: dirty
# tracking must skip the panel write, but the snapshot mirror must
# still get its mtime bumped so the health check doesn't go stale.
from src.common import snapshot_policy
stale_ts = time.time() - snapshot_policy.TOUCH_INTERVAL - 1.0
dm._last_snapshot_ts = stale_ts
dm._last_snapshot_touch_ts = stale_ts
with _SwapSpy(dm.matrix) as spy:
dm.update_display() # identical frame -> panel push skipped
assert spy.count == 0
assert os.path.getmtime(dm._snapshot_path) > first_mtime
class TestScrollLock:
"""Dirty tracking must not skip the panel push while a scroll is running.
SwapOnVSync is what paces the render loop, so skipping it also skips the
wait for the panel. A duplicate frame therefore returns early -- ~8ms
instead of ~10ms on a 100Hz panel -- which advances the strip only 0.8px
instead of 1.0px, which makes the NEXT frame more likely to be a duplicate
too. That is self-sustaining: measured at ~20% duplicate frames mid-scroll
on the odds ticker against essentially zero on a lighter plugin with
identical scroll settings. Pushing an identical frame costs one canvas
copy; falling out of vsync lock costs smooth motion.
"""
def test_identical_frames_still_push_while_scrolling(self, dm):
dm.draw.rectangle([0, 0, 12, 12], fill=(0, 0, 255))
dm.update_display()
dm.set_scrolling_state(True)
try:
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
dm.update_display()
dm.update_display()
assert spy.count == 3, "scrolling must stay locked to the panel"
finally:
dm.set_scrolling_state(False)
def test_identical_frames_are_skipped_when_not_scrolling(self, dm):
"""The optimisation still applies to static content."""
dm.set_scrolling_state(False)
dm.draw.rectangle([0, 0, 14, 14], fill=(255, 0, 255))
dm.update_display()
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
dm.update_display()
assert spy.count == 0
def test_stale_scrolling_state_stops_forcing_pushes(self, dm):
"""A plugin that stops scrolling without saying so must not pin the
panel into always-push forever. is_currently_scrolling() expires on
its own inactivity threshold, and the skip has to come back with it."""
dm.draw.rectangle([0, 0, 16, 16], fill=(0, 255, 255))
dm.update_display()
dm.set_scrolling_state(True)
try:
# Backdate the activity marker past the inactivity threshold.
dm._scrolling_state['last_scroll_activity'] = (
time.time() - dm._scrolling_state['scroll_inactivity_threshold'] - 1.0)
assert dm.is_currently_scrolling() is False
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
dm.update_display()
assert spy.count == 0
finally:
dm.set_scrolling_state(False)
class TestKillSwitch:
def test_dirty_tracking_can_be_disabled(self, dm):
dm._dirty_tracking_enabled = False
try:
dm.draw.rectangle([0, 0, 10, 10], fill=(1, 2, 3))
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
dm.update_display()
dm.update_display()
assert spy.count == 3 # always-push, exactly the old behavior
finally:
dm._dirty_tracking_enabled = True
dm._last_pushed_digest = None
def test_config_flag_wires_through(self):
from src.display_manager import DisplayManager
DisplayManager._instance = None
try:
manager = DisplayManager({
"display": {
"hardware": {"rows": 32, "cols": 64, "chain_length": 1,
"parallel": 1},
"runtime": {"gpio_slowdown": 0},
"dirty_tracking": False,
},
}, suppress_test_pattern=True)
assert manager._dirty_tracking_enabled is False
finally:
DisplayManager._instance = None
if __name__ == "__main__":
sys.exit(pytest.main([__file__, "-v"]))
class TestFrameHold:
"""Holding a frame for N refreshes is how a scroll runs slower than one
pixel per refresh without fractional pixel positions."""
def test_hold_reaches_swap_on_vsync(self, dm):
dm.set_scrolling_state(True)
dm.set_frame_hold(3)
try:
dm.draw.rectangle([0, 0, 9, 9], fill=(120, 0, 200))
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
assert spy.count == 1
assert spy.last_frame_hold == 3
finally:
dm.set_scrolling_state(False)
def test_default_is_every_refresh(self, dm):
dm.set_scrolling_state(True)
try:
dm.draw.rectangle([0, 0, 11, 11], fill=(0, 120, 200))
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
assert spy.last_frame_hold == 1
finally:
dm.set_scrolling_state(False)
def test_hold_resets_when_scrolling_stops(self, dm):
"""One plugin's pacing must not leak into whatever is on screen next."""
dm.set_scrolling_state(True)
dm.set_frame_hold(5)
dm.set_scrolling_state(False)
dm.set_scrolling_state(True)
try:
dm.draw.rectangle([0, 0, 13, 13], fill=(200, 120, 0))
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
assert spy.last_frame_hold == 1
finally:
dm.set_scrolling_state(False)
@pytest.mark.parametrize("bad,expected", [(0, 1), (-4, 1), (None, 1), ("x", 1)])
def test_unusable_holds_are_ignored_or_floored(self, dm, bad, expected):
dm.set_frame_hold(bad)
assert dm._frame_hold == expected
class TestFrameHoldLifetime:
"""The hold must last exactly as long as the scroll that asked for it.
Plugins share one display manager. A hold applied at plugin construction is
wiped the moment any *other* plugin finishes scrolling, so by the time the
first plugin renders it is back to one pixel per refresh -- the speed reads
correct in the log and is wrong on the panel.
"""
def test_scrolling_state_carries_the_hold(self, dm):
dm.set_scrolling_state(True, frame_hold=4)
try:
dm.draw.rectangle([0, 0, 7, 7], fill=(10, 200, 10))
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
assert spy.last_frame_hold == 4
finally:
dm.set_scrolling_state(False)
def test_a_scroll_that_times_out_does_not_strand_a_hold(self, dm):
"""The hold must go when the state does, however the scroll ended.
set_scrolling_state(False) is the polite exit. The other one is
is_currently_scrolling() deciding, after scroll_inactivity_threshold
of silence, that the scroll is over -- which is what happens when the
rotation moves on mid-scroll or a plugin is torn down. That path used
to clear the flag and keep the hold, so every later plugin, scrolling
or static, was presented at refresh/N by whoever scrolled last.
"""
dm.set_scrolling_state(True, frame_hold=5)
# Age the scroll past the inactivity threshold rather than sleeping.
dm._scrolling_state['last_scroll_activity'] -= (
dm._scrolling_state['scroll_inactivity_threshold'] + 1.0)
assert dm.is_currently_scrolling() is False
dm.draw.rectangle([0, 0, 5, 5], fill=(10, 10, 200))
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
assert spy.last_frame_hold == 1, (
"a timed-out scroll left its frame hold behind; the next plugin "
"is being presented at a fraction of the refresh rate")
def test_another_plugin_stopping_does_not_strand_a_hold(self, dm):
dm.set_scrolling_state(True, frame_hold=3)
dm.set_scrolling_state(False) # some other plugin finishes
dm.set_scrolling_state(True) # a plugin that wants no hold
try:
dm.draw.rectangle([0, 0, 6, 6], fill=(200, 10, 10))
with _SwapSpy(dm.matrix) as spy:
dm.update_display()
assert spy.last_frame_hold == 1
finally:
dm.set_scrolling_state(False)
def test_default_keeps_previous_behaviour(self, dm):
"""Callers that never heard of frame holds get one frame per refresh."""
dm.set_scrolling_state(True)
try:
assert dm._frame_hold == 1
finally:
dm.set_scrolling_state(False)
class TestSnapshotOffRenderThread:
"""Mid-scroll, the preview PNG is encoded off the render thread.
At 512x64 the encode takes 12-14ms on a Pi 4 -- longer than a refresh --
so doing it inline made the next swap miss its vsync five times a second
whenever the web preview was open.
"""
def _record_saves(self, dm, monkeypatch):
import threading
threads = []
done = threading.Event()
real = dm._save_snapshot
def recording(image):
threads.append(threading.current_thread().name)
real(image)
done.set()
monkeypatch.setattr(dm, "_save_snapshot", recording)
return threads, done
def _due(self, dm, tmp_path, colour):
dm._snapshot_path = str(tmp_path / "snap.png")
dm._last_snapshot_ts = 0.0
dm._last_snapshot_touch_ts = 0.0
dm._last_snapshot_digest = None
dm.draw.rectangle([0, 0, 10, 4], fill=colour)
def test_scrolling_frames_are_encoded_on_the_writer_thread(
self, dm, tmp_path, monkeypatch):
import threading
threads, done = self._record_saves(dm, monkeypatch)
self._due(dm, tmp_path, (0, 255, 255))
dm.set_scrolling_state(True)
try:
dm.update_display()
assert done.wait(5), "the snapshot writer never wrote the frame"
finally:
dm.set_scrolling_state(False)
assert threads == ["snapshot-writer"]
assert threads[0] != threading.current_thread().name
assert os.path.exists(dm._snapshot_path)
def test_a_failed_background_write_is_retried_not_touched(
self, dm, tmp_path, monkeypatch):
# Queuing records the frame as written. If the writer then fails, an
# unchanged frame must be written again, not mtime-touched: touching
# would make a stale preview look healthy.
import threading
import time
failed = threading.Event()
def failing(image):
failed.set()
raise OSError("disk full")
monkeypatch.setattr(dm, "_save_snapshot", failing)
self._due(dm, tmp_path, (0, 255, 0))
dm.set_scrolling_state(True)
try:
dm.update_display()
assert failed.wait(5)
deadline = time.time() + 5
while dm._last_snapshot_digest is not None and time.time() < deadline:
time.sleep(0.01)
finally:
dm.set_scrolling_state(False)
assert dm._last_snapshot_digest is None
def test_a_frame_not_yet_on_disk_is_written_not_touched(
self, dm, tmp_path, monkeypatch):
# The digest is recorded when a frame is queued. Until the writer has
# saved it, an unchanged frame must not mtime-touch the older file on
# disk into looking current.
import zlib
from src.common import snapshot_policy
touched, saved = [], []
self._due(dm, tmp_path, (9, 9, 9))
digest = zlib.adler32(dm.image.tobytes())
dm._last_snapshot_digest = digest # queued earlier...
dm._saved_snapshot_digest = 12345 # ...but an older frame is on disk
monkeypatch.setattr(snapshot_policy, "decide",
lambda *a, **k: snapshot_policy.SnapshotAction.TOUCH)
monkeypatch.setattr(os, "utime", lambda *a, **k: touched.append(a))
monkeypatch.setattr(dm, "_save_snapshot", lambda image: saved.append(image))
dm.set_scrolling_state(False)
dm._write_snapshot_if_due(digest)
assert touched == []
assert len(saved) == 1
assert dm._saved_snapshot_digest == digest
# Once it is on disk, the same frame is only touched.
dm._write_snapshot_if_due(digest)
assert len(touched) == 1 and len(saved) == 1
def test_a_static_frame_lands_after_a_queued_one_still_being_written(
self, dm, tmp_path, monkeypatch):
# The last frame of a scroll can still be encoding when the first
# static frame is due; the older one must not land on top.
import threading
written, started, release = [], threading.Event(), threading.Event()
real = dm._save_snapshot
def slow_then_record(image):
if threading.current_thread().name == "snapshot-writer":
started.set()
release.wait(5)
written.append((threading.current_thread().name, image.getpixel((0, 0))))
real(image)
monkeypatch.setattr(dm, "_save_snapshot", slow_then_record)
self._due(dm, tmp_path, (0, 0, 255))
dm.set_scrolling_state(True)
dm.update_display() # queued: the writer blocks mid-write
assert started.wait(5)
dm.set_scrolling_state(False)
self._due(dm, tmp_path, (255, 0, 0))
static = threading.Thread(target=dm.update_display)
static.start()
static.join(0.2)
assert static.is_alive(), "the static save must wait for the write in flight"
release.set()
static.join(5)
assert [colour for _, colour in written] == [(0, 0, 255), (255, 0, 0)]
def test_cleanup_stops_the_writer(self, dm, tmp_path, monkeypatch):
threads, done = self._record_saves(dm, monkeypatch)
self._due(dm, tmp_path, (0, 255, 255))
dm.set_scrolling_state(True)
dm.update_display()
assert done.wait(5)
writer = dm._snapshot_thread
dm.set_scrolling_state(False)
dm._stop_snapshot_writer()
writer.join(2)
assert not writer.is_alive()
def test_static_frames_are_still_written_inline(
self, dm, tmp_path, monkeypatch):
import threading
threads, _ = self._record_saves(dm, monkeypatch)
self._due(dm, tmp_path, (255, 0, 255))
dm.set_scrolling_state(False)
dm.update_display()
assert threads == [threading.current_thread().name]