[plotting] Repair png rendering with matplotlib >= 3.8.0

amotl · amotl · commit 44dc81649107 · 2026-02-27T02:29:50.000+01:00
diff --git a/CHANGES.rst b/CHANGES.rst
@@ -7,6 +7,7 @@ in progress
 ===========
 - Export: Repaired ``ggplot`` graph rendering by switching to ``plotnine``
 - Export: Repaired ``png`` rendering with modern ``pandas``
+- Export: Repaired ``png`` rendering with ``matplotlib >= 3.8.0``
 - General: Dropped support for Python 3.7
 
 .. _kotori-0.28.1:
diff --git a/kotori/io/export/util.py b/kotori/io/export/util.py
@@ -58,7 +58,7 @@ def matplotlib_locator_formatter(timedelta, span=1):
     Compute appropriate locator and formatter for renderers
     based on matplotlib, depending on designated time span.
     """
-    from matplotlib.dates import date_ticker_factory, DateFormatter
+    from matplotlib.dates import DateFormatter
     locator, formatter = date_ticker_factory(span)
 
     # http://pandas.pydata.org/pandas-docs/stable/timedeltas.html
@@ -93,6 +93,59 @@ def matplotlib_locator_formatter(timedelta, span=1):
     return locator, formatter
 
 
+def date_ticker_factory(span, tz=None, numticks=5):
+    """
+    Create a date locator with *numticks* (approx) and a date formatter
+    for *span* in days.  Return value is (locator, formatter).
+
+    `date_ticker_factory` was removed from matplotlib in version 3.8.0.
+    The recommendation is to use AutoDateLocator and AutoDateFormatter,
+    or to vendorize the code.
+
+    https://matplotlib.org/stable/api/prev_api_changes/api_changes_3.8.0.html#date-ticker-factory-removed
+    https://github.com/matplotlib/matplotlib/blob/v3.7.5/lib/matplotlib/dates.py#L1784C1-L1823C30
+    """
+    import math
+    from matplotlib.dates import (
+        DAYS_PER_MONTH, DAYS_PER_WEEK, DAYS_PER_YEAR, HOURS_PER_DAY, MINUTES_PER_DAY,
+        DateFormatter, DayLocator, HourLocator, MinuteLocator, MonthLocator, WeekdayLocator, YearLocator)
+
+    if span == 0:
+        span = 1 / HOURS_PER_DAY
+
+    mins = span * MINUTES_PER_DAY
+    hrs = span * HOURS_PER_DAY
+    days = span
+    wks = span / DAYS_PER_WEEK
+    months = span / DAYS_PER_MONTH      # Approx
+    years = span / DAYS_PER_YEAR        # Approx
+
+    if years > numticks:
+        locator = YearLocator(int(years / numticks), tz=tz)  # define
+        fmt = '%Y'
+    elif months > numticks:
+        locator = MonthLocator(tz=tz)
+        fmt = '%b %Y'
+    elif wks > numticks:
+        locator = WeekdayLocator(tz=tz)
+        fmt = '%a, %b %d'
+    elif days > numticks:
+        locator = DayLocator(interval=math.ceil(days / numticks), tz=tz)
+        fmt = '%b %d'
+    elif hrs > numticks:
+        locator = HourLocator(interval=math.ceil(hrs / numticks), tz=tz)
+        fmt = '%H:%M\n%b %d'
+    elif mins > numticks:
+        locator = MinuteLocator(interval=math.ceil(mins / numticks), tz=tz)
+        fmt = '%H:%M:%S'
+    else:
+        locator = MinuteLocator(tz=tz)
+        fmt = '%H:%M:%S'
+
+    formatter = DateFormatter(fmt, tz=tz)
+    return locator, formatter
+
+
 def make_timezone_unaware(df):
     # Please ensure that datetimes are timezone unaware before writing to Excel.
     # https://github.com/pandas-dev/pandas/pull/27129
diff --git a/test/conftest.py b/test/conftest.py
@@ -24,6 +24,13 @@
 #truncate.DEFAULT_MAX_CHARS = 9999
 
 
+@pytest.fixture(scope="session", autouse=True)
+def mask_logs():
+
+    # Tame logging of matplotlib, otherwise it would emit way too many log messages.
+    logging.getLogger("matplotlib.font_manager").setLevel(logging.INFO)
+
+
 def create_machinery(config, scope="package"):
 
     @pytest_twisted.inlineCallbacks
