Fix/sync ticks

ultraplot/axes/geo.py

@@ -898,6 +898,8 @@ def _pad_ticks(ticks: np.ndarray, vmin: float, vmax: float) -> np.ndarray:
         # giant lists of 10,000 gridline locations.
         if len(ticks) == 0:
             return ticks
+        if len(ticks) == 1:
+            return ticks
         range_ = np.max(ticks) - np.min(ticks)
         vmin = max(vmin, ticks[0] - range_)
         vmax = min(vmax, ticks[-1] + range_)
@@ -1595,6 +1597,46 @@ def __init__(self, *args: Any, **kwargs: Any) -> None:
         self._edge_lat_labels: list[mtext.Text] = []
         super().__init__(*args, **kwargs)
 
+    def _sync_shared_tick_state(
+        self,
+        which: str,
+        *,
+        copy_major_locator: bool = False,
+        copy_minor_locator: bool = False,
+        copy_major_formatter: bool = False,
+    ) -> None:
+        """
+        Copy explicit tick-state changes from this axis to shared GeoAxes siblings.
+        """
+        if which not in {"x", "y"}:
+            raise ValueError(f"Invalid axis: {which!r}")
+        if not any((copy_major_locator, copy_minor_locator, copy_major_formatter)):
+            return
+        if which == "x":
+            if self.figure._sharex < 2:
+                return
+            this_axis = self._lonaxis
+            siblings = list(self._shared_axes["x"].get_siblings(self))
+        else:
+            if self.figure._sharey < 2:
+                return
+            this_axis = self._lataxis
+            siblings = list(self._shared_axes["y"].get_siblings(self))
+        for sibling in siblings:
+            if sibling is self or not isinstance(sibling, GeoAxes):
+                continue
+            sibling_axis = sibling._lataxis if which == "y" else sibling._lonaxis
+            if copy_major_locator:
+                sibling_axis.set_major_locator(this_axis.get_major_locator())
+            if copy_minor_locator:
+                sibling_axis.set_minor_locator(this_axis.get_minor_locator())
+            if copy_major_formatter:
+                sibling_axis.set_major_formatter(this_axis.get_major_formatter())
+            if copy_major_locator or copy_major_formatter:
+                sibling._update_major_gridlines()
+            if copy_minor_locator:
+                sibling._update_minor_gridlines()
+
     @docstring._snippet_manager
     def hawkeye(
         self,
@@ -3087,6 +3129,26 @@ def format(
                 labelpad=labelpad,
                 nsteps=nsteps,
             )
+            self._sync_shared_tick_state(
+                "x",
+                copy_major_locator=_not_none(lonlocator=lonlocator, lonlines=lonlines)
+                is not None,
+                copy_minor_locator=_not_none(
+                    lonminorlocator=lonminorlocator, lonminorlines=lonminorlines
+                )
+                is not None,
+                copy_major_formatter=lonformatter is not None,
+            )
+            self._sync_shared_tick_state(
+                "y",
+                copy_major_locator=_not_none(latlocator=latlocator, latlines=latlines)
+                is not None,
+                copy_minor_locator=_not_none(
+                    latminorlocator=latminorlocator, latminorlines=latminorlines
+                )
+                is not None,
+                copy_major_formatter=latformatter is not None,
+            )
         self._format_apply_ticklen(
             lonlim=lonlim,
             latlim=latlim,

ultraplot/tests/test_geographic.py

@@ -3,6 +3,7 @@
 
 import numpy as np
 import pytest
+from matplotlib import ticker as mticker
 
 import ultraplot as uplt
 
@@ -795,6 +796,70 @@ def test_copy_locator_props():
         assert getattr(g1, prop) == getattr(g2, prop)
 
 
+def test_format_shared_ticks_sync():
+    pytest.importorskip("cartopy")
+    fig, ax = uplt.subplots(ncols=2, proj="cyl", share="all")
+    ax.format(lonlim=(100, 105), latlim=(30, 35), labels=True)
+
+    before_lon = ax[0]._get_lonticklocs()
+    before_lat = ax[0]._get_latticklocs()
+
+    ax[1].format(lonlines=2, latlines=1)
+
+    after_left_lon = ax[0]._get_lonticklocs()
+    after_left_lat = ax[0]._get_latticklocs()
+    after_right_lon = ax[1]._get_lonticklocs()
+    after_right_lat = ax[1]._get_latticklocs()
+    left_gridliner = ax[0]._gridliner_adapters["major"].gridliner
+
+    assert np.asarray(after_left_lon).shape != np.asarray(
+        before_lon
+    ).shape or not np.allclose(
+        after_left_lon,
+        before_lon,
+    )
+    assert np.asarray(after_left_lat).shape != np.asarray(
+        before_lat
+    ).shape or not np.allclose(
+        after_left_lat,
+        before_lat,
+    )
+    assert np.allclose(after_left_lon, after_right_lon)
+    assert np.allclose(after_left_lat, after_right_lat)
+    assert np.allclose(left_gridliner.xlocator.tick_values(100, 105), after_left_lon)
+    assert np.allclose(left_gridliner.ylocator.tick_values(30, 35), after_left_lat)
+
+    ax[1].format(lonminorlines=0.5, latminorlines=0.5)
+    assert np.allclose(
+        ax[0]._lonaxis.get_minorticklocs(), ax[1]._lonaxis.get_minorticklocs()
+    )
+    assert np.allclose(
+        ax[0]._lataxis.get_minorticklocs(), ax[1]._lataxis.get_minorticklocs()
+    )
+
+    formatter = mticker.FormatStrFormatter("%.1f")
+    ax[1].format(lonformatter=formatter, latformatter=formatter)
+    lonformatter = ax[1]._lonaxis.get_major_formatter()
+    latformatter = ax[1]._lataxis.get_major_formatter()
+    assert ax[0]._lonaxis.get_major_formatter() is lonformatter
+    assert ax[0]._lataxis.get_major_formatter() is latformatter
+    assert left_gridliner.xformatter is lonformatter
+    assert left_gridliner.yformatter is latformatter
+    uplt.close(fig)
+
+
+def test_sync_shared_tick_state_guards():
+    pytest.importorskip("cartopy")
+    fig, ax = uplt.subplots(ncols=2, proj="cyl")
+
+    ax[0]._sync_shared_tick_state("x")
+    ax[0]._sync_shared_tick_state("x", copy_major_locator=True)
+    ax[0]._sync_shared_tick_state("y", copy_major_locator=True)
+    with pytest.raises(ValueError, match="Invalid axis"):
+        ax[0]._sync_shared_tick_state("z", copy_major_locator=True)
+    uplt.close(fig)
+
+
 def test_turn_off_tick_labels_basemap():
     """
     Check if we can toggle the labels off for GeoAxes