Fix DMS not set on some projections (#293)

* don't set the formatter; handle through init

* add test

* rm lon0 logic

* restore lazy loading

* more restoring

* more restoring

* replace logic with rectilinear

* update test

* update tests

* recover

* revert most changes

* reshuffle some code and rm dead code

* fix and slight shuffle

* update unittest

* mv logic back

* mv logic back

* mv logic back

* mv logic back

* mv logic back

* rm print

* don't need this anymore

* make error more helpful

Author: cvanelteren

ultraplot/axes/geo.py

@@ -1273,6 +1273,10 @@ def projection(self, map_projection):
         if not isinstance(map_projection, cls):
             raise ValueError(f"Projection must be a {cls} instance.")
         self._map_projection = map_projection
+        if hasattr(self, "_lonaxis") or hasattr(self, "_lataxis"):
+            # Update the projection of the lon and lat axes
+            self._lonaxis.get_major_formatter()._source_projection = map_projection
+            self._lataxis.get_major_formatter()._source_projection = map_projection
 
 
 class _CartopyAxes(GeoAxes, _GeoAxes):

ultraplot/tests/test_geographic.py

@@ -236,7 +236,7 @@ def test_lon0_shifts():
         # abs is taken due to north-west
         str_loc = str(abs(int(loc)))
         n = len(str_loc)
-        assert str_loc == format[:n]
+        assert str_loc == format[:n], f"Epxected: {str_loc}, got: {format[:n]}"
     assert locs[0] != 0  # we should not be a 0 anymore
     uplt.close(fig)
 
@@ -850,3 +850,27 @@ def test_consistent_range():
 
         assert np.allclose(lonview, lonlim)
         assert np.allclose(latview, latlim)
+
+
+@pytest.mark.mpl_image_compare
+def test_dms_used_for_mercator():
+    """
+    Test that DMS is used for Mercator projection
+    """
+    limit = (0.6, 113.25)
+    fig, ax = uplt.subplots(ncols=2, proj=("cyl", "merc"), share=0)
+    ax.format(land=True, labels=True, lonlocator=limit)
+    ax.format(land=True, labels=True, lonlocator=limit)
+    import matplotlib.ticker as mticker
+
+    expectations = (
+        "0°36′E",
+        "113°15′E",
+    )
+
+    for expectation, tick in zip(expectations, limit):
+        a = ax[0].gridlines_major.xformatter(tick)
+        b = ax[1].gridlines_major.xformatter(tick)
+        assert a == expectation
+        assert b == expectation
+    return fig

ultraplot/ticker.py

@@ -884,18 +884,6 @@ def __init__(self, lon0=0, *args, **kwargs):
         self.lon0 = lon0
         super().__init__(*args, **kwargs)
 
-    def __call__(self, x, pos=None):
-        """
-        Format the longitude, accounting for lon0 offset.
-        """
-        # Adjust longitude value based on lon0
-        adjusted_lon = x - self.lon0
-        # Normalize to -180 to 180 range
-        adjusted_lon = ((adjusted_lon + 180) % 360) - 180
-        print(x)
-        # Use the original formatter with the adjusted longitude
-        return super().__call__(adjusted_lon, pos)
-
 
 class LatitudeFormatter(_CartopyFormatter, LatitudeFormatter):
     """