fix(interactive.imagetool): scale spinbox decimals relative to coordi…

…nate step size

src/erlab/interactive/imagetool/controls.py

@@ -445,6 +445,7 @@ def update_content(self) -> None:
             self.spin_val[i].setRange(*self.array_slicer.lims[i])
             self.spin_val[i].setSingleStep(self.array_slicer.incs[i])
             self.spin_val[i].setValue(self.slicer_area.get_current_value(i))
+            self.spin_val[i].setDecimals(self.array_slicer.get_significant(i))
 
             self.label_dim[i].blockSignals(False)
             self.spin_idx[i].blockSignals(False)

src/erlab/interactive/imagetool/slicer.py

@@ -369,6 +369,11 @@ def values_of_dim(self, dim: Hashable) -> npt.NDArray[np.float32]:
         """
         return self._obj._coords[dim]._data.array._data  # type: ignore[union-attr]
 
+    def get_significant(self, axis: int) -> int:
+        """Return the number of significant digits for a given axis."""
+        step = self.incs[axis]
+        return int(np.clip(np.ceil(-np.log10(abs(step)) + 1), 0, None))
+
     def add_cursor(self, like_cursor: int = -1, update: bool = True) -> None:
         self._bins.append(list(self.get_bins(like_cursor)))
         new_ind = self.get_indices(like_cursor)