Figure.grdview: Fix the default z-plane to the grid z minimum when plane is set to True or only facede_fill/facede_pen is set

pygmt/src/grdview.py

@@ -6,10 +6,12 @@
 from typing import Literal
 
 import xarray as xr
+from packaging.version import Version
 from pygmt._typing import PathLike
 from pygmt.alias import Alias, AliasSystem
-from pygmt.clib import Session
+from pygmt.clib import Session, __gmt_version__
 from pygmt.helpers import build_arg_list, deprecate_parameter, fmt_docstring, use_alias
+from pygmt.src.grdinfo import grdinfo
 
 __doctest_skip__ = ["grdview"]
 
@@ -116,6 +118,8 @@ def grdview(  # noqa: PLR0913
         value in the grid. However, if ``region`` was used to set *zmin/zmax* then
         *zmin* is used if it is less than the grid minimum value. Use ``facade_pen`` and
         ``facade_fill`` to control the appearance of the plane.
+        **Note**: For GMT<=6.6.0, *zmin* set in ``region`` has no effect due to a GMT
+        bug.
     facade_fill
         Fill for the frontal facade between the plane specified by ``plane`` and the
         data perimeter.
@@ -174,6 +178,18 @@ def grdview(  # noqa: PLR0913
     if plane is False and (facade_fill is not None or facade_pen is not None):
         plane = True
 
+    # Workaround for GMT bug https://github.com/GenericMappingTools/gmt/pull/8838
+    # Fix the plane value to be the grid minimum if plane=True.
+    # Notes:
+    # 1. It's the minimum of the grid, not a subset of the grid defined by `region'.
+    # 2. The GMT docs says "if -R was used to set zmin/zmax then we use that value if
+    #    it is less than the grid minimum value.". We can't add a workaround for this
+    #    case since we can't parse zmin/zmax from `region' if `region' was set in
+    #    previous plotting commands.
+    # TODO(GMT>6.6.0): Remove this workaround.
+    if Version(__gmt_version__) <= Version("6.6.0") and plane is True:
+        plane = grdinfo(grid, per_column=True).split()[4]
+
     aliasdict = AliasSystem(
         Jz=Alias(zscale, name="zscale"),
         JZ=Alias(zsize, name="zsize"),

pygmt/tests/baseline/test_grdview_facadepen_default_plane.png.dvc

@@ -1,5 +1,5 @@
 outs:
-- md5: cfff4879fbe7ab03d8a304b2622b9782
-  size: 26208
+- md5: aa725f7d05462e7d272cf7045a7c9913
+  size: 32037
   hash: md5
   path: test_grdview_facadepen_default_plane.png