Add Figure.timestamp to plot the GMT timestamp logo

doc/api/index.rst

@@ -34,6 +34,7 @@ Plotting map elements
     Figure.logo
     Figure.solar
     Figure.text
+    Figure.timestamp
 
 Plotting tabular data
 ~~~~~~~~~~~~~~~~~~~~~

pygmt/figure.py

@@ -510,6 +510,7 @@ def _repr_html_(self):
         subplot,
         ternary,
         text,
+        timestamp,
         velo,
         wiggle,
     )

pygmt/src/__init__.py

@@ -51,6 +51,7 @@
 from pygmt.src.surface import surface
 from pygmt.src.ternary import ternary
 from pygmt.src.text import text_ as text  # "text" is an argument within "text_"
+from pygmt.src.timestamp import timestamp
 from pygmt.src.triangulate import triangulate
 from pygmt.src.velo import velo
 from pygmt.src.which import which

pygmt/src/timestamp.py

@@ -0,0 +1,100 @@
+"""
+timestamp - Plot the GMT timestamp logo.
+"""
+from packaging.version import Version
+from pygmt.clib import Session
+from pygmt.exceptions import GMTInvalidInput
+from pygmt.helpers import build_arg_string, is_nonstr_iter
+
+__doctest_skip__ = ["timestamp"]
+
+
+def timestamp(
+    self,
+    text=None,
+    label=None,
+    justification="BL",
+    offset=("-54p", "-54p"),
+    font="Helvetica",
+    timefmt="%Y %b %d %H:%M:%S",
+):
+    """
+    Plot the GMT timestamp logo.
+
+    Parameters
+    ----------
+    text : None or str
+        If ``None``, the current UNIX time stamp is shown in the GMT timestamp
+        logo. Setting this parameter to replace the UNIX time stamp with a
+        custom text string instead. The text must be less than 64 characters.
+        *Requires GMT>=6.5.0*.
+    label : None or str
+        The text string shown after the GMT timestamp logo.
+    justification : str
+        Justification of the timestamp. *justification* is a two-character code
+        that is a combination of a horizontal (**L**(eft), **C**(enter), or
+        **R**(ight)) and a vertical (**T**(op), **M**(iddle), or **B**(ottom))
+        code.
+    offset : str or tuple
+        *offset* or (*offset_x*, *offset_y*).
+        Offset the anchor point of the timestamp by *offset_x* and *offset_y*.
+        If a single value *offset* is given, *offset_y*=*offset_x*=*offset*.
+    font : str
+        Font of the timestamp and the optional label.
+        For GMT<=6.4.0, the parameter can only change the font style.
+        For GMT>=6.5.0, the parameter can change the font style and font color.
+    timefmt : str
+        Format of the time information in the UNIX time stamp. This format is
+        parsed by the C function ``strftime``, so that virtually any text can
+        be used (even not containing any time information).
+
+    Examples
+    --------
+    >>> # Plot the GMT timestamp logo.
+    >>> import pygmt
+    >>> fig = pygmt.Figure()
+    >>> fig.timestamp()
+    >>> fig.show()
+    <IPython.core.display.Image object>
+
+    >>> # Plot the GMT timestamp logo with a custom label.
+    >>> fig = pygmt.Figure()
+    >>> fig.timestamp(label="Powered by PyGMT")
+    >>> fig.show()
+    <IPython.core.display.Image object>
+    """
+    self._preprocess()  # pylint: disable=protected-access
+
+    # Build the options passed to the "plot" module
+    kwdict = dict(T=True, U="")
+    if label is not None:
+        kwdict["U"] += f"{label}"
+    kwdict["U"] += f"+j{justification}"
+
+    # Deal with compatibility with different GMT versions
+    with Session() as lib:
+        gmt_version = lib.info["version"]
+
+    if is_nonstr_iter(offset):  # given a tuple
+        kwdict["U"] += "+o" + "/".join(f"{item}" for item in offset)
+    else:  # given a single value
+        if "/" not in offset and Version(gmt_version) <= Version("6.4.0"):
+            # Giving a single offset doesn't work in GMT <= 6.4.0.
+            # See https://github.com/GenericMappingTools/gmt/issues/7107.
+            kwdict["U"] += f"+o{offset}/{offset}"
+        else:
+            kwdict["U"] += f"+o{offset}"
+
+    # The +t modifier was added in GMT 6.5.0.
+    # See https://github.com/GenericMappingTools/gmt/pull/7127.
+    if text is not None:
+        if Version(gmt_version) <= Version("6.4.0"):
+            raise GMTInvalidInput("The parameter 'text' requires GMT>=6.5.0.")
+        kwdict["U"] += f"+t{text}"
+
+    with Session() as lib:
+        lib.call_module(
+            module="plot",
+            args=build_arg_string(kwdict)
+            + f" --FONT_LOGO={font} --FORMAT_TIME_STAMP={timefmt}",
+        )