Add font size traits to various classes (Fixes #1805)

Add titlesize trait to MapPanel. Add clabelsize trait to ContourTraits. Add colorbar_fontsize trait to ColorfillTraits. Add font_size trait to PlotObs.

src/metpy/plots/declarative.py

@@ -647,6 +647,15 @@ class MapPanel(Panel):
     This trait sets a user-defined title that will plot at the top center of the figure.
     """
 
+    titlesize = Union([Int(), Float(), Unicode()], allow_none=True, default_value=None)
+    titlesize.__doc__ = """An integer or string value for the font size of the title of the
+    figure.
+
+    This trait sets the font size for the title that will plot at the top center of the figure.
+    Accepts size in points or relative size. Allowed relative sizes are those of Matplotlib:
+    'xx-small', 'x-small', 'small', 'medium', 'large', 'x-large', 'xx-large'.
+    """
+
     @observe('plots')
     def _plots_changed(self, change):
         """Handle when our collection of plots changes."""
@@ -756,7 +765,7 @@ def draw(self):
 
             # Use the set title or generate one.
             title = self.title or ',\n'.join(plot.name for plot in self.plots)
-            self.ax.set_title(title)
+            self.ax.set_title(title, fontsize=self.titlesize)
             self._need_redraw = False
 
     def __copy__(self):
@@ -987,8 +996,9 @@ def draw(self):
             if getattr(self, 'handle', None) is None:
                 self._build()
             if getattr(self, 'colorbar', None) is not None:
-                self.parent.ax.figure.colorbar(
-                    self.handle, orientation=self.colorbar, pad=0, aspect=50)
+                self.parent.ax.figure.colorbar(self.handle, orientation=self.colorbar,
+                                               pad=0, aspect=50)\
+                    .ax.tick_params(labelsize=self.colorbar_fontsize)
             self._need_redraw = False
 
 
@@ -1010,6 +1020,14 @@ class ContourTraits(HasTraits):
     To plot contour labels set this trait to ``True``, the default value is ``False``.
     """
 
+    clabelsize = Union([Int(), Float(), Unicode()], allow_none=True, default_value=None)
+    clabelsize.__doc__ = """An integer, float, or string value to set the font size of labels for contours.
+
+    This trait sets the font size for labels that will plot along contour lines. Accepts
+    size in points or relative size. Allowed relative sizes are those of Matplotlib:
+    'xx-small', 'x-small', 'small', 'medium', 'large', 'x-large', 'xx-large'.
+    """
+
 
 class ColorfillTraits(HasTraits):
     """Represent common colorfill traits."""
@@ -1037,6 +1055,15 @@ class ColorfillTraits(HasTraits):
     ``None``.
     """
 
+    colorbar_fontsize = Union([Int(), Float(), Unicode()], allow_none=True, default_value=None)
+    colorbar_fontsize.__doc__ = """An integer, float, or string value to set the font size of
+    labels for the colorbar.
+
+    This trait sets the font size of labels for the colorbar. Accepts size in points or
+    relative size. Allowed relative sizes are those of Matplotlib: 'xx-small', 'x-small',
+    'small', 'medium', 'large', 'x-large', 'xx-large'.
+    """
+
 
 @exporter.export
 class ImagePlot(PlotScalar, ColorfillTraits):
@@ -1115,7 +1142,7 @@ class ContourPlot(PlotScalar, ContourTraits):
     dashdot.
     """
 
-    @observe('contours', 'linecolor', 'linewidth', 'linestyle', 'clabels')
+    @observe('contours', 'linecolor', 'linewidth', 'linestyle', 'clabels', 'clabelsize')
     def _set_need_rebuild(self, _):
         """Handle changes to attributes that need to regenerate everything."""
         # Because matplotlib doesn't let you just change these properties, we need
@@ -1131,7 +1158,7 @@ def _build(self):
                                              transform=imdata.metpy.cartopy_crs)
         if self.clabels:
             self.handle.clabel(inline=1, fmt='%.0f', inline_spacing=8,
-                               use_clabeltext=True)
+                               use_clabeltext=True, fontsize=self.clabelsize)
 
 
 @exporter.export
@@ -1431,6 +1458,10 @@ class PlotObs(HasTraits):
     plotting using the MetPy Units module, provided that units are attached to the DataFrame.
     """
 
+    font_size = Int(10)
+    font_size.__doc__ = """An integer value to set the font size of station plots. Default
+    is 10 pt."""
+
     def clear(self):
         """Clear the plot.
 
@@ -1579,7 +1610,7 @@ def _build(self):
         subset = reduce_point_density(point_locs, self.reduce_points * scale)
 
         self.handle = StationPlot(self.parent.ax, lon[subset], lat[subset], clip_on=True,
-                                  transform=ccrs.PlateCarree(), fontsize=10)
+                                  transform=ccrs.PlateCarree(), fontsize=self.font_size)
 
         for i, ob_type in enumerate(self.fields):
             field_kwargs = {}

tests/plots/test_declarative.py

@@ -1150,6 +1150,66 @@ def test_declarative_multiple_sfc_obs_change_units(ccrs):
     return pc.figure
 
 
+@pytest.mark.mpl_image_compare(remove_text=True, tolerance=0.607)
+@needs_cartopy
+def test_declarative_font_sizes():
+    """Test all font size attributes."""
+    data = xr.open_dataset(get_test_data('GFS_test.nc', as_file_obj=False))
+
+    cntr = ContourPlot()
+    cntr.data = data
+    cntr.field = 'Geopotential_height_isobaric'
+    cntr.level = 300 * units.hPa
+    cntr.time = datetime(2010, 10, 26, 12)
+    cntr.contours = list(range(0, 10000, 120))
+    cntr.linecolor = 'black'
+    cntr.linestyle = 'solid'
+    cntr.clabels = True
+    cntr.clabelsize = 18
+
+    cfill = FilledContourPlot()
+    cfill.data = data
+    cfill.field = 'Temperature_isobaric'
+    cfill.level = 300 * units.hPa
+    cfill.time = datetime(2010, 10, 26, 12)
+    cfill.contours = list(range(210, 250, 2))
+    cfill.colormap = 'BuPu'
+    cfill.colorbar = 'horizontal'
+    cfill.colorbar_fontsize = 'x-small'
+
+    data2 = parse_metar_file(get_test_data('metar_20190701_1200.txt',
+                                           as_file_obj=False), year=2019, month=7)
+    obs = PlotObs()
+    obs.data = data2
+    obs.time = datetime(2019, 7, 1, 12)
+    obs.time_window = timedelta(minutes=15)
+    obs.level = None
+    obs.fields = ['cloud_coverage', 'air_temperature', 'dew_point_temperature',
+                  'air_pressure_at_sea_level', 'current_wx1_symbol']
+    obs.plot_units = [None, 'degF', 'degF', None, None]
+    obs.locations = ['C', 'NW', 'SW', 'NE', 'W']
+    obs.formats = ['sky_cover', None, None, lambda v: format(v * 10, '.0f')[-3:],
+                   'current_weather']
+    obs.reduce_points = 3
+    obs.vector_field = ['eastward_wind', 'northward_wind']
+    obs.font_size = 7
+
+    panel = MapPanel()
+    panel.area = 'centus'
+    panel.projection = 'data'
+    panel.layers = ['coastline', 'borders', 'usstates']
+    panel.plots = [cntr, cfill, obs]
+    panel.title = '300 hPa Height and Temperature; Surface Obs'
+    panel.titlesize = 'xx-large'
+
+    pc = PanelContainer()
+    pc.size = (8, 8)
+    pc.panels = [panel]
+    pc.draw()
+
+    return pc.figure
+
+
 def test_save():
     """Test that our saving function works."""
     pc = PanelContainer()