Add support for cticks

holoviews/plotting/bokeh/element.py

@@ -40,7 +40,6 @@
     FixedTicker,
     LogTicker,
     MercatorTicker,
-    Ticker,
 )
 from bokeh.models.tools import Tool
 from packaging.version import Version
@@ -76,6 +75,7 @@
     get_axis_class,
     get_scale,
     get_tab_title,
+    get_ticker_axis_props,
     glyph_order,
     hold_policy,
     match_ax_type,
@@ -1051,28 +1051,8 @@ def _axis_properties(self, axis, key, plot, dimension=None,
             if rotation:
                 axis_props['major_label_orientation'] = np.radians(rotation)
             ticker = self.xticks if axis == 'x' else self.yticks
-            if isinstance(ticker, np.ndarray):
-                ticker = list(ticker)
-            if isinstance(ticker, Ticker):
-                axis_props['ticker'] = ticker
-            elif isinstance(ticker, int):
-                axis_props['ticker'] = BasicTicker(desired_num_ticks=ticker)
-            elif isinstance(ticker, (tuple, list)):
-                if all(isinstance(t, tuple) for t in ticker):
-                    ticks, labels = zip(*ticker)
-                    # Ensure floats which are integers are serialized as ints
-                    # because in JS the lookup fails otherwise
-                    ticks = [int(t) if isinstance(t, float) and t.is_integer() else t
-                             for t in ticks]
-                    labels = [l if isinstance(l, str) else str(l)
-                              for l in labels]
-                else:
-                    ticks, labels = ticker, None
-                if ticks and util.isdatetime(ticks[0]):
-                    ticks = [util.dt_to_int(tick, 'ms') for tick in ticks]
-                axis_props['ticker'] = FixedTicker(ticks=ticks)
-                if labels is not None:
-                    axis_props['major_label_overrides'] = dict(zip(ticks, labels))
+            if not (self._subcoord_overlaid and axis == 'y'):
+                axis_props = get_ticker_axis_props(ticker)
             elif self._subcoord_overlaid and axis == 'y':
                 ticks, labels = [], []
                 idx = 0
@@ -2470,6 +2450,11 @@ class ColorbarPlot(ElementPlot):
         #FFFFFFFF or a length 3 or length 4 tuple specifying values in
         the range 0-1 or a named HTML color.""")
 
+    cticks = param.Parameter(default=None, doc="""
+        Ticks along colorbar-axis specified as an integer, explicit list of
+        tick locations, or bokeh Ticker object. If set to None default
+        bokeh ticking behavior is applied.""")
+
     logz = param.Boolean(default=False, doc="""
          Whether to apply log scaling to the z-axis.""")
 
@@ -2513,6 +2498,9 @@ def _draw_colorbar(self, plot, color_mapper, prefix=''):
         if self.cformatter is not None:
             self.colorbar_opts.update({'formatter': wrap_formatter(self.cformatter, 'c')})
 
+        if self.cticks is not None:
+            self.colorbar_opts.update(get_ticker_axis_props(self.cticks))
+
         for tk in ['cticks', 'ticks']:
             ticksize = self._fontsize(tk, common=False).get('fontsize')
             if ticksize is not None:

holoviews/plotting/bokeh/util.py

@@ -39,12 +39,18 @@
 )
 from bokeh.models.formatters import PrintfTickFormatter, TickFormatter
 from bokeh.models.scales import CategoricalScale, LinearScale, LogScale
+from bokeh.models.tickers import (
+    BasicTicker,
+    FixedTicker,
+    Ticker,
+)
 from bokeh.models.widgets import DataTable, Div
 from bokeh.plotting import figure
 from bokeh.themes import built_in_themes
 from bokeh.themes.theme import Theme
 from packaging.version import Version
 
+from ...core import util
 from ...core.layout import Layout
 from ...core.ndmapping import NdMapping
 from ...core.overlay import NdOverlay, Overlay
@@ -1167,3 +1173,30 @@ def dtype_fix_hook(plot, element):
                 for k, v in data.items():
                     if hasattr(v, "dtype") and v.dtype.kind == "U":
                         data[k] = v.tolist()
+
+
+def get_ticker_axis_props(ticker):
+    axis_props = {}
+    if isinstance(ticker, np.ndarray):
+        ticker = list(ticker)
+    if isinstance(ticker, Ticker):
+        axis_props['ticker'] = ticker
+    elif isinstance(ticker, int):
+        axis_props['ticker'] = BasicTicker(desired_num_ticks=ticker)
+    elif isinstance(ticker, (tuple, list)):
+        if all(isinstance(t, tuple) for t in ticker):
+            ticks, labels = zip(*ticker)
+            # Ensure floats which are integers are serialized as ints
+            # because in JS the lookup fails otherwise
+            ticks = [int(t) if isinstance(t, float) and t.is_integer() else t
+                        for t in ticks]
+            labels = [l if isinstance(l, str) else str(l)
+                        for l in labels]
+        else:
+            ticks, labels = ticker, None
+        if ticks and util.isdatetime(ticks[0]):
+            ticks = [util.dt_to_int(tick, 'ms') for tick in ticks]
+        axis_props['ticker'] = FixedTicker(ticks=ticks)
+        if labels is not None:
+            axis_props['major_label_overrides'] = dict(zip(ticks, labels))
+    return axis_props

holoviews/tests/plotting/bokeh/test_elementplot.py

@@ -43,7 +43,7 @@
         xaxis = plot.handles['xaxis']
         yaxis = plot.handles['yaxis']
         self.assertEqual(fig.title.text_font_size, '24pt')
         self.assertEqual(xaxis.axis_label_text_font_size, '26px')
         self.assertEqual(yaxis.axis_label_text_font_size, '26px')
         self.assertEqual(xaxis.major_label_text_font_size, '22px')
         self.assertEqual(yaxis.major_label_text_font_size, '22px')
@@ -345,13 +345,13 @@
         plot = bokeh_renderer.get_plot(curve)
         xaxis = plot.handles['xaxis']
         self.assertEqual(xaxis.major_label_text_font_size, '6pt')
         self.assertEqual(xaxis.group_text_font_size, '18pt')
 
     def test_categorical_axis_fontsize_both(self):
         curve = Curve([('A', 1), ('B', 2)]).opts(fontsize={'xticks': 18})
         plot = bokeh_renderer.get_plot(curve)
         xaxis = plot.handles['xaxis']
         self.assertEqual(xaxis.major_label_text_font_size, '18pt')
         self.assertEqual(xaxis.group_text_font_size, '18pt')
 
     def test_cftime_transform_gregorian_no_warn(self):
@@ -885,6 +885,28 @@
         self.assertEqual(cmapper.factors, ['0', '1', '2', '3'])
         self.assertEqual(cmapper.palette, ['blue', 'red', 'green', 'purple'])
 
+    def test_cticks_int(self):
+        img = Image(np.array([[0, 1], [2, 3]])).opts(cticks=3, colorbar=True)
+        plot = bokeh_renderer.get_plot(img)
+        colorbar = plot.handles["colorbar"]
+        ticker = colorbar.ticker
+        assert ticker.desired_num_ticks == 3
+
+    def test_cticks_list(self):
+        img = Image(np.array([[0, 1], [2, 3]])).opts(cticks=[1, 2], colorbar=True)
+        plot = bokeh_renderer.get_plot(img)
+        colorbar = plot.handles["colorbar"]
+        ticker = colorbar.ticker
+        assert ticker.ticks == [1, 2]
+
+    def test_cticks_labels(self):
+        img = Image(np.array([[0, 1], [2, 3]])).opts(cticks=[(1, "A"), (2, "B")], colorbar=True)
+        plot = bokeh_renderer.get_plot(img)
+        colorbar = plot.handles["colorbar"]
+        assert colorbar.major_label_overrides == {1: "A", 2: "B"}
+        ticker = colorbar.ticker
+        assert ticker.ticks == [1, 2]
+
 
 class TestOverlayPlot(TestBokehPlot):