Improved support for style mapping constant values (#3578)

holoviews/plotting/bokeh/element.py

@@ -23,7 +23,7 @@
 from bokeh.models.widgets import Panel, Tabs
 from bokeh.plotting.helpers import _known_tools as known_tools
 
-from ...core import DynamicMap, CompositeOverlay, Element, Dimension
+from ...core import DynamicMap, CompositeOverlay, Element, Dimension, Dataset
 from ...core.options import abbreviated_exception, SkipRendering
 from ...core import util
 from ...element import Graph, VectorField, Path, Contours, Tiles
@@ -953,16 +953,18 @@ def _apply_transforms(self, element, data, ranges, style, group=None):
                     'as not all dimensions could be resolved.' % (k, v))
                 continue
 
-            if len(v.ops) == 0 and v.dimension in self.overlay_dims:
-                val = self.overlay_dims[v.dimension]
+            if v.dimension in self.overlay_dims:
+                ds = Dataset({d.name: v for d, v in self.overlay_dims.items()},
+                             list(self.overlay_dims))
+                val = v.apply(ds, ranges=ranges, flat=True)[0]
             elif isinstance(element, Path) and not isinstance(element, Contours):
                 val = np.concatenate([v.apply(el, ranges=ranges, flat=True)[:-1]
                                       for el in element.split()])
             else:
                 val = v.apply(element, ranges=ranges, flat=True)
 
             if (not util.isscalar(val) and len(util.unique_array(val)) == 1 and
-                (not 'color' in k or validate('color', val))):
+                ((not 'color' in k or validate('color', val)) or k in self._nonvectorized_styles)):
                 val = val[0]
 
             if not util.isscalar(val):

holoviews/plotting/mpl/element.py

@@ -558,8 +558,10 @@ def _apply_transforms(self, element, ranges, style):
                     % (k, v))
                 continue
 
-            if len(v.ops) == 0 and v.dimension in self.overlay_dims:
-                val = self.overlay_dims[v.dimension]
+            if v.dimension in self.overlay_dims:
+                ds = Dataset({d.name: v for d, v in self.overlay_dims.items()},
+                             list(self.overlay_dims))
+                val = v.apply(ds, ranges=ranges, flat=True)[0]
             elif type(element) is Path:
                 val = np.concatenate([v.apply(el, ranges=ranges, flat=True)[:-1]
                                       for el in element.split()])

holoviews/tests/plotting/bokeh/testcurveplot.py

@@ -9,6 +9,7 @@
 from holoviews.element import Curve
 from holoviews.plotting.util import rgb2hex
 from holoviews.streams import PointerX
+from holoviews.util.transform import dim
 
 from .testplot import TestBokehPlot, bokeh_renderer
 
@@ -377,3 +378,55 @@ def test_curve_line_width_op(self):
                        vdims=['y', 'linewidth']).options(line_width='linewidth')
         with self.assertRaises(Exception):
             bokeh_renderer.get_plot(curve)
+
+    def test_curve_style_mapping_ndoverlay_dimensions(self):
+        ndoverlay = NdOverlay({
+            (0, 'A'): Curve([1, 2, 0]), (0, 'B'): Curve([1, 2, 1]),
+            (1, 'A'): Curve([1, 2, 2]), (1, 'B'): Curve([1, 2, 3])},
+                              ['num', 'cat']
+        ).opts({
+            'Curve': dict(
+                color=dim('num').categorize({0: 'red', 1: 'blue'}),
+                line_dash=dim('cat').categorize({'A': 'solid', 'B': 'dashed'})
+            )
+        })
+        plot = bokeh_renderer.get_plot(ndoverlay)
+        for (num, cat), sp in plot.subplots.items():
+            glyph = sp.handles['glyph']
+            color = glyph.line_color
+            if num == 0:
+                self.assertEqual(color, 'red')
+            else:
+                self.assertEqual(color, 'blue')
+            linestyle = glyph.line_dash
+            if cat == 'A':
+                self.assertEqual(linestyle, [])
+            else:
+                self.assertEqual(linestyle, [6])
+
+    def test_curve_style_mapping_constant_value_dimensions(self):
+        vdims = ['y', 'num', 'cat']
+        ndoverlay = NdOverlay({
+            0: Curve([(0, 1, 0, 'A'), (1, 0, 0, 'A')], vdims=vdims),
+            1: Curve([(0, 1, 0, 'B'), (1, 1, 0, 'B')], vdims=vdims),
+            2: Curve([(0, 1, 1, 'A'), (1, 2, 1, 'A')], vdims=vdims),
+            3: Curve([(0, 1, 1, 'B'), (1, 3, 1, 'B')], vdims=vdims)}
+        ).opts({
+            'Curve': dict(
+                color=dim('num').categorize({0: 'red', 1: 'blue'}),
+                line_dash=dim('cat').categorize({'A': 'solid', 'B': 'dashed'})
+            )
+        })
+        plot = bokeh_renderer.get_plot(ndoverlay)
+        for k, sp in plot.subplots.items():
+            glyph = sp.handles['glyph']
+            color = glyph.line_color
+            if ndoverlay[k].iloc[0, 2] == 0:
+                self.assertEqual(color, 'red')
+            else:
+                self.assertEqual(color, 'blue')
+            linestyle = glyph.line_dash
+            if ndoverlay[k].iloc[0, 3] == 'A':
+                self.assertEqual(linestyle, [])
+            else:
+                self.assertEqual(linestyle, [6])

holoviews/tests/plotting/matplotlib/testcurveplot.py

@@ -6,6 +6,7 @@
 from holoviews.core.overlay import NdOverlay
 from holoviews.core.util import pd
 from holoviews.element import Curve
+from holoviews.util.transform import dim
 
 from .testplot import TestMPLPlot, mpl_renderer
 
@@ -185,3 +186,55 @@ def test_curve_linewidth_op(self):
                        vdims=['y', 'linewidth']).options(linewidth='linewidth')
         with self.assertRaises(Exception):
             mpl_renderer.get_plot(curve)
+
+    def test_curve_style_mapping_ndoverlay_dimensions(self):
+        ndoverlay = NdOverlay({
+            (0, 'A'): Curve([1, 2, 0]), (0, 'B'): Curve([1, 2, 1]),
+            (1, 'A'): Curve([1, 2, 2]), (1, 'B'): Curve([1, 2, 3])},
+                              ['num', 'cat']
+        ).opts({
+            'Curve': dict(
+                color=dim('num').categorize({0: 'red', 1: 'blue'}),
+                linestyle=dim('cat').categorize({'A': '-.', 'B': '-'})
+            )
+        })
+        plot = mpl_renderer.get_plot(ndoverlay)
+        for (num, cat), sp in plot.subplots.items():
+            artist = sp.handles['artist']
+            color = artist.get_color()
+            if num == 0:
+                self.assertEqual(color, 'red')
+            else:
+                self.assertEqual(color, 'blue')
+            linestyle = artist.get_linestyle()
+            if cat == 'A':
+                self.assertEqual(linestyle, '-.')
+            else:
+                self.assertEqual(linestyle, '-')
+
+    def test_curve_style_mapping_constant_value_dimensions(self):
+        vdims = ['y', 'num', 'cat']
+        ndoverlay = NdOverlay({
+            0: Curve([(0, 1, 0, 'A'), (1, 0, 0, 'A')], vdims=vdims),
+            1: Curve([(0, 1, 0, 'B'), (1, 1, 0, 'B')], vdims=vdims),
+            2: Curve([(0, 1, 1, 'A'), (1, 2, 1, 'A')], vdims=vdims),
+            3: Curve([(0, 1, 1, 'B'), (1, 3, 1, 'B')], vdims=vdims)}
+        ).opts({
+            'Curve': dict(
+                color=dim('num').categorize({0: 'red', 1: 'blue'}),
+                linestyle=dim('cat').categorize({'A': '-.', 'B': '-'})
+            )
+        })
+        plot = mpl_renderer.get_plot(ndoverlay)
+        for k, sp in plot.subplots.items():
+            artist = sp.handles['artist']
+            color = artist.get_color()
+            if ndoverlay[k].iloc[0, 2] == 0:
+                self.assertEqual(color, 'red')
+            else:
+                self.assertEqual(color, 'blue')
+            linestyle = artist.get_linestyle()
+            if ndoverlay[k].iloc[0, 3] == 'A':
+                self.assertEqual(linestyle, '-.')
+            else:
+                self.assertEqual(linestyle, '-')