Add ArrowPlot implementation for bokeh (#1608)

* Small fix for CompositeElementPlot

* Added bokeh ArrowPlot

holoviews/plotting/bokeh/__init__.py

@@ -7,7 +7,7 @@
                      GridSpace, GridMatrix, NdLayout, config)
 from ...element import (Curve, Points, Scatter, Image, Raster, Path,
                         RGB, Histogram, Spread, HeatMap, Contours, Bars,
-                        Box, Bounds, Ellipse, Polygons, BoxWhisker,
+                        Box, Bounds, Ellipse, Polygons, BoxWhisker, Arrow,
                         ErrorBars, Text, HLine, VLine, Spline, Spikes,
                         Table, ItemTable, Area, HSV, QuadMesh, VectorField)
 from ...core.options import Options, Cycle, Palette
@@ -17,7 +17,7 @@
 except:
     DFrame = None
 
-from .annotation import TextPlot, LineAnnotationPlot, SplinePlot
+from .annotation import TextPlot, LineAnnotationPlot, SplinePlot, ArrowPlot
 from .callbacks import Callback # noqa (API import)
 from .element import OverlayPlot, ElementPlot
 from .chart import (PointPlot, CurvePlot, SpreadPlot, ErrorPlot, HistogramPlot,
@@ -79,6 +79,7 @@
                 VLine: LineAnnotationPlot,
                 Text: TextPlot,
                 Spline: SplinePlot,
+                Arrow: ArrowPlot,
 
                 # Tabular
                 Table: TablePlot,
@@ -150,6 +151,7 @@ def colormap_generator(palette):
 # Annotations
 options.HLine = Options('style', color=Cycle(), line_width=3, alpha=1)
 options.VLine = Options('style', color=Cycle(), line_width=3, alpha=1)
+options.Arrow = Options('style', arrow_size=10)
 
 # Define composite defaults
 options.GridMatrix = Options('plot', shared_xaxis=True, shared_yaxis=True,

holoviews/plotting/bokeh/annotation.py

@@ -1,10 +1,18 @@
 from collections import defaultdict
 
 import numpy as np
-from bokeh.models import Span
+from bokeh.models import Span, Arrow
+try:
+    from bokeh.models.arrow_heads import TeeHead, NormalHead
+    arrow_start = {'<->': NormalHead, '<|-|>': NormalHead}
+    arrow_end = {'->': NormalHead, '-[': TeeHead, '-|>': NormalHead, '-': None}
+except:
+    from bokeh.models.arrow_heads import OpenHead, NormalHead
+    arrow_start = {'<->': NormalHead, '<|-|>': NormalHead}
+    arrow_end = {'->': NormalHead, '-[': OpenHead, '-|>': NormalHead, '-': None}
 
 from ...element import HLine
-from .element import ElementPlot, text_properties, line_properties
+from .element import ElementPlot, CompositeElementPlot, text_properties, line_properties
 
 
 class TextPlot(ElementPlot):
@@ -104,3 +112,75 @@ def get_data(self, element, ranges=None, empty=False):
                          'unsupported splines were skipped during plotting.')
         data = {da: data[da] for da in data_attrs}
         return (data, dict(zip(data_attrs, data_attrs)))
+
+
+
+class ArrowPlot(CompositeElementPlot):
+
+    style_opts = (['arrow_%s' % p for p in line_properties+['size']] + text_properties)
+
+    _style_groups = {'arrow': 'arrow', 'label': 'text'}
+
+    _update_handles = ['glyph']
+
+    _plot_methods = dict(single='text')
+
+    def get_data(self, element, ranges=None, empty=False):
+        plot = self.state
+        label_mapping = dict(x='x', y='y', text='text')
+
+        # Compute arrow
+        x1, y1 = element.x, element.y
+        axrange = plot.x_range if self.invert_axes else plot.y_range
+        span = (axrange.end - axrange.start) / 6.
+        if element.direction == '^':
+            x2, y2 = x1, y1-span
+            label_mapping['text_baseline'] = 'top'
+        elif element.direction == '<':
+            x2, y2 = x1+span, y1
+            label_mapping['text_align'] = 'left'
+            label_mapping['text_baseline'] = 'middle'
+        elif element.direction == '>':
+            x2, y2 = x1-span, y1
+            label_mapping['text_align'] = 'right'
+            label_mapping['text_baseline'] = 'middle'
+        else:
+            x2, y2 = x1, y1+span
+            label_mapping['text_baseline'] = 'bottom'
+        arrow_opts = {'x_end': x1, 'y_end': y1,
+                      'x_start': x2, 'y_start': y2}
+
+        # Define arrowhead
+        arrow_opts['arrow_start'] = arrow_start.get(element.arrowstyle, None)
+        arrow_opts['arrow_end'] = arrow_end.get(element.arrowstyle, NormalHead)
+
+        # Compute label
+        if self.invert_axes:
+            label_data = dict(x=[y2], y=[x2])
+        else:
+            label_data = dict(x=[x2], y=[y2])
+        label_data['text'] = [element.text]
+        return ({'label': label_data},
+                {'arrow': arrow_opts, 'label': label_mapping})
+
+    def _init_glyph(self, plot, mapping, properties, key):
+        """
+        Returns a Bokeh glyph object.
+        """
+        properties.pop('legend')
+        if key == 'arrow':
+            properties.pop('source')
+            arrow_end = mapping.pop('arrow_end')
+            arrow_start = mapping.pop('arrow_start')
+            start = arrow_start(**properties) if arrow_start else None
+            end = arrow_end(**properties) if arrow_end else None
+            glyph = Arrow(start=start, end=end, **dict(**mapping))
+        else:
+            properties = {p if p == 'source' else 'text_'+p: v
+                          for p, v in properties.items()}
+            glyph, _ = super(ArrowPlot, self)._init_glyph(plot, mapping, properties, 'text')
+        plot.renderers.append(glyph)
+        return None, glyph
+
+    def get_extents(self, element, ranges=None):
+        return None, None, None, None

holoviews/plotting/bokeh/element.py

@@ -225,6 +225,7 @@ def _hover_opts(self, element):
         dims += element.dimensions()
         return list(util.unique_iterator(dims)), {}
 
+
     def _init_tools(self, element, callbacks=[]):
         """
         Processes the list of tools to be supplied to the plot.
@@ -960,13 +961,13 @@ def _init_glyphs(self, plot, element, ranges, source):
             current_id = element._plot_id
 
         self.handles['previous_id'] = current_id
-        for key, gdata in data.items():
-            source = self._init_datasource(gdata)
+        for key in dict(mapping, **data):
+            source = self._init_datasource(data.get(key, {}))
             self.handles[key+'_source'] = source
             properties = self._glyph_properties(plot, element, source, ranges)
             properties = self._process_properties(key, properties)
             with abbreviated_exception():
-                renderer, glyph = self._init_glyph(plot, mapping[key], properties, key)
+                renderer, glyph = self._init_glyph(plot, mapping.get(key, {}), properties, key)
             self.handles[key+'_glyph'] = glyph
             if isinstance(renderer, Renderer):
                 self.handles[key+'glyph_renderer'] = renderer
@@ -975,7 +976,7 @@ def _init_glyphs(self, plot, element, ranges, source):
 
             # Update plot, source and glyph
             with abbreviated_exception():
-                self._update_glyph(renderer, properties, mapping[key], glyph)
+                self._update_glyph(renderer, properties, mapping.get(key, {}), glyph)
 
 
     def _process_properties(self, key, properties):