From 3251c83fe8da61e53fdcaf9ab653304b4d557834 Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <philippjfr@continuum.io>
Date: Tue, 13 Jun 2017 13:36:00 +0100
Subject: [PATCH] Bokeh SplinePlot handles multiple cubic splines (#1529)

* Bokeh SplinePlot handles multiple cubic splines correctly

* Matplotlib SplinePlot handles empty Spline

* Simplified bokeh SplinePlot implementation
---
 holoviews/plotting/bokeh/annotation.py | 26 ++++++++++++++++----------
 holoviews/plotting/mpl/annotation.py   |  2 ++
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/holoviews/plotting/bokeh/annotation.py b/holoviews/plotting/bokeh/annotation.py
index a17821f2c5..7d3646eac6 100644
--- a/holoviews/plotting/bokeh/annotation.py
+++ b/holoviews/plotting/bokeh/annotation.py
@@ -87,14 +87,20 @@ class SplinePlot(ElementPlot):
     _plot_methods = dict(single='bezier')
 
     def get_data(self, element, ranges=None, empty=False):
-        data_attrs = ['x0', 'y0', 'x1', 'y1',
-                      'cx0', 'cx1', 'cy0', 'cy1']
-        if empty:
-            data = {attr: [] for attr in data_attrs}
-        else:
-            verts = np.array(element.data[0])
-            xs, ys = verts[:, 0], verts[:, 1]
-            data = dict(x0=[xs[0]], y0=[ys[0]], x1=[xs[-1]], y1=[ys[-1]],
-                        cx0=[xs[1]], cy0=[ys[1]], cx1=[xs[2]], cy1=[ys[2]])
-
+        data_attrs = ['x0', 'y0', 'cx0', 'cy0', 'cx1', 'cy1', 'x1', 'y1',]
+        verts = np.array(element.data[0])
+        inds = np.where(np.array(element.data[1])==1)[0]
+        data = {da: [] for da in data_attrs}
+        skipped = False
+        for vs in np.split(verts, inds[1:]):
+            if len(vs) != 4:
+                skipped = len(vs) > 1
+                continue
+            for x, y, xl, yl in zip(vs[:, 0], vs[:, 1], data_attrs[::2], data_attrs[1::2]):
+                data[xl].append(x)
+                data[yl].append(y)
+        if skipped:
+            self.warning('Bokeh SplitPlot only support cubic splines, '
+                         'unsupported splines were skipped during plotting.')
+        data = {da: data[da] for da in data_attrs}
         return (data, dict(zip(data_attrs, data_attrs)))
diff --git a/holoviews/plotting/mpl/annotation.py b/holoviews/plotting/mpl/annotation.py
index 684a1be5c1..b169ca59f6 100644
--- a/holoviews/plotting/mpl/annotation.py
+++ b/holoviews/plotting/mpl/annotation.py
@@ -106,6 +106,8 @@ class SplinePlot(AnnotationPlot):
 
     def draw_annotation(self, axis, data, opts):
         verts, codes = data
+        if not len(verts):
+            return []
         patch = patches.PathPatch(matplotlib.path.Path(verts, codes),
                                   facecolor='none', **opts)
         axis.add_patch(patch)