Allow defining CompositeElementPlot glyph order (#2169)

holoviews/plotting/bokeh/element.py

@@ -26,7 +26,7 @@
 from ..util import dynamic_update, process_cmap
 from .plot import BokehPlot, TOOLS
 from .util import (mpl_to_bokeh, get_tab_title,  py2js_tickformatter,
-                   rgba_tuple, recursive_model_update)
+                   rgba_tuple, recursive_model_update, glyph_order)
 
 property_prefixes = ['selection', 'nonselection', 'muted', 'hover']
 
@@ -936,10 +936,12 @@ def _init_glyphs(self, plot, element, ranges, source, data=None, mapping=None, s
             style = self.style[self.cyclic_index]
             data, mapping, style = self.get_data(element, ranges, style)
 
+        keys = glyph_order(dict(data, **mapping), self._draw_order)
+
         source_cache = {}
         current_id = element._plot_id
         self.handles['previous_id'] = current_id
-        for key in dict(mapping, **data):
+        for key in keys:
             ds_data = data.get(key, {})
             if id(ds_data) in source_cache:
                 source = source_cache[id(ds_data)]
@@ -993,13 +995,8 @@ def _update_glyphs(self, element, ranges):
         style = self.style[self.cyclic_index]
         data, mapping, style = self.get_data(element, ranges, style)
 
-        # Order glyphs by supplied draw order
-        keys = sorted(dict(mapping, **data))
-        def order_fn(glyph):
-            matches = [item for item in self._draw_order if glyph.startswith(item)]
-            if matches: return self._draw_order.index(matches[0])
-            return 1e6+keys.index(glyph)
-        for key in sorted(keys, key=order_fn):
+        keys = glyph_order(dict(data, **mapping), self._draw_order)
+        for key in keys:
             gdata = data.get(key)
             source = self.handles[key+'_source']
             glyph = self.handles.get(key+'_glyph')

holoviews/plotting/bokeh/util.py

@@ -602,3 +602,23 @@ def date_to_integer(date):
     else:
         raise ValueError('Datetime type not recognized')
     return dt_int
+
+
+def glyph_order(keys, draw_order=[]):
+    """
+    Orders a set of glyph handles using regular sort and an explicit
+    sort order. The explicit draw order must take the form of a list
+    of glyph names while the keys should be glyph names with a custom
+    suffix. The draw order may only match subset of the keys and any
+    matched items will take precedence over other entries.
+
+    >>> glyph_order(['scatter_1', 'patch_1', 'rect_1'], \
+                    ['scatter', 'patch'])
+    ['scatter_1', 'patch_1', 'rect_1']
+    """
+    keys = sorted(keys)
+    def order_fn(glyph):
+        matches = [item for item in draw_order if glyph.startswith(item)]
+        return ((draw_order.index(matches[0]), glyph) if matches else
+                (1e9+keys.index(glyph), glyph))
+    return sorted(keys, key=order_fn)