subcoordinate_y: reverse the renderers by default (#6194)

holoviews/plotting/bokeh/element.py

@@ -2201,7 +2201,6 @@ def _init_glyph(self, plot, mapping, properties, key):
         return renderer, renderer.glyph
 
 
-
 class ColorbarPlot(ElementPlot):
     """
     ColorbarPlot provides methods to create colormappers and colorbar
@@ -2617,7 +2616,6 @@ def _process_legend(self, plot=None):
                         r.muted = self.legend_muted
 
 
-
 class AnnotationPlot:
     """
     Mix-in plotting subclass for AnnotationPlots which do not have a legend.
@@ -2782,7 +2780,6 @@ def _process_legend(self, overlay):
                 for r in item.renderers:
                     r.muted = self.legend_muted or r.muted
 
-
     def _init_tools(self, element, callbacks=None):
         """
         Processes the list of tools to be supplied to the plot.
@@ -2825,7 +2822,6 @@ def _init_tools(self, element, callbacks=None):
         self.handles['hover_tools'] = hover_tools
         return init_tools
 
-
     def _merge_tools(self, subplot):
         """
         Merges tools on the overlay with those on the subplots.
@@ -2923,6 +2919,7 @@ def initialize_plot(self, ranges=None, plot=None, plots=None):
             self._update_ranges(element, ranges)
 
         panels = []
+        subcoord_y_glyph_renderers = []
         for key, subplot in self.subplots.items():
             frame = None
             if self.tabs:
@@ -2941,6 +2938,21 @@ def initialize_plot(self, ranges=None, plot=None, plots=None):
                     title = get_tab_title(key, frame, self.hmap.last)
                 panels.append(TabPanel(child=child, title=title))
             self._merge_tools(subplot)
+            if getattr(subplot, "subcoordinate_y", False) and (
+                glyph_renderer := subplot.handles.get("glyph_renderer")
+            ):
+                subcoord_y_glyph_renderers.append(glyph_renderer)
+
+        if self.subcoordinate_y:
+            # Reverse the subcoord-y renderers only.
+            reversed_renderers = subcoord_y_glyph_renderers[::-1]
+            reordered = []
+            for item in plot.renderers:
+                if item not in subcoord_y_glyph_renderers:
+                    reordered.append(item)
+                else:
+                    reordered.append(reversed_renderers.pop(0))
+            plot.renderers = reordered
 
         if self.tabs:
             self.handles['plot'] = Tabs(

holoviews/tests/plotting/bokeh/test_subcoordy.py

@@ -40,6 +40,17 @@ def test_bool_base(self):
         assert plot.state.yaxis.ticker.ticks == [0, 1]
         assert plot.state.yaxis.major_label_overrides == {0: 'Data 0', 1: 'Data 1'}
 
+    def test_renderers_reversed(self):
+        overlay = Overlay([Curve(range(10), label=f'Data {i}').opts(subcoordinate_y=True) for i in range(2)])
+        overlay = VSpan(0, 1, label='back') * overlay * VSpan(2, 3, label='front')
+        plot = bokeh_renderer.get_plot(overlay)
+        renderers = plot.handles['plot'].renderers
+        assert (renderers[0].left, renderers[0].right) == (0, 1)
+        # Only the subcoord-y renderers are reversed by default.
+        assert renderers[1].name == 'Data 1'
+        assert renderers[2].name == 'Data 0'
+        assert (renderers[3].left, renderers[3].right) == (2, 3)
+
     def test_bool_scale(self):
         test_data = [
             (0.5, (-0.25, 0.25), (0.75, 1.25), (-0.25, 1.25)),