Add a zoom tool per subcoordinate_y group (#6122)

holoviews/plotting/bokeh/element.py

@@ -1,4 +1,5 @@
 import warnings
+from collections import defaultdict
 from itertools import chain
 from types import FunctionType
 
@@ -3025,9 +3026,77 @@ def _merge_tools(self, subplot):
                 subplot.handles['zooms_subcoordy'].values(),
                 self.handles['zooms_subcoordy'].values(),
             ):
-                renderers = list(util.unique_iterator(subplot_zoom.renderers + overlay_zoom.renderers))
+                renderers = list(util.unique_iterator(overlay_zoom.renderers + subplot_zoom.renderers))
                 overlay_zoom.renderers = renderers
 
+    def _postprocess_subcoordinate_y_groups(self, overlay, plot):
+        """
+        Add a zoom tool per group to the overlay.
+        """
+        # First, just process and validate the groups and their content.
+        groups = defaultdict(list)
+
+        # If there are groups AND there are subcoordinate_y elements without a group.
+        if any(el.group != type(el).__name__ for el in overlay) and any(
+            el.opts.get('plot').kwargs.get('subcoordinate_y', False)
+            and el.group == type(el).__name__
+            for el in overlay
+        ):
+            raise ValueError(
+                'The subcoordinate_y overlay contains elements with a defined group, each '
+                'subcoordinate_y element in the overlay must have a defined group.'
+            )
+
+        for el in overlay:
+            # group is the Element type per default (e.g. Curve, Spike).
+            if el.group == type(el).__name__:
+                continue
+            if not el.opts.get('plot').kwargs.get('subcoordinate_y', False):
+                raise ValueError(
+                    f"All elements in group {el.group!r} must set the option "
+                    f"'subcoordinate_y=True'. Not found for: {el}"
+                )
+            groups[el.group].append(el)
+
+        # No need to go any further if there's just one group.
+        if len(groups) <= 1:
+            return
+
+        # At this stage, there's only one zoom tool (e.g. 1 wheel_zoom) that
+        # has all the renderers (e.g. all the curves in the overlay).
+        # We want to create as many zoom tools as groups, for each group
+        # the zoom tool must have the renderers of the elements of the group.
+        zoom_tools = self.handles['zooms_subcoordy']
+        for zoom_tool_name, zoom_tool in zoom_tools.items():
+            renderers_per_group = defaultdict(list)
+            # We loop through each overlay sub-elements and empty the list of
+            # renderers of the initial tool.
+            for el in overlay:
+                if el.group not in groups:
+                    continue
+                renderers_per_group[el.group].append(zoom_tool.renderers.pop(0))
+
+            if zoom_tool.renderers:
+                raise RuntimeError(f'Found unexpected zoom renderers {zoom_tool.renderers}')
+
+            new_ztools = []
+            # Create a new tool per group with the right renderers and a custom description.
+            for grp, grp_renderers in renderers_per_group.items():
+                new_tool = zoom_tool.clone()
+                new_tool.renderers = grp_renderers
+                new_tool.description = f"{zoom_tool_name.replace('_', ' ').title()} ({grp})"
+                new_ztools.append(new_tool)
+            # Revert tool order so the upper tool in the toolbar corresponds to the
+            # upper group in the overlay.
+            new_ztools = new_ztools[::-1]
+
+            # Update the handle for good measure.
+            zoom_tools[zoom_tool_name] = new_ztools
+
+            # Replace the original tool by the new ones
+            idx = plot.tools.index(zoom_tool)
+            plot.tools[idx:idx+1] = new_ztools
+
     def _get_dimension_factors(self, overlay, ranges, dimension):
         factors = []
         for k, sp in self.subplots.items():
@@ -3132,6 +3201,9 @@ def initialize_plot(self, ranges=None, plot=None, plots=None):
                     reordered.append(reversed_renderers.pop(0))
             plot.renderers = reordered
 
+        if self.subcoordinate_y:
+            self._postprocess_subcoordinate_y_groups(element, plot)
+
         if self.tabs:
             self.handles['plot'] = Tabs(
                 tabs=panels, width=self.width, height=self.height,

holoviews/tests/plotting/bokeh/test_subcoordy.py

@@ -261,3 +261,133 @@ def test_tools_instance_zoom_untouched(self):
                     break
             else:
                 raise AssertionError('Provided zoom not found.')
+
+    def test_single_group(self):
+        # Same as test_bool_base, to check nothing is affected by defining
+        # a single group.
+
+        overlay = Overlay([Curve(range(10), label=f'Data {i}', group='Group').opts(subcoordinate_y=True) for i in range(2)])
+        plot = bokeh_renderer.get_plot(overlay)
+        # subcoordinate_y is propagated to the overlay
+        assert plot.subcoordinate_y is True
+        # the figure has only one yaxis
+        assert len(plot.state.yaxis) == 1
+        # the overlay has two subplots
+        assert len(plot.subplots) == 2
+        assert ('Group', 'Data_0') in plot.subplots
+        assert ('Group', 'Data_1') in plot.subplots
+        # the range per subplots are correctly computed
+        sp1 = plot.subplots[('Group', 'Data_0')]
+        assert sp1.handles['glyph_renderer'].coordinates.y_target.start == -0.5
+        assert sp1.handles['glyph_renderer'].coordinates.y_target.end == 0.5
+        sp2 = plot.subplots[('Group', 'Data_1')]
+        assert sp2.handles['glyph_renderer'].coordinates.y_target.start == 0.5
+        assert sp2.handles['glyph_renderer'].coordinates.y_target.end == 1.5
+        # y_range is correctly computed
+        assert plot.handles['y_range'].start == -0.5
+        assert plot.handles['y_range'].end == 1.5
+        # extra_y_range is empty
+        assert plot.handles['extra_y_ranges'] == {}
+        # the ticks show the labels
+        assert plot.state.yaxis.ticker.ticks == [0, 1]
+        assert plot.state.yaxis.major_label_overrides == {0: 'Data 0', 1: 'Data 1'}
+
+    def test_multiple_groups(self):
+        overlay = Overlay([
+            Curve(range(10), label=f'{group} / {i}', group=group).opts(subcoordinate_y=True)
+            for group in ['A', 'B']
+            for i in range(2)
+        ])
+        plot = bokeh_renderer.get_plot(overlay)
+        # subcoordinate_y is propagated to the overlay
+        assert plot.subcoordinate_y is True
+        # the figure has only one yaxis
+        assert len(plot.state.yaxis) == 1
+        # the overlay has two subplots
+        assert len(plot.subplots) == 4
+        assert ('A', 'A_over_0') in plot.subplots
+        assert ('A', 'A_over_1') in plot.subplots
+        assert ('B', 'B_over_0') in plot.subplots
+        assert ('B', 'B_over_1') in plot.subplots
+        # the range per subplots are correctly computed
+        sp1 = plot.subplots[('A', 'A_over_0')]
+        assert sp1.handles['glyph_renderer'].coordinates.y_target.start == -0.5
+        assert sp1.handles['glyph_renderer'].coordinates.y_target.end == 0.5
+        sp2 = plot.subplots[('A', 'A_over_1')]
+        assert sp2.handles['glyph_renderer'].coordinates.y_target.start == 0.5
+        assert sp2.handles['glyph_renderer'].coordinates.y_target.end == 1.5
+        sp3 = plot.subplots[('B', 'B_over_0')]
+        assert sp3.handles['glyph_renderer'].coordinates.y_target.start == 1.5
+        assert sp3.handles['glyph_renderer'].coordinates.y_target.end == 2.5
+        sp4 = plot.subplots[('B', 'B_over_1')]
+        assert sp4.handles['glyph_renderer'].coordinates.y_target.start == 2.5
+        assert sp4.handles['glyph_renderer'].coordinates.y_target.end == 3.5
+        # y_range is correctly computed
+        assert plot.handles['y_range'].start == -0.5
+        assert plot.handles['y_range'].end == 3.5
+        # extra_y_range is empty
+        assert plot.handles['extra_y_ranges'] == {}
+        # the ticks show the labels
+        assert plot.state.yaxis.ticker.ticks == [0, 1, 2, 3]
+        assert plot.state.yaxis.major_label_overrides == {
+            0: 'A / 0', 1: 'A / 1',
+            2: 'B / 0', 3: 'B / 1',
+        }
+
+    def test_multiple_groups_wheel_zoom_configured(self):
+        # Same as test_tools_default_wheel_zoom_configured
+
+        groups = ['A', 'B']
+        overlay = Overlay([
+            Curve(range(10), label=f'{group} / {i}', group=group).opts(subcoordinate_y=True)
+            for group in groups
+            for i in range(2)
+        ])
+        plot = bokeh_renderer.get_plot(overlay)
+        zoom_tools = [tool for tool in plot.state.tools if isinstance(tool, WheelZoomTool)]
+        assert zoom_tools == plot.handles['zooms_subcoordy']['wheel_zoom']
+        assert len(zoom_tools) == len(groups)
+        for zoom_tool, group in zip(zoom_tools, reversed(groups)):
+            assert len(zoom_tool.renderers) == 2
+            assert len(set(zoom_tool.renderers)) == 2
+            assert zoom_tool.dimensions == 'height'
+            assert zoom_tool.level == 1
+            assert zoom_tool.description == f'Wheel Zoom ({group})'
+
+    def test_single_group_overlaid_no_error(self):
+        overlay = Overlay([Curve(range(10), label=f'Data {i}', group='Group').opts(subcoordinate_y=True) for i in range(2)])
+        with_span = VSpan(1, 2) * overlay * VSpan(3, 4)
+        bokeh_renderer.get_plot(with_span)
+
+    def test_multiple_groups_overlaid_no_error(self):
+        overlay = Overlay([
+            Curve(range(10), label=f'{group} / {i}', group=group).opts(subcoordinate_y=True)
+            for group in ['A', 'B']
+            for i in range(2)
+        ])
+        with_span = VSpan(1, 2) * overlay * VSpan(3, 4)
+        bokeh_renderer.get_plot(with_span)
+
+    def test_missing_group_error(self):
+        curves = []
+        for i, group in enumerate(['A', 'B', 'C']):
+            for i in range(2):
+                label = f'{group}{i}'
+                if group == "B":
+                    curve = Curve(range(10), label=label, group=group).opts(
+                        subcoordinate_y=True
+                    )
+                else:
+                    curve = Curve(range(10), label=label).opts(
+                        subcoordinate_y=True
+                    )
+                curves.append(curve)
+
+        with pytest.raises(
+            ValueError,
+            match=(
+                'The subcoordinate_y overlay contains elements with a defined group, each '
+                'subcoordinate_y element in the overlay must have a defined group.'
+            )
+        ):
+            bokeh_renderer.get_plot(Overlay(curves))