Fix layout titles (#3041)

holoviews/plotting/bokeh/plot.py

@@ -22,6 +22,7 @@
 
 from bokeh.layouts import gridplot
 from bokeh.plotting.helpers import _known_tools as known_tools
+from holoviews.plotting.bokeh.util import theme_attr_json
 
 TOOLS = {name: tool if isinstance(tool, basestring) else type(tool())
          for name, tool in known_tools.items()}
@@ -340,28 +341,52 @@ class CompositePlot(BokehPlot):
     to such a plot.
     """
 
-    fontsize = param.Parameter(default={'title': '16pt'}, allow_None=True,  doc="""
+    fontsize = param.Parameter(default={'title': '15pt'}, allow_None=True,  doc="""
        Specifies various fontsizes of the displayed text.
 
        Finer control is available by supplying a dictionary where any
        unmentioned keys reverts to the default sizes, e.g:
 
           {'title': '15pt'}""")
 
-    _title_template = "<span style='font-size: {fontsize}'><b>{title}</b></font>"
+    _title_template = (
+        '<span style='
+        '"color:{color};font-family:{font};'
+        'font-style:{fontstyle};font-weight:{fontstyle};'  # italic/bold
+        'font-size:{fontsize}">'
+        '{title}</span>'
+    )
 
     def _get_title(self, key):
         title_div = None
         title = self._format_title(key) if self.show_title else ''
-        if title:
-            fontsize = self._fontsize('title')
-            title_tags = self._title_template.format(title=title,
-                                                     **fontsize)
-            if 'title' in self.handles:
-                title_div = self.handles['title']
-            else:
-                title_div = Div()
-            title_div.text = title_tags
+        if not title:
+            return title_div
+
+        title_json = theme_attr_json(self.renderer.theme, 'Title')
+        color = title_json.get('text_color', None)
+        font = title_json.get('text_font', 'Arial')
+        fontstyle = title_json.get('text_font_style', 'bold')
+        fontsize = self._fontsize('title')['fontsize']
+        if fontsize == '15pt':  # if default
+            fontsize = title_json.get('text_font_size', '15pt')
+            if 'em' in fontsize:
+                # it's smaller than it shosuld be so add 0.25
+                fontsize = str(float(fontsize[:-2]) + 0.25) + 'em'
+
+        title_tags = self._title_template.format(
+            color=color,
+            font=font,
+            fontstyle=fontstyle,
+            fontsize=fontsize,
+            title=title)
+
+        if 'title' in self.handles:
+            title_div = self.handles['title']
+        else:
+            title_div = Div(width=450)  # so it won't wrap long titles easily
+        title_div.text = title_tags
+
         return title_div
 
     @property

holoviews/plotting/bokeh/util.py

@@ -23,6 +23,11 @@
 from bokeh.models import Model, ToolbarBox, FactorRange, Range1d, Plot, Spacer, CustomJS
 from bokeh.models.widgets import DataTable, Tabs, Div
 from bokeh.plotting import Figure
+from bokeh.themes.theme import Theme
+if bokeh_version <= '0.13.0':
+    built_in_themes = {}
+else:
+    from bokeh.themes import built_in_themes
 
 try:
     from bkcharts import Chart
@@ -660,3 +665,12 @@ def colormesh(X, Y):
     X = np.column_stack([X1, X2, X3, X4, X1])
     Y = np.column_stack([Y1, Y2, Y3, Y4, Y1])
     return X, Y
+
+
+def theme_attr_json(theme, attr):
+    if isinstance(theme, str) and theme in built_in_themes:
+        return built_in_themes[theme]._json['attrs'].get(attr, {})
+    elif isinstance(theme, Theme):
+        return theme._json['attrs'].get(attr, {})
+    else:
+        return {}

holoviews/tests/plotting/bokeh/testgridplot.py

@@ -23,7 +23,8 @@ def test_grid_title(self):
         plot = bokeh_renderer.get_plot(grid)
         title = plot.handles['title']
         self.assertIsInstance(title, Div)
-        text = "<span style='font-size: 16pt'><b>X: 0</b></font>"
+        text = ('<span style="color:black;font-family:Arial;'
+                'font-style:bold;font-weight:bold;font-size:16pt">X: 0</span>')
         self.assertEqual(title.text, text)
 
     def test_grid_title_update(self):
@@ -34,7 +35,8 @@ def test_grid_title_update(self):
         plot.update(1)
         title = plot.handles['title']
         self.assertIsInstance(title, Div)
-        text = "<span style='font-size: 16pt'><b>X: 1</b></font>"
+        text = ('<span style="color:black;font-family:Arial;'
+                'font-style:bold;font-weight:bold;font-size:16pt">X: 1</span>')
         self.assertEqual(title.text, text)
 
     def test_gridmatrix_overlaid_batched(self):

holoviews/tests/plotting/bokeh/testlayoutplot.py

@@ -34,7 +34,8 @@ def test_layout_title(self):
         plot = bokeh_renderer.get_plot(hmap1+hmap2)
         title = plot.handles['title']
         self.assertIsInstance(title, Div)
-        text = "<span style='font-size: 16pt'><b>Default: 0</b></font>"
+        text = ('<span style="color:black;font-family:Arial;font-style:bold;'
+                'font-weight:bold;font-size:12pt">Default: 0</span>')
         self.assertEqual(title.text, text)
 
     def test_layout_title_fontsize(self):
@@ -44,7 +45,8 @@ def test_layout_title_fontsize(self):
         plot = bokeh_renderer.get_plot(layout)
         title = plot.handles['title']
         self.assertIsInstance(title, Div)
-        text = "<span style='font-size: 12pt'><b>Default: 0</b></font>"
+        text = ('<span style="color:black;font-family:Arial;font-style:bold;'
+                'font-weight:bold;font-size:12pt">Default: 0</span>')
         self.assertEqual(title.text, text)
 
     def test_layout_title_show_title_false(self):
@@ -61,7 +63,8 @@ def test_layout_title_update(self):
         plot.update(1)
         title = plot.handles['title']
         self.assertIsInstance(title, Div)
-        text = "<span style='font-size: 16pt'><b>Default: 1</b></font>"
+        text = ('<span style="color:black;font-family:Arial;font-style:bold;'
+                'font-weight:bold;font-size:12pt">Default: 1</span>')
         self.assertEqual(title.text, text)
 
     def test_layout_gridspaces(self):
@@ -164,7 +167,7 @@ def test_layout_plot_tabs_with_adjoints(self):
         self.assertIsInstance(panel2, Panel)
         self.assertEqual(panel1.title, 'Curve I')
         self.assertEqual(panel2.title, 'AdjointLayout I')
-        
+
     def test_layout_shared_source_synced_update(self):
         hmap = HoloMap({i: Dataset({chr(65+j): np.random.rand(i+2)
                                     for j in range(4)}, kdims=['A', 'B', 'C', 'D'])