bar plot multi_level=False issues with Bokeh backend in Safari

[michi42]

Setting multi_level=False for a bar plot sets major_label_text_font_size = 0pt (see https://github.com/holoviz/holoviews/blob/main/holoviews/plotting/bokeh/chart.py#L802). This does not work well in Safari which simply ignores "too small" fonts, leading to displayed, overlapping labels (see screenshot below).

As an alternative one could set major_label_text_alpha to 0, major_label_text_line_height to 0 and major_label_text_font_size to 1px to hide the labels:

props['major_label_text_font_size'] = '1px'
props['major_label_text_alpha'] = 0
props['major_label_text_line_height'] = 0

Possibly there could also be a nicer solution, avoiding these hacks to hide the labels altogether, using major_label_overrides or a custom ticker?

[hoxbro]

Can you share a minimal, reproducible example (MRE)?

I would like to fiddle around with the settings myself.

[michi42]

Apologies for the delay...

This triggers the problem for me with holoviews==1.14.9, bokeh==2.4.2, hvplot==0.8.0.

import pandas as pd
import holoviews as hv
import hvplot.pandas
hv.extension('bokeh')
pdf = pd.DataFrame({"ATLAS":{"Mar":1.0,"Apr":2.0},"CMS":{"Mar":3.0,"Apr":4.0}})
plt = pdf.hvplot(kind='bar', responsive=True, height=430).opts(multi_level=False)
hv.save(plt, 'sample.html', backend='bokeh')

Depending on the Safari version, it either renders with the second-level labels not hidden as expected (recent safari versions) or even breaks completely rendering with "invalid bbox" (older versions):

Adding the following hook works around the issue for all Safari versions I tested:

def hv_single_level_barplot_workaround(plot, element):
    xaxis = plot.handles['xaxis']
    if (not plot.multi_level) and xaxis.major_label_text_font_size == '0pt':
        xaxis.major_label_text_font_size = '1px'  # safari does not like 0pt
        xaxis.major_label_text_alpha = 0
        xaxis.major_label_text_line_height = 0

[hoxbro]

This looks fine for me running Holoviews=1.16:

Bokeh 2.4.3

Bokeh 3.1.1

[philippjfr]

Looks broken in 3.1.1 looking at your screenshot above.

[philippjfr]

See also #5726

[hoxbro]

I was mainly talking about the missing font, but yes, the bar is broken in 3.1.1.

[michi42]

Also in 2.4.3 the output is not correct in Safari, although it's not that obvious: multi_level=False should suppress the second-level category axis ("ATLAS" / "CMS" in my example). This is actually what is shown in the screenshot in the first post.

The expected output would be this:

[hoxbro]

I finally understood the problem... I have opened a PR with your suggested fix. Thank you for your patience. 👍