title: export svgs in bokeh for vbar_stack with hatch patterns
body: <p>I wanted to export svg and it is executing but it gives no output after waiting a long time. Can you please help me out?</p>
  <p>I wanted to have hatched vbar stack as output as svg. I have found it takes that much time for exporting svg.
  Links: <a href="https://github.com/bokeh/bokeh/issues/8192" rel="nofollow noreferrer">https://github.com/bokeh/bokeh/issues/8192</a>
  Now I'm a bit confused whether it won't work for vbar plot or not?</p>
  <pre><code>from bokeh.plotting import figure, output_file, show
  from bokeh.models import Title
  from bokeh.core.properties import value
  from bokeh.layouts import row
  from bokeh.models import Legend
  from bokeh.io import export_svgs
  
  output_file('stacked.html')
  
  capacity = ['CO2_Cap', 'Min_RES_Quota', 'CO2_Tax', 'FIT']
  types = ['Lignite', 'Coal', 'CCGT', 'OCGT','Wind Onshore', 'Wind Offshore', 'Solar']
  colors = [&quot;#9a7b5c&quot;, &quot;#414141&quot;, &quot;#c7dada&quot;, &quot;#c7dada&quot;, &quot;#5a67ff&quot;,'#00b8f2', '#fff340']
  
  maxload = [90.03467675, 90.03467675, 90.03467675, 90.03467675]
  Total_demand = [540.7686148, 540.7686148, 540.7686148, 540.7686148]
  
  
  data = {'capacity' : capacity,
          'Lignite'   : [0,22.28330605,0,25.76575924],
          'Coal'   : [0, 0, 0,0],
          'CCGT'   : [52.12309276, 0.209356135, 52.12598273, 6.416971663],
          'OCGT'   : [10.1753325,20.35167058,10.1729694,22.18142626],
          'Wind Onshore': [90.66714923, 77.28982927, 90.6875821, 86.3713515],
          'Wind Offshore': [24.26075426, 53.92876756, 24.25201174, 60.265434],
          'Solar' : [90.1174063, 159.3567357, 90.0774928, 178.0811123]
          }
  
  s1 = figure(x_range=capacity, plot_height=450,plot_width=655)
  
  
  s1.vbar_stack(types, x='capacity', width=0.3, color=colors, source=data,
               legend=[value(x) for x in types], hatch_pattern=['dot', 'spiral', 'vertical_wave', 'right_diagonal_line', 'vertical_dash', 'left_diagonal_line', 'ring'])
  s1.line(x = capacity, y = maxload, color=&quot;red&quot;, line_width=3, legend_label = &quot;max_load&quot;)
  
  s1.legend.location = &quot;bottom_right&quot;
  s1.legend.click_policy=&quot;hide&quot;
  #s1.add_layout(Title(text=&quot;Total CO2 Emissions (in 10^6t) &quot;, align=&quot;center&quot;), &quot;left&quot;)
  
  
  show(s1)
  
  
  from bokeh.io import export_svgs
  s1.output_backend = &quot;svg&quot;
  export_svgs(s1, filename=&quot;plot11111.svg&quot;)
  </code></pre>