Support CSS functions & variables for size definitions

[chanchalsen]

The code throws error with cannot convert to float in this statement:

return max(MIN_FONT_SIZE, relative * float(value)) 

in the path: xhtml2pdf/util.py

when a string: "<css function: var(--lwc-spacingxxxsmall. ('0.25'. 'rem'))>" is passed to the getSize function.

Need help in resolving this issue.

Full stack trace:

2023-12-18 06:19 - xhtml2pdf - ThreadPoolExecutor-0_0  - SpawnProcess-4 - DEBUG - [document.py:99] pisaDocument options:
  src = <_io.BufferedReader name='./output/lob2358069041046861738.HTML'>
  dest = <_io.BufferedWriter name='./output/temp_document_converted_file.pdf'>
  path = None
  link_callback = None
  xhtml = False
  context_meta = None
2023-12-18 06:19 - xhtml2pdf - ThreadPoolExecutor-0_0  - SpawnProcess-4 - WARNING - [util.py:295] getSize <CSS function: var(--lwc-varSpacingXxSmall, ('0.25', 'rem'))> 9.75
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/xhtml2pdf/util.py", line 287, in getSize
    return max(MIN_FONT_SIZE, relative * float(value))
ValueError: could not convert string to float: "<css function: var(--lwc-varspacingxxsmall. ('0.25'. 'rem'))>"