Missing icon and incorrect border for admonition in PDF output

Contribution guidelines

• I’ve read the contribution guidelines and wholeheartedly agree

I’ve found a bug and checked that …

• … the problem doesn’t occur with the mkdocs or readthedocs themes
• … the problem persists when all overrides are removed, i.e. custom_dir, extra_javascript and extra_css
• … the documentation does not mention anything about my problem
• … there are no open or closed issues that are related to my problem

Description

When using mkdocs-pdf-export-plugin, icons are no longer shown for admonitions in the PDF output since mkdocs-material rev b345a0b65 and the border does not look correct.

Expected behaviour

It should look like this (this is with c79b786ea):

Actual behaviour

But it looks like this (this is with master):

Note the lack of icon, and how the blue border extends all around the admonition.

Steps to reproduce

Test input test/docs/index.md (test/mkdocs.yml as below under Configuration)

# Welcome to MkDocs

!!! note
    This is a note

Incorrect behavior with master

python3 -m venv bad_env
source bad_env/bin/activate
pip install wheel
pip install mkdocs mkdocs-pdf-export-plugin git+ssh://[e-mail]/squidfunk/mkdocs-material.git
mkdocs build -f test/mkdocs.yml && xdg-open test/site/index.pdf

Correct behavior with rev c79b786ea

python3 -m venv good_env
source good_env/bin/activate
pip install wheel
pip install mkdocs mkdocs-pdf-export-plugin git+ssh://[e-mail]/squidfunk/mkdocs-material.git@c79b786ea
mkdocs build -f test/mkdocs.yml && xdg-open test/site/index.pdf

I git bisect:ed and the first bad commit seems to be b345a0b65:

b345a0b65 Prototyped material icon SVG integration

Package versions

• Python: 3.8.10
• MkDocs: 1.3.0 (git rev 7418e7961)
• Material: 4.6.3

Configuration

site_name: My Docs
theme:
  name: material
plugins:
  - pdf-export
markdown_extensions:
  - admonition

System information

• Operating system: Ubuntu 20.04.4 LTS
• Browser: Firefox 98.0.2 and Okular 1.9.3 for PDF viewing

[estan]

Turns out there was an open issue for mask-image support in weasyprint already: https://github.com/Kozea/WeasyPrint/issues/1458

[estan]

Thanks. I think this info will be of use. Possibly the place to fix is in weasyprint which the plugin is using.