Support for Mermaid Diagrams using ReLaXed JS

Add option to use 'ReLaXeD' JS renderer for PDF
instead of Headless Chrome.

option added: use_relaxed_js_renderer

option changed:
 - output_pdf_name: default 'document' as before
 - output_path:     contains now only directory name
                    not a file name

Issue orzih#34

README.md

@@ -225,6 +225,21 @@ plugins:
 >    <ANY_SITE_URL(eg. 'https://google.com')>
 > ```
 
+* `use_relaxed_js_renderer`
+
+    Set the value to `true` if you're using e.g. '[Mermaid](https://mermaid-js.github.io) diagrams and Headless Chrome is not working for you.
+    Require "ReLaXed" Javascript PDF renderer to be installed on your system. See: '[ReLaXed](https://github.com/RelaxedJS/ReLaXed)'.
+
+    Please use 'theme_handler_path' option to specify custom JS sources and CSS Stylesheets which covers your needs. E.g. for Material
+    theme it would be **material.py**. See: **mkdocs-with-pdf/mkdocs_with_pdf/themes/material.py** for implementation details.
+    **default**: `false`
+
+> Install on your system:
+> ```
+> $ npm i -g relaxedjs
+> $ relaxed --version
+> ```
+
 ##### ... and more
 
 * `output_path`

mkdocs_with_pdf/generator.py

@@ -1,6 +1,7 @@
 import logging
 import os
 import re
+import subprocess
 from importlib import import_module
 from importlib.util import module_from_spec, spec_from_file_location
 
@@ -123,15 +124,24 @@ def add_stylesheet(stylesheet: str):
         if self._options.debug_html:
             print(f'{html_string}')
 
-        self.logger.info("Rendering for PDF.")
-        html = HTML(string=html_string)
-        render = html.render()
-
         abs_pdf_path = os.path.join(config['site_dir'], output_path)
+        output_pdf_name = self._options.output_pdf_name
         os.makedirs(os.path.dirname(abs_pdf_path), exist_ok=True)
 
+        self.logger.info("Rendering for PDF.")
         self.logger.info(f'Output a PDF to "{abs_pdf_path}".')
-        render.write_pdf(abs_pdf_path)
+
+        if self._options.use_relaxed_js_renderer:
+            self.logger.info("Use 'Relaxed' JS renderer.")
+            output_html_name = os.path.join(abs_pdf_path, output_pdf_name + '.html')
+            with open(output_html_name, 'w+') as f:
+                f.write(html_string)
+                f.close()
+            subprocess.call(["relaxed", output_html_name, "--build-once"])
+        else:
+            html = HTML(string=html_string)
+            render = html.render()
+            render.write_pdf(abs_pdf_path + output_pdf_name + ".pdf")
 
     # ------------------------
     def _remove_empty_tags(self, soup: PageElement):
@@ -351,4 +361,8 @@ def _render_js(self, soup):
             if body:
                 for src in scripts:
                     body.append(soup.new_tag('script', src=f'file://{src}'))
-        return self._options.js_renderer.render(str(soup))
+
+        if self._options.use_relaxed_js_renderer:
+            return str(soup)
+        else:
+            return self._options.js_renderer.render(str(soup))

mkdocs_with_pdf/options.py

@@ -21,7 +21,8 @@ class Options(object):
         ('debug_html', config_options.Type(bool, default=False)),
         ('show_anchors', config_options.Type(bool, default=False)),
 
-        ('output_path', config_options.Type(str, default="pdf/document.pdf")),
+        ('output_pdf_name', config_options.Type(str, default="document")),
+        ('output_path', config_options.Type(str, default="pdf/")),
         ('theme_handler_path', config_options.Type(str, default=None)),
 
         ('author', config_options.Type(str, default=None)),
@@ -43,7 +44,9 @@ class Options(object):
 
         ('render_js', config_options.Type(bool, default=False)),
         ('headless_chrome_path',
-            config_options.Type(str, default='chromium-browser'))
+            config_options.Type(str, default='chromium-browser')),
+        ('use_relaxed_js_renderer',
+            config_options.Type(bool, default=False)),
     )
 
     def __init__(self, local_config, config, logger: logging):
@@ -54,6 +57,7 @@ def __init__(self, local_config, config, logger: logging):
         self.show_anchors = local_config['show_anchors']
 
         self.output_path = local_config.get('output_path', None)
+        self.output_pdf_name = local_config.get('output_pdf_name', None)
         self.theme_handler_path = local_config.get('theme_handler_path', None)
 
         # Author and Copyright
@@ -85,6 +89,11 @@ def __init__(self, local_config, config, logger: logging):
 
         self.two_columns_level = local_config['two_columns_level']
 
+        if local_config['use_relaxed_js_renderer']:
+            self.use_relaxed_js_renderer = True
+        else:
+            self.use_relaxed_js_renderer = False
+
         # ...etc.
         self.js_renderer = None
         if local_config['render_js']: