Lab theme handling

setup.cfg

@@ -33,9 +33,10 @@ packages = find:
 python_requires = >=3.7
 install_requires =
     jupyter_server>=0.3.0,<2.0.0
+    jupyterlab_server>=2.3.0,<3
     jupyter_client>=6.1.3,<8
     nbclient>=0.4.0,<0.6
-    nbconvert>=6.0.0,<7
+    nbconvert>=6.4.2,<7
     websockets>=9.0
     traitlets>=5.0.3,<6
 

share/jupyter/voila/templates/lab/page.html

@@ -8,6 +8,7 @@
     {{ include_css("static/index.css") }}
     {{ include_css("static/theme-light.css") }}
 {% else %}
-<!-- TODO: Use custom css from theme labextension -->
+    {{ include_css("static/index.css") }}
+    {{ include_lab_theme(theme) }}
 {% endif %}
 {% endblock %}

voila/app.py

@@ -44,6 +44,8 @@
 from jupyter_server.utils import url_path_join, run_sync
 from jupyter_server.services.config import ConfigManager
 
+from jupyterlab_server.themes_handler import ThemesHandler
+
 from jupyter_client.kernelspec import KernelSpecManager
 
 from jupyter_core.paths import jupyter_config_path, jupyter_path
@@ -481,6 +483,16 @@ def start(self):
                     'default_filename': 'index.html'
                 },
             ),
+            (
+                url_path_join(self.server_url, r'/voila/themes/(.*)'),
+                ThemesHandler,
+                {
+                    'themes_url': '/voila/themes',
+                    'path': '',
+                    'labextensions_path': jupyter_path('labextensions'),
+                    'no_cache_paths': ['/']
+                },
+            ),
             (url_path_join(self.server_url, r'/voila/api/shutdown/(.*)'), VoilaShutdownKernelHandler)
         ])
 

voila/server_extension.py

@@ -15,6 +15,8 @@
 from jupyter_server.utils import url_path_join
 from jupyter_server.base.handlers import path_regex, FileFindHandler
 
+from jupyterlab_server.themes_handler import ThemesHandler
+
 from .paths import ROOT, collect_template_paths, collect_static_paths, jupyter_path
 from .handler import VoilaHandler
 from .treehandler import VoilaTreeHandler
@@ -67,6 +69,16 @@ def _load_jupyter_server_extension(server_app):
         (url_path_join(base_url, '/voila'), VoilaTreeHandler, tree_handler_conf),
         (url_path_join(base_url, '/voila/tree' + path_regex), VoilaTreeHandler, tree_handler_conf),
         (url_path_join(base_url, '/voila/templates/(.*)'), TemplateStaticFileHandler),
+        (
+            url_path_join(base_url, r'/voila/themes/(.*)'),
+            ThemesHandler,
+            {
+                'themes_url': '/voila/themes',
+                'path': '',
+                'labextensions_path': jupyter_path('labextensions'),
+                'no_cache_paths': ['/']
+            },
+        ),
         (url_path_join(base_url, '/voila/static/(.*)'), MultiStaticFileHandler, {'paths': static_paths}),
         (url_path_join(base_url, r'/voila/api/shutdown/(.*)'), VoilaShutdownKernelHandler),
         (

voila/utils.py

@@ -18,6 +18,10 @@
 
 import jinja2
 
+from nbconvert.exporters.html import find_lab_theme
+
+from jupyterlab_server.themes_handler import ThemesHandler
+
 from .static_file_handler import TemplateStaticFileHandler
 
 
@@ -125,9 +129,24 @@ def include_url(template_name, base_url, name):
     return jinja2.Markup(make_url(template_name, base_url, name))
 
 
+def include_lab_theme(base_url, name):
+    # Try to find the theme with the given name, looking through the labextensions
+    theme_name, _ = find_lab_theme(name)
+
+    settings = {
+        'static_url_prefix': f'{base_url}voila/themes/',
+        'static_path': None  # not used in TemplateStaticFileHandler.get_absolute_path
+    }
+    url = ThemesHandler.make_static_url(settings, f'{theme_name}/index.css')
+
+    code = f'<link rel="stylesheet" type="text/css" href="{url}">'
+    return jinja2.Markup(code)
+
+
 def create_include_assets_functions(template_name, base_url):
     return {
         "include_css": partial(include_css, template_name, base_url),
         "include_js": partial(include_js, template_name, base_url),
-        "include_url": partial(include_url, template_name, base_url)
+        "include_url": partial(include_url, template_name, base_url),
+        "include_lab_theme": partial(include_lab_theme, base_url)
     }