css: Support for dark mode

Modern browsers have a "dark mode" preference, which enables alternate
styles on web sites that support this.

This patch adds a dark color scheme, that is automatically activated
via a CSS @media query.

Older browsers that do not support color schemes will simply show the
light scheme, but possibly without syntax highlighting.

Note that filters that use color (such as source highlighters) and
logotypes may need to be updated to work with a black background!
See the updated files in the filters/ directory.

Signed-off-by: Samuel Lidén Borell <samuel@kodafritt.se>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 28 insertions, 2 deletions

diff --git a/filters/html-converters/md2html b/filters/html-converters/md2html
index 59f43a8..627808a 100755
--- a/filters/html-converters/md2html
+++ b/filters/html-converters/md2html
@@ -4,6 +4,11 @@ import sys
 import io
 from pygments.formatters import HtmlFormatter
 from markdown.extensions.toc import TocExtension
+
+# The dark style is automatically selected if the browser is in dark mode
+light_style='pastie'
+dark_style='monokai'
+
 sys.stdin = io.TextIOWrapper(sys.stdin.buffer, encoding='utf-8')
 sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-8')
 sys.stdout.write('''
@@ -283,10 +288,31 @@ div#cgit .markdown-body h1 a.toclink, div#cgit .markdown-body h2 a.toclink, div#
     background-color: transparent;
     border: none;
 }
+@media only all and (prefers-color-scheme: dark) {
+.markdown-body a.absent { color: #f33; }
+.markdown-body h1 .mini-icon-link, .markdown-body h2 .mini-icon-link, .markdown-body h3 .mini-icon-link, .markdown-body h4 .mini-icon-link, .markdown-body h5 .mini-icon-link, .markdown-body h6 .mini-icon-link { color: #eee; }
+div#cgit .markdown-body h1 a.toclink, div#cgit .markdown-body h2 a.toclink, div#cgit .markdown-body h3 a.toclink, div#cgit .markdown-body h4 a.toclink, div#cgit .markdown-body h5 a.toclink, div#cgit .markdown-body h6 a.toclink { color: #eee; }
+.markdown-body h1 { color: #eee; }
+.markdown-body h2 { border-bottom-color: #333; color: #eee; }
+.markdown-body h6 { color: #888; }
+.markdown-body hr { border-color: #333; }
+.markdown-body blockquote { border-left-color: #222; color: #888; }
+.markdown-body table th, .markdown-body table td { border-color: #333; }
+.markdown-body table tr { border-top-color: #333; background-color: #111; }
+.markdown-body table tr:nth-child(2n) { background-color: #070707; }
+.markdown-body span.frame span span { color: #ccc; }
+.markdown-body code, .markdown-body tt { border-color: #151515; background-color: #070707; }
+.markdown-body .highlight pre, .markdown-body pre { background-color: #070707; border-color: #333; }
 ''')
-sys.stdout.write(HtmlFormatter(style='pastie').get_style_defs('.highlight'))
+sys.stdout.write(HtmlFormatter(style=dark_style).get_style_defs('.highlight'))
 sys.stdout.write('''
-</style>   
+}
+@media (prefers-color-scheme: light) {
+''')
+sys.stdout.write(HtmlFormatter(style=light_style).get_style_defs('.highlight'))
+sys.stdout.write('''
+}
+</style>
 ''')
 sys.stdout.write("<div class='markdown-body'>")
 sys.stdout.flush()