[fix] Made dark syntax highlighting follow the theme toggle

nemesifier · nemesifier · commit 850d9d73442d · 2026-06-16T15:40:22.000-03:00
Sphinx 9 and sphinxawesome-theme 6 gate the dark Pygments palette on
`@media (prefers-color-scheme: dark)`, both in the block appended to
pygments.css and in the separately media-linked pygments_dark.css.

The theme, however, toggles dark mode with a `.dark` class on &lt;html&gt;
that is persisted in localStorage and can diverge from the OS
preference (for example the site is kept dark while the OS turns
light at dawn). The code blocks therefore switched palette
independently of the rest of the page, producing low-contrast,
unreadable syntax highlighting.

Re-scope the dark palette under `.dark` so the syntax colors track
the same toggle as the rest of the theme.
diff --git a/conf.py b/conf.py
@@ -508,10 +508,13 @@
 
 
 def write_pygments_dark_css(app, exception):
-    """Write the dark Pygments stylesheet expected by Sphinx 9.
+    """Re-scope the dark Pygments palette under the theme's `.dark` class.
 
-    sphinxawesome-theme appends dark styles to pygments.css, but Sphinx 9
-    links pygments_dark.css separately when a dark Pygments style is set.
+    Runs on ``build-finished`` for HTML builds: drops the
+    ``@media (prefers-color-scheme: dark)`` block from ``pygments.css`` so only
+    the light palette remains, then appends the dark palette scoped under
+    ``.dark .highlight``. The separately linked ``pygments_dark.css`` is emptied
+    so it cannot apply the dark palette on its own.
     """
     if exception or app.builder.format != "html":
         return
@@ -520,9 +523,14 @@ def write_pygments_dark_css(app, exception):
         return
     static_dir = Path(app.outdir) / "_static"
     static_dir.mkdir(exist_ok=True)
-    (static_dir / "pygments_dark.css").write_text(
-        dark_highlighter.get_stylesheet(), encoding="utf-8"
-    )
+    pygments_css = static_dir / "pygments.css"
+    light = pygments_css.read_text(encoding="utf-8")
+    light = light.split("@media (prefers-color-scheme: dark)", 1)[0].rstrip()
+    dark = dark_highlighter.get_formatter().get_style_defs(".dark .highlight")
+    pygments_css.write_text(light + "\n" + dark + "\n", encoding="utf-8")
+    # Neutralize the separately media-linked dark stylesheet so it cannot apply
+    # the dark palette based on the OS preference.
+    (static_dir / "pygments_dark.css").write_text("", encoding="utf-8")
 
 
 def setup(app):
