conf: add support for a dark mode in the documentation

this commit adds support for a dark theme that behaves similarly to
that one used by the api viewer.

Signed-off-by: Stefan Sterz <s.sterz@proxmox.com>

asciidoc/pve-docs.css

@@ -0,0 +1,168 @@
+:root {
+    /* pre-defined colors */
+    --pdt-grey-950: hsl(0deg, 0%, 95%);
+    --pdt-grey-400: hsl(0deg, 0%, 40%);
+    --pdt-grey-250: hsl(0deg, 0%, 25%);
+    --pdt-grey-150: hsl(0deg, 0%, 15%);
+    --pdt-grey-100: hsl(0deg, 0%, 10%);
+    --pdt-primary-850: hsl(205deg, 100%, 85%);
+    --pdt-primary-800: hsl(205deg, 100%, 80%);
+    --pdt-primary-700: hsl(205deg, 100%, 70%);
+    --pdt-secondary-850: hsl(250deg, 100%, 85%);
+}
+
+/* adjust admonition block spacing. this allows for a background on
+ * admonition blocks that doesn't make the elements look to tightly
+ * spaced.
+ */
+div.admonitionblock {
+    border-radius: 3px;
+    margin: 1.5em 0;
+    padding: 0.5em 10% 0.5em 0.5em;
+}
+
+div.admonitionblock td.icon {
+    padding-right: 0.5em;
+}
+
+div.admonitionblock td.icon > img {
+    box-sizing: border-box;
+    padding: 0.15em;
+}
+
+@media screen and (prefers-color-scheme: dark) {
+    :root {
+        color-scheme: dark;
+        --pdt-body-background: var(--pdt-grey-150);
+        --pdt-text: var(--pdt-grey-950);
+        --pdt-headline: var(--pdt-primary-800);
+        --pdt-link: var(--pdt-primary-700);
+        --pdt-link-visited: var(--pdt-secondary-850);
+        --pdt-highlighted-text: var(--pdt-primary-850);
+        --pdt-background-sidebar: var(--pdt-grey-100);
+        --pdt-background-listings: var(--pdt-grey-100);
+        --pdt-border: var(--pdt-grey-400);
+        --pdt-border-alt: var(--pdt-grey-250);
+        --pdt-table-border: var(--pdt-grey-400);
+        --pdt-background-admonition: var(--pdt-grey-250);
+    }
+
+    body {
+        color: var(--pdt-text);
+        background-color: var(--pdt-body-background);
+    }
+
+    a {
+        color: var(--pdt-link);
+    }
+
+    a:visited {
+        color: var(--pdt-link-visited);
+    }
+
+    /* style headlines, titles etc. */
+    h1,
+    h2,
+    h3,
+    h4,
+    h5,
+    h6,
+    thead,
+    #author,
+    #toctitle,
+    div.title,
+    td.hdlist1,
+    caption.title,
+    p.tableblock.header {
+        color: var(--pdt-headline);
+    }
+
+    h1,
+    h2,
+    h3,
+    #footer {
+        border-color: var(--pdt-border);
+    }
+
+    /* formatted colored text */
+    dt,
+    em,
+    pre,
+    code,
+    strong,
+    .monospaced {
+        color: var(--pdt-highlighted-text);
+    }
+
+    /* style the table of contents sidebar */
+    div #toc {
+        color: var(--pdt-text);
+        background-color: var(--pdt-background-sidebar);
+        border-color: var(--pdt-border-alt);
+    }
+
+    div #toc a:link,
+    div #toc a:visited {
+        color: var(--pdt-text);
+    }
+
+    /* reduce the brigthness of images a bit and make it reversable
+     * through hovering over them.
+     */
+    .image > img {
+        filter: brightness(90%);
+    }
+
+    .image > img:hover {
+        filter: none;
+    }
+
+    /* tables */
+    th.tableblock,
+    td.tableblock,
+    table.tableblock {
+        border-color: var(--pdt-table-border);
+    }
+
+    div.quoteblock,
+    div.verseblock {
+        color: var(--pdt-text);
+        border-color: var(--pdt-border);
+    }
+
+    /* listings (e.g. code snippet blocks) */
+    div.listingblock > div.content {
+        background-color: var(--pdt-background-listings);
+        border-color: var(--pdt-border-alt);
+    }
+
+    /* admonition blocks (e.g. notes, warnings etc.) */
+    div.admonitionblock {
+        color: var(--pdt-text);
+        background-color: var(--pdt-background-admonition);
+    }
+
+    div.admonitionblock td.content {
+        border-color: var(--pdt-border);
+    }
+
+    /* makes the admonition icons appear a bit more consistent, by
+     * adding a white background the shadows in the icons look
+     * "correct"
+     */
+    div.admonitionblock td.icon > img {
+        background-color: white;
+        border-radius: 100%;
+        filter: brightness(95%);
+    }
+
+    /* invert the logo */
+    #header > h1 > .image > img {
+        filter: invert(100%) hue-rotate(180deg) brightness(90%);
+    }
+
+    /* fixes the black text on unorderd lists */
+    ul > li > * {
+        color: var(--pdt-text);
+    }
+}

asciidoc/pve-html.conf

@@ -629,6 +629,10 @@ div .toclevel1 {
 </style>
 endif::toc2[]
 
+<style type="text/css">
+include1::{stylesdir=.}/pve-docs.css[]
+</style>
+
 ifndef::disable-javascript[]
 ifdef::linkcss[]
 <script type="text/javascript" src="{scriptsdir=.}/asciidoc.js"></script>