.\" Automatically generated by Pandoc 3.6.1 .\" .TH "cha\-css" "7" "" "" "Image support in Chawan" .SH CSS in Chawan This document describes some proprietary CSS extensions supported by Chawan, as well as its intentional deviations from standards. .PP If you discover a deviation that is not covered by this document, then please open a ticket at \c .UR https://todo.sr.ht/~bptato/chawan .UE \c \&. .SS Proprietary extensions .IP \[bu] 2 \f[CR]text\-align\f[R] accepts the values \f[CR]\-cha\-center\f[R], \f[CR]\-cha\-left\f[R], and \f[CR]\-cha\-right\f[R] to support the HTML \f[CR]
\f[R], \f[CR]
\f[R] and \f[CR]
\f[R] elements. (Analogous to \f[CR]\-moz\-center\f[R] etc.) .IP \[bu] 2 Properties with a \f[CR]\f[R] value accept the function \f[CR]\-cha\-ansi()\f[R], which takes one parameter that is either: .IP \[bu] 2 An 8\-bit integer, indicating a color value as set by XTerm\[cq]s indexed color feature. .IP \[bu] 2 One of the strings \[lq]black\[rq], \[lq]red\[rq], \[lq]green\[rq], \[lq]yellow\[rq], \[lq]blue\[rq], \[lq]magenta\[rq], \[lq]cyan\[rq], \[lq]white\[rq] for an ANSI color, possibly prefixed by the string \[lq]bright\-\[rq] to indicate an aixterm 16\-color value. .PP The actual palette in use is specified by the user/terminal. .IP \[bu] 2 \f[CR]text\-decoration\f[R] accepts the keyword \f[CR]\-cha\-reverse\f[R], which sets the \f[I]reverse video\f[R] parameter on the text. (This is used by the UA style sheet to highlight text in \f[CR]\f[R] tags.) .IP \[bu] 2 \f[CR]text\-transform\f[R] accepts the keyword \f[CR]\-cha\-half\-width\f[R], which has the opposite effect as \f[CR]full\-width\f[R]. This can be used in user style sheets to compress distracting ruby text: \f[CR]rt{text\-transform: \-cha\-half\-width}\f[R]. Characters without half\-width counterparts are left intact, except hiragana is treated as katakana. .IP \[bu] 2 The \f[CR]\-cha\-colspan\f[R] and \f[CR]\-cha\-rowspan\f[R] properties have the same effect as the \f[CR]colspan\f[R] and \f[CR]rowspan\f[R] attributes on tables. .IP \[bu] 2 The \f[CR]\-cha\-first\-node\f[R] and \f[CR]\-cha\-last\-node\f[R] selectors apply to elements that have no preceding/subsequent sibling node that is either an element node or a text node with non\-whitespace contents. (Modeled after \f[CR]\-moz\-first\-node\f[R] and \f[CR]\-moz\-last\-node\f[R].) .SS Rendering quirks These are willful violations of the standard, usually made to better fit the display model inherent to projecting the web to a cell\-based screen. .SS User agent style sheet The user agent style sheet is a combination of the styles suggested by the HTML standard and a CSS port of w3m\[cq]s rendering. In general, faithfulness to w3m is preferred over the standard, unless it breaks existing websites. .PP Link colors differ depending on the terminal\[cq]s color scheme. .SS Sizing and positioning Layout is performed on a finite canvas of coordinates represented by a 32\-bit fixed\-point number with 6 bits of precision. After layout, these positions are divided by the cell width and/or height, with the fractional part truncated. (This is subject to change.) .PP In case of Kitty images, the fractional part is preserved, and is used as an in\-cell offset. .PP The lengths \f[CR]1em\f[R] and \f[CR]1ch\f[R] compute to the cell height and cell width respectively. .PP In outer inline boxes (\f[CR]inline\-block\f[R], \f[CR]inline\-flex\f[R]), margins and padding that are smaller than one cell (on the respective axis) are ignored. This does not apply to blockified inline boxes. .PP When calculating clip boxes (\f[CR]overflow: hidden\f[R] or \f[CR]clip\f[R]), the clip box\[cq]s offset is floored, and its size is ceiled to the nearest cell\[cq]s boundaries. This means that \[lq]width: 1px; overflow: hidden\[rq] will still display the first character of a text box. .SS Scroll bars Chawan does not have scroll bars, as they would complicate on\-page navigation and would not work in dump mode. Instead, the \[lq]overflow\-x/y\[rq] properties are handled as follows. .IP "1." 3 If \f[CR]overflow\f[R] is \f[CR]auto\f[R] or \f[CR]scroll\f[R], and the intrinsic minimum size of the box is greater than its specified size, then the former overrides the latter. .IP "2." 3 Content that spills out of a scroll container on the X axis is displayed, while content that spills out of a scroll container on the Y axis is clipped. .SS \f[CR]position: fixed\f[R], \f[CR]position: sticky\f[R] To keep the document model static, these do not change their position based on the viewport\[cq]s scroll status. Instead: .IP \[bu] 2 \f[CR]position: sticky\f[R] is treated as \f[CR]position: static\f[R], except it also behaves as an absolute position container. .IP \[bu] 2 \f[CR]position: fixed\f[R] is placed at the bottom of the document. .PP Right now, \f[CR]position: fixed\f[R] is always positioned at the bottom of the root element\[cq]s margin box. This breaks on pages that overflow it (e.g. by setting \f[CR]height: 100%\f[R] on the root element), so it will be moved to the bottom of its overflow box in the future. .SS Color correction Some authors only specify one of the foreground or the background color, assuming a black\-on\-white canvas. The \f[CR]display.minimum\-contrast\f[R] option adjusts the foreground color so that text remains readable even if the terminal background does not match this expectation. (The exact algorithm is unspecified and subject to change.) .PP This unfortunately breaks spoiler mechanisms that rely on \[lq]black on black\[rq] text not being visible. The issue disappears when \f[CR]visibility: hidden\f[R] is applied to the text as well. .SS See also \f[B]cha\f[R](1)