| to_html {fansi} | R Documentation |
Convert Control Sequences to HTML Equivalents
Description
Interprets CSI SGR sequences and OSC hyperlinks to produce strings with
the state reproduced with SPAN elements, inline CSS styles, and A anchors.
Optionally for colors, the SPAN elements may be assigned classes instead of
inline styles, in which case it is the user's responsibility to provide a
style sheet. Input that contains special HTML characters ("<", ">", "&",
"'", and "\"") likely should be escaped with html_esc, and to_html will
warn if it encounters the first two.
Usage
to_html(
x,
warn = getOption("fansi.warn", TRUE),
term.cap = getOption("fansi.term.cap", dflt_term_cap()),
classes = FALSE,
carry = getOption("fansi.carry", TRUE)
)
Arguments
x |
a character vector or object that can be coerced to such. |
warn |
TRUE (default) or FALSE, whether to warn when potentially
problematic Control Sequences are encountered. These could cause the
assumptions |
term.cap |
character a vector of the capabilities of the terminal, can
be any combination of "bright" (SGR codes 90-97, 100-107), "256" (SGR codes
starting with "38;5" or "48;5"), "truecolor" (SGR codes starting with
"38;2" or "48;2"), and "all". "all" behaves as it does for the |
classes |
FALSE (default), TRUE, or character vector of either 16, 32, or 512 class names. Character strings may only contain ASCII characters corresponding to letters, numbers, the hyphen, or the underscore. It is the user's responsibility to provide values that are legal class names.
|
carry |
TRUE, FALSE (default), or a scalar string, controls whether to
interpret the character vector as a "single document" (TRUE or string) or
as independent elements (FALSE). In "single document" mode, active state
at the end of an input element is considered active at the beginning of the
next vector element, simulating what happens with a document with active
state at the end of a line. If FALSE each vector element is interpreted as
if there were no active state when it begins. If character, then the
active state at the end of the |
Details
Only "observable" formats are translated. These include colors, background-colors, and basic styles (CSI SGR codes 1-6, 8, 9). Style 7, the "inverse" style, is implemented by explicitly switching foreground and background colors, if there are any. Styles 5-6 (blink) are rendered as "text-decoration" but likely will do nothing in the browser. Style 8 (conceal) sets the color to transparent.
Parameters in OSC sequences are not copied over as they might have different semantics in the OSC sequences than they would in HTML (e.g. the "id" parameter is intended to be non-unique in OSC).
Each element of the input vector is translated into a stand-alone valid HTML
string. In particular, any open tags generated by fansi are closed at the
end of an element and re-opened on the subsequent element with the same
style. This allows safe combination of HTML translated strings, for example
by pasteing them together. The trade-off is that there may be redundant
HTML produced. To reduce redundancy you can first collapse the input vector
into one string, being mindful that very large strings may exceed maximum
string size when converted to HTML.
fansi-opened tags are closed and new ones open anytime the "observable"
state changes. to_html never produces nested tags, even if at times
that might produce more compact output. While it would be possible to
match a CSI/OSC encoded state with nested tags, it would increase the
complexity of the code substantially for little gain.
Value
A character vector of the same length as x with all escape
sequences removed and any basic ANSI CSI SGR escape sequences applied via
SPAN HTML tags.
Note
Non-ASCII strings are converted to and returned in UTF-8 encoding.
to_html always terminates as not doing so produces
invalid HTML. If you wish for the last active SPAN to bleed into
subsequent text you may do so with e.g. sub("</span>(?:</a>)?$", "", x)
or similar. Additionally, unlike other functions, the default is
carry = TRUE for compatibility with semantics of prior versions of
fansi.
See Also
Other HTML functions:
html_esc(),
in_html(),
make_styles()
Examples
to_html("hello\033[31;42;1mworld\033[m")
to_html("hello\033[31;42;1mworld\033[m", classes=TRUE)
## Input contains HTML special chars
x <- "<hello \033[42m'there' \033[34m &\033[m \"moon\"!"
writeLines(x)
## Not run:
in_html(
c(
to_html(html_esc(x)), # Good
to_html(x) # Bad (warning)!
) )
## End(Not run)
## Generate some class names for basic colors
classes <- expand.grid(
"myclass",
c("fg", "bg"),
c("black", "red", "green", "yellow", "blue", "magenta", "cyan", "white")
)
classes # order is important!
classes <- do.call(paste, c(classes, sep="-"))
## We only provide 16 classes, so Only basic colors are
## mapped to classes; others styled inline.
to_html(
"\033[94mhello\033[m \033[31;42;1mworld\033[m",
classes=classes
)
## Create a whole web page with a style sheet for 256 colors and
## the colors shown in a table.
class.256 <- do.call(paste, c(expand.grid(c("fg", "bg"), 0:255), sep="-"))
sgr.256 <- sgr_256() # A demo of all 256 colors
writeLines(sgr.256[1:8]) # SGR formatting
## Convert to HTML using classes instead of inline styles:
html.256 <- to_html(sgr.256, classes=class.256)
writeLines(html.256[1]) # No inline colors
## Generate different style sheets. See `?make_styles` for details.
default <- make_styles(class.256)
mix <- matrix(c(.6,.2,.2, .2,.6,.2, .2,.2,.6), 3)
desaturated <- make_styles(class.256, mix)
writeLines(default[1:4])
writeLines(desaturated[1:4])
## Embed in HTML page and diplay; only CSS changing
## Not run:
in_html(html.256) # no CSS
in_html(html.256, css=default) # default CSS
in_html(html.256, css=desaturated) # desaturated CSS
## End(Not run)