getCSSRules: Find the CSS element that applies to an XML/HTML node

In omegahat/RCSS: Facilities for reading and working with CSS files in R

Description

This is the function that allows us to lookup/resolve the CSS element that would apply to a particular XML/HTML element. We can take XML nodes created using the XML package.

Usage

getCSSRules(nodes, sheet, eng = NULL)

Arguments

nodes	an object of class XMLInternalNode for which we want to find the applicable CSS element(s).
sheet	the CSSStyleSheet-class in which to resolve the CSS element(s) for the given node.
eng	the CSS selection engine. This can be created once and used in multiple, separate calls to this function. This will improve performance marginally.

Value

A list of CSSStatement objects.

Author(s)

Duncan Temple Lang

References

libcroco at http://www.freespiders.org/projects/libcroco Cascading Style Sheets http://www.w3.org/Style/CSS/

See Also

readCSS xmlParse, getNodeSet, newXMLNode asCSSObject

Examples

css = readCSS( system.file("samples", "OmegaTech.css", package =  "RCSS"))

if(require(XML)) {
 b = newXMLNode("BODY")
 code = newXMLNode("code", attrs = c(class = "r"))
 rules = getCSSRules(b, css)

 x = asCSSObject(rules[[1]])
}

if(require(XML)) {
  css = readCSS( system.file("samples", "descendant.css", package =  "RCSS"))

  node = newXMLNode("a", newXMLNode("b", newXMLNode("c", "some text")))
     # nothing matches the top-level node "a"
  getCSSRules(node, css)
     # for b we get the match a > b
  r = getCSSRules(node[[1]], css)
  asCSSObject(r[[1]])

     # a c
  r = getCSSRules(node[[1]][[1]], css)
  asCSSObject(r[[1]])

   # All the nodes in a document.
  doc = newXMLDoc(node = node, addFinalizer = FALSE)
  allNodes = getNodeSet(doc, "//*")
  lapply(allNodes, getCSSRules, css)

  # We can create the selection engine just once

  eng = .Call("R_createSelectionEngine")
  lapply(allNodes, getCSSRules, css, eng)
}

omegahat/RCSS documentation built on May 24, 2019, 1:52 p.m.