R/units.R

In gridmicrotex: Native 'LaTeX' Math Rendering for Grid Graphics

#' Convert TeX points to big points
#'
#' TeX points (1/72.27 inch) differ from PostScript/big points (1/72 inch).
#' R's grid "bigpts" unit uses PostScript points.
#'
#' @param tex_pt Numeric value in TeX points.
#' @return Numeric value in big (PostScript) points.
#' @keywords internal
tex_pt_to_bigpt <- function(tex_pt) {
  tex_pt * (72 / 72.27)
}

#' Convert big points to TeX points
#'
#' @param big_pt Numeric value in PostScript points.
#' @return Numeric value in TeX points.
#' @keywords internal
bigpt_to_tex_pt <- function(big_pt) {
  big_pt * (72.27 / 72)
}

# Convert a grid-style lineheight multiplier to MicroTeX's line_space
# (extra gap between lines, in big points). Mirrors grid semantics:
# total line height = fontsize * lineheight.
.line_space_from_lineheight <- function(lineheight, fontsize) {
  if (is.null(lineheight)) lineheight <- 1.2
  if (is.null(fontsize) || fontsize <= 0) return(0)
  max(0, (lineheight - 1) * fontsize)
}