R/unclip.R

In ggtikz: Post-Process 'ggplot2' Plots with 'TikZ' Code Using Plot Coordinates

#' Unclip a plot produced by the `tikzDevice`.
#'
#' By default, plots produced with the tikzDevice are clipped to the plot area,
#' which also clips ggtikzAnnotations extending beyond the plot boundaries. This
#' function removes the 'clip' and 'use as bounding box' options in a tikz file.
#'
#' This function can be used for manual post-processing, however,
#' see \code{\link{set_ggtikz_unclip_hook}} to set the corresponding knitr hook.
#'
#' @param fpath Path to the tikz file
#'
#' @returns Called for side effect.
#'  The file at `fpath` is edited and overwritten.
#'
#' @seealso \code{\link{set_ggtikz_unclip_hook}} to set the knitr hook.
#'
#' @export
unclip_tikz <- function(fpath) {
    lines <- readLines(fpath)
    new <- lines

    # Remove definition of explicit bounding box: use space as required
    bblines <- grep("use as bounding box", lines)
    if (length(bblines) > 0) {
        new <- new[-bblines]

        # First 'use as bounding box' option we find has the coordinates of the
        # complete plot area. In this command, the origin is formatted as (0,0),
        # whereas in other clip commands, it is formatted by "%6.2f,%6.2f" (see
        # tikzDevice.c of the tikzDevice package)
        bbline <- lines[bblines[1]]
        cliprect <- regmatches(bbline, regexpr("rectangle [^;]*", bbline))
        clipstart <- sprintf("\\path[clip] (%6.2f,%6.2f)", 0, 0)
        clippat <- paste(clipstart, cliprect)

        plotcliplines <- grep(clippat, new, fixed=TRUE)
        if (length(plotcliplines) > 0) {
            new <- new[-plotcliplines]
        }
    }

    writeLines(new, fpath)
}


#' knitr hook to remove clipping from plots produced with the tikzDevice.
#'
#' Note that the chunk options `unclip = TRUE` and `external = FALSE`must be set
#' for the hook to come into effect!
#'
#' @param before see \code{\link[knitr]{knit_hooks}}
#' @param options see \code{\link[knitr]{knit_hooks}}
#'
#' @returns Called for side effect.
#'  The files containing tikz plots are edited and overwritten.
#'
#' @seealso \code{\link{set_ggtikz_unclip_hook}} to set the knitr hook.
#' @seealso \code{\link{unclip_tikz}}, the workhorse function for this hook.
#'
#' @export
unclip <- function(before, options) {
    if (!before & options$unclip != FALSE) {
        plot_files <- unique(knitr::opts_knit$get("plot_files"))
        ext_pattern <- tikz_exts_pattern(options)
        tikz_files <- grep(ext_pattern, plot_files, ignore.case = TRUE, value = TRUE)
        for (tikz_file in tikz_files) {
            unclip_tikz(tikz_file)
        }
    }
}


#' Construct a regex pattern for possible tikzDevice extensions.
#'
#' @param options A list of `knitr` chunk options
#'
#' @returns A regex pattern to match file extensions of tikz figures
tikz_exts_pattern <- function(options) {
    devs <- options$dev
    exts <- options$fig.ext
    if (is.null(exts)) {
        # the default
        exts <- "tex"
    } else {
        exts <- exts[which(devs == "tikz")]
    }
    pattern <- sprintf("[.](%s)",paste(exts, collapse="|"))
    return(pattern)
}


#' Unclip plots produced by the `tikzDevice`.
#'
#' By default, plots produced with the tikzDevice are clipped to the plot area,
#' which also clips ggtikzAnnotations extending beyond the plot boundaries. This
#' function removes the 'clip' and 'use as bounding box' options in a tikz file.
#'
#' @returns Called for side effects - the `unclip` knitr hook is set or unset,
#'  respectively.
#'
#' @seealso \code{\link{unclip}}, the hook that is being set.
#'
#' @export
set_ggtikz_unclip_hook <- function() {
    knitr::knit_hooks$set(unclip=unclip)
}

#' @rdname set_ggtikz_unclip_hook
#' @export
unset_ggtikz_unclip_hook <- function() {
    knitr::knit_hooks$set(unclip=NULL)
}