grid.crosshair: Draw crosshairs with grid

In piecepackr: Board Game Graphics

Draw crosshairs with grid

Description

grid.crosshair() draws crosshairs at the corners of a rectangular area. crosshairGrob() is its grid grob counterpart. They are intended for use in adding crosshairs at the corners of game pieces in print-and-play layouts. One can also use the lower level circledSegmentsCrosshairGrob(), segmentsCrosshairGrob(), squaredSegmentsCrosshairGrob(), and squaresCrosshairGrob() (which can be drawn with grid::grid.draw()) to add individual crosshairs to specified (x,y) locations (e.g. for use as registration marks).

Usage

crosshairGrob(
  ...,
  piece_side = "tile_back",
  suit = NA,
  rank = NA,
  cfg = getOption("piecepackr.cfg", pp_cfg()),
  x = unit(0.5, "npc"),
  y = unit(0.5, "npc"),
  angle = 0,
  width = NA,
  height = NA,
  scale = 1,
  default.units = "npc",
  envir = getOption("piecepackr.envir"),
  name = NULL,
  gp = gpar(),
  vp = NULL,
  ch_width = unit(1/6, "in"),
  ch_grob = squaresCrosshairGrob()
)

grid.crosshair(..., draw = TRUE)

segmentsCrosshairGrob(
  ...,
  x = unit(0.5, "npc"),
  y = unit(0.5, "npc"),
  width = unit(1, "snpc"),
  height = unit(1, "snpc"),
  default.units = "npc",
  name = NULL,
  gp = gpar(),
  vp = NULL
)

circledSegmentsCrosshairGrob(
  ...,
  x = unit(0.5, "npc"),
  y = unit(0.5, "npc"),
  width = unit(1, "snpc"),
  height = unit(1, "snpc"),
  default.units = "npc",
  name = NULL,
  gp = gpar(),
  vp = NULL
)

squaredSegmentsCrosshairGrob(
  ...,
  x = unit(0.5, "npc"),
  y = unit(0.5, "npc"),
  width = unit(1, "snpc"),
  height = unit(1, "snpc"),
  default.units = "npc",
  name = NULL,
  gp = gpar(),
  vp = NULL
)

squaresCrosshairGrob(
  ...,
  x = unit(0.5, "npc"),
  y = unit(0.5, "npc"),
  width = unit(1, "snpc"),
  height = unit(1, "snpc"),
  default.units = "npc",
  name = NULL,
  gp = gpar(),
  vp = NULL
)

Arguments

...	crosshairGrob() ignores; grid.crosshair() passes to crosshairGrob().
piece_side	A string with piece and side separated by a underscore e.g. "coin_face"
suit	Number of suit (starting from 1).
rank	Number of rank (starting from 1)
cfg	Piecepack configuration list or pp_cfg object, a list of pp_cfg objects, or a character vector referring to names in envir or a character vector referring to object names that can be retrieved by base::dynGet().
x	Where to place piece on x axis of viewport
y	Where to place piece on y axis of viewport
angle	Angle (on xy plane) to draw piece at
width	Width of piece
height	Height of piece
scale	Multiplicative scaling factor to apply to width, height, and depth.
default.units	A string indicating the default units to use if 'x', 'y', 'width', and/or 'height' are only given as numeric vectors.
envir	Environment (or named list) containing configuration list(s).
name	A character identifier (for grid)
gp	An object of class “gpar”.
vp	A grid viewport object (or NULL).
ch_width	Width/height of ch_grob's viewport.
ch_grob	Crosshair grob. Will be drawn in each corner of the piece in a viewport with ch_width width and ch_width height. segmentsCrosshairGrob() simply wraps grid::segmentsGrob(). circledSegmentsCrosshairGrob() wraps grid::segmentsGrob() and grid::circleGrob(). squaredSegmentsCrosshairGrob() wraps grid::segmentsGrob() and grid::rectGrob(). squaresCrosshairGrob() wraps grid::rectGrob() and alternates black/white squares for visibility on both light and dark backgrounds.
draw	A logical value indicating whether graphics output should be produced.

Value

A grid grob.

Examples

if (requireNamespace("grid", quietly = TRUE) &&
    piecepackr:::device_supports_unicode()) {
  cfg <- pp_cfg(list(border_color = NA))
  grid::grid.newpage()
  df <- data.frame(piece_side = "tile_face", suit = 2, rank = 2,
                   x = 2, y = 2, angle = 0,
                   stringsAsFactors = FALSE)
  pmap_piece(df, grid.piece, cfg = cfg, default.units = "in")
  pmap_piece(df, grid.crosshair, cfg = cfg, default.units = "in")
}
if (requireNamespace("grid", quietly = TRUE) &&
    piecepackr:::device_supports_unicode()) {
  grid::grid.newpage()
  pmap_piece(df, grid.piece, cfg = cfg, default.units = "in")
  pmap_piece(df, grid.crosshair, cfg = cfg, default.units = "in",
             ch_grob = segmentsCrosshairGrob())
}
if (requireNamespace("grid", quietly = TRUE)) {
  grid::grid.newpage()
  fns <- list(squaresCrosshairGrob, segmentsCrosshairGrob,
              circledSegmentsCrosshairGrob, squaredSegmentsCrosshairGrob)
  labels <- c("squaresCrosshairGrob()", "segmentsCrosshairGrob()",
              "circledSegmentsCrosshairGrob()", "squaredSegmentsCrosshairGrob()")
  xs <- c(0.25, 0.75, 0.25, 0.75)
  ys <- c(0.70, 0.70, 0.30, 0.30)
  label_ys <- c(0.55, 0.55, 0.15, 0.15)
  for (i in seq_along(fns)) {
    grid::grid.draw(fns[[i]](x = grid::unit(xs[i], "npc"),
                             y = grid::unit(ys[i], "npc"),
                             width = grid::unit(0.15, "npc"),
                             height = grid::unit(0.15, "npc")))
    grid::grid.text(labels[i], x = xs[i], y = label_ys[i], gp = grid::gpar(cex = 0.7))
  }
}

piecepackr documentation built on May 12, 2026, 9:07 a.m.