R/geom-.R

In tidyverse/ggplot2: Create Elegant Data Visualisations Using the Grammar of Graphics

#' @include legend-draw.R
#' @include utilities-checks.R
NULL

#' @section Geoms:
#'
#' All `geom_*()` functions (like `geom_point()`) return a layer that
#' contains a `Geom*` object (like `GeomPoint`). The `Geom*`
#' object is responsible for rendering the data in the plot.
#'
#' Each of the `Geom*` objects is a [ggproto()] object, descended
#' from the top-level `Geom`, and each implements various methods and
#' fields.
#'
#' Compared to `Stat` and `Position`, `Geom` is a little
#' different because the execution of the setup and compute functions is
#' split up. `setup_data` runs before position adjustments, and
#' `draw_layer()` is not run until render time, much later.
#'
#' To create a new type of Geom object, you typically will want to
#' override one or more of the following:
#'
#'   - Either `draw_panel(self, data, panel_params, coord)` or
#'     `draw_group(self, data, panel_params, coord)`. `draw_panel` is
#'     called once per panel, `draw_group` is called once per group.
#'
#'     Use `draw_panel` if each row in the data represents a
#'     single element. Use `draw_group` if each group represents
#'     an element (e.g. a smooth, a violin).
#'
#'     `data` is a data frame of scaled aesthetics.
#'
#'     `panel_params` is a set of per-panel parameters for the
#'     `coord`. Generally, you should consider `panel_params`
#'     to be an opaque data structure that you pass along whenever you call
#'     a coord method.
#'
#'     You must always call `coord$transform(data, panel_params)` to
#'     get the (position) scaled data for plotting. To work with
#'     non-linear coordinate systems, you typically need to convert into a
#'     primitive geom (e.g. point, path or polygon), and then pass on to the
#'     corresponding draw method for munching.
#'
#'     Must return a grob. Use [zeroGrob()] if there's nothing to
#'     draw.
#'   - `draw_key`: Renders a single legend key.
#'   - `required_aes`: A character vector of aesthetics needed to
#'     render the geom.
#'   - `default_aes`: A list (generated by [aes()] of
#'     default values for aesthetics.
#'   - `setup_data`: Converts width and height to xmin and xmax,
#'     and ymin and ymax values. It can potentially set other values as well.
#'
#' See also the `r link_book("new geoms section", "extensions#sec-new-geoms")`
#' @rdname ggplot2-ggproto
#' @format NULL
#' @usage NULL
#' @export
Geom <- ggproto("Geom",
  required_aes = character(),
  non_missing_aes = character(),
  optional_aes = character(),

  default_aes = aes(),

  draw_key = draw_key_point,

  handle_na = function(self, data, params) {
    remove_missing(data, params$na.rm,
      c(self$required_aes, self$non_missing_aes),
      snake_class(self)
    )
  },

  draw_layer = function(self, data, params, layout, coord) {
    if (empty(data)) {
      n <- if (is.factor(data$PANEL)) nlevels(data$PANEL) else 1L
      return(rep(list(zeroGrob()), n))
    }

    # Trim off extra parameters
    params <- params[intersect(names(params), self$parameters())]

    if (nlevels(as.factor(data$PANEL)) > 1L) {
      data_panels <- split(data, data$PANEL)
    } else {
      data_panels <- list(data)
    }
    lapply(data_panels, function(data) {
      if (empty(data)) return(zeroGrob())

      panel_params <- layout$panel_params[[data$PANEL[1]]]
      inject(self$draw_panel(data, panel_params, coord, !!!params))
    })
  },

  draw_panel = function(self, data, panel_params, coord, ...) {
    groups <- split(data, factor(data$group))
    grobs <- lapply(groups, function(group) {
      self$draw_group(group, panel_params, coord, ...)
    })

    ggname(snake_class(self), gTree(
      children = inject(gList(!!!grobs))
    ))
  },

  draw_group = function(self, data, panel_params, coord) {
    cli::cli_abort("{.fn {snake_class(self)}}, has not implemented a {.fn draw_group} method")
  },

  setup_params = function(data, params) params,

  setup_data = function(data, params) data,

  # Combine data with defaults and set aesthetics from parameters
  use_defaults = function(self, data, params = list(), modifiers = aes(),
                          default_aes = NULL, theme = NULL, ...) {
    default_aes <- default_aes %||% self$default_aes

    # Inherit size as linewidth if no linewidth aesthetic and param exist
    if (self$rename_size && is.null(data$linewidth) && is.null(params$linewidth)) {
      data$linewidth <- data$size
      params$linewidth <- params$size
    }
    # Take care of subclasses setting the wrong default when inheriting from
    # a geom with rename_size = TRUE
    if (self$rename_size && is.null(default_aes$linewidth)) {
      deprecate_warn0("3.4.0", I("Using the `size` aesthetic in this geom"), I("`linewidth` in the `default_aes` field and elsewhere"))
      default_aes$linewidth <- default_aes$size
    }

    # Fill in missing aesthetics with their defaults
    missing_aes <- setdiff(names(default_aes), names(data))
    default_aes <- default_aes[missing_aes]
    themed_defaults <- eval_from_theme(default_aes, theme, class(self))
    default_aes[names(themed_defaults)] <- themed_defaults

    # Mark staged/scaled defaults as modifier (#6135)
    delayed <- is_scaled_aes(default_aes) | is_staged_aes(default_aes)
    if (any(delayed)) {
      modifiers <- defaults(modifiers, default_aes[delayed])
      default_aes <- default_aes[!delayed]
    }

    missing_eval <- lapply(default_aes, eval_tidy)
    # Needed for geoms with defaults set to NULL (e.g. GeomSf)
    missing_eval <- compact(missing_eval)

    if (empty(data)) {
      data <- as_gg_data_frame(missing_eval)
    } else {
      data[names(missing_eval)] <- missing_eval
    }

    themed <- is_themed_aes(modifiers)
    if (any(themed)) {
      themed <- eval_from_theme(modifiers[themed], theme)
      modifiers <- modifiers[setdiff(names(modifiers), names(themed))]
      data[names(themed)] <- themed
    }

    # If any after_scale mappings are detected they will be resolved here
    # This order means that they will have access to all default aesthetics
    if (length(modifiers) != 0) {
      modified_aes <- try_fetch(
        eval_aesthetics(
          substitute_aes(modifiers), data,
          mask = list(stage = stage_scaled)
        ),
        error = function(cnd) {
          cli::cli_warn("Unable to apply staged modifications.", parent = cnd)
          data_frame0()
        }
      )

      # Check that all output are valid data
      check_nondata_cols(
        modified_aes, modifiers,
        problem = "Aesthetic modifiers returned invalid values.",
        hint    = "Did you map the modifier in the wrong layer?"
      )

      modified_aes <- cleanup_mismatched_data(modified_aes, nrow(data), "after_scale")
      data[names(modified_aes)] <- modified_aes
    }

    # Override mappings with params
    aes_params <- intersect(self$aesthetics(), names(params))
    new_params <- params[aes_params]
    check_aesthetics(new_params, nrow(data))
    data[aes_params] <- new_params

    # Restore any AsIs classes (#5656)
    is_asis <- which(vapply(new_params, inherits, what = "AsIs", logical(1)))
    for (i in aes_params[is_asis]) {
      data[[i]] <- I(data[[i]])
    }
    data
  },

  # Most parameters for the geom are taken automatically from draw_panel() or
  # draw_groups(). However, some additional parameters may be needed
  # for setup_data() or handle_na(). These can not be imputed automatically,
  # so the slightly hacky "extra_params" field is used instead. By
  # default it contains `na.rm`
  extra_params = c("na.rm"),

  parameters = function(self, extra = FALSE) {
    # Look first in draw_panel. If it contains ... then look in draw groups
    panel_args <- names(ggproto_formals(self$draw_panel))
    group_args <- names(ggproto_formals(self$draw_group))
    args <- if ("..." %in% panel_args) group_args else panel_args

    # Remove arguments of defaults
    args <- setdiff(args, names(ggproto_formals(Geom$draw_group)))

    if (extra) {
      args <- union(args, self$extra_params)
    }
    args
  },

  aesthetics = function(self) {
    if (is.null(self$required_aes)) {
      required_aes <- NULL
    } else {
      required_aes <- unlist(strsplit(self$required_aes, '|', fixed = TRUE))
    }
    c(union(required_aes, names(self$default_aes)), self$optional_aes, "group")
  },

  # Should the geom rename size to linewidth?
  rename_size = FALSE

)

#' @export
#' @rdname is_tests
is_geom <- function(x) inherits(x, "Geom")

eval_from_theme <- function(aesthetics, theme, class = NULL) {
  themed <- is_themed_aes(aesthetics)
  if (!any(themed)) {
    return(aesthetics)
  }

  element <- calc_element("geom", theme) %||% .default_geom_element
  class <- setdiff(class, c("Geom", "ggproto", "gg"))

  if (length(class) > 0) {

    # CamelCase to dot.case
    class <- gsub("([A-Za-z])([A-Z])([a-z])", "\\1.\\2\\3", class)
    class <- gsub("([a-z])([A-Z])", "\\1.\\2", class)
    class <- to_lower_ascii(class)

    class <- class[class %in% names(theme)]

    # Inherit up to parent geom class
    if (length(class) > 0) {
      for (cls in rev(class)) {
        element <- combine_elements(theme[[cls]], element)
      }
    }
  }

  lapply(aesthetics[themed], eval_tidy, data = element)
}

#' Graphical units
#'
#' Multiply size in mm by these constants in order to convert to the units
#' that grid uses internally for `lwd` and `fontsize`.
#'
#' @name graphical-units
#' @keywords internal
#' @aliases NULL
NULL

#' @export
#' @rdname graphical-units
.pt <- 72.27 / 25.4
#' @export
#' @rdname graphical-units
.stroke <- 96 / 25.4

check_aesthetics <- function(x, n) {
  ns <- list_sizes(x)
  good <- ns == 1L | ns == n

  if (all(good)) {
    return()
  }

  cli::cli_abort(c(
    "Aesthetics must be either length 1 or the same as the data ({n}).",
    "x" = "Fix the following mappings: {.col {names(which(!good))}}."
  ))
}

fix_linewidth <- function(data, name) {
  if (is.null(data$linewidth) && !is.null(data$size)) {
    deprecate_warn0("3.4.0", I(paste0("Using the `size` aesthetic with ", name)), I("the `linewidth` aesthetic"))
    data$linewidth <- data$size
  }
  data
}