R/plot-build.R

In ggtern: An Extension to 'ggplot2', for the Creation of Ternary Diagrams

#' Build ggplot for rendering (ggtern version).
#'
#' \code{ggplot_build} takes the plot object, and performs all steps necessary
#' to produce an object that can be rendered.  This function outputs two pieces:
#' a list of data frames (one for each layer), and a panel object, which
#' contain all information about axis limits, breaks etc.
#'
#' \code{layer_data}, \code{layer_grob}, and \code{layer_scales} are helper
#' functions that returns the data, grob, or scales associated with a given
#' layer. These are useful for tests.
#'
#' @param plot ggplot object
#' @seealso \code{\link{print.ggplot}} and \code{\link{benchplot}} for
#'  functions that contain the complete set of steps for generating
#'  a ggplot2 plot.
#' @keywords internal
#' @author Nicholas Hamilton
#' @rdname ggplot_build
#' @export
ggplot_build <- function(plot) {
  UseMethod('ggplot_build')
}

#' @export
ggplot_build.ggplot <- function(plot) {
  plot <- ggint$plot_clone(plot)
  if (length(plot$layers) == 0) {
    plot <- plot + geom_blank()
  }
  
  #NH Check the plot is a teryary plot
  isTernary = inherits(plot$coordinates,'CoordTern') ##NH
  if(isTernary){
    plot$layers <- strip_unapproved(plot$layers) ##NH
    plot <- layers_add_or_remove_mask(plot) #NH
  }
  
  #Check the Layers
  layers <- plot$layers
  layer_data <- lapply(layers, function(y) y$layer_data(plot$data))
  
  scales <- plot$scales
  # Apply function to layer and matching data
  by_layer <- function(f) {
    out <- vector("list", length(data))
    for (i in seq_along(data)) {
      out[[i]] <- f(l = layers[[i]], d = data[[i]])
    }
    out
  }
  
  # Allow all layers to make any final adjustments based
  # on raw input data and plot info
  data <- layer_data
  data <- by_layer(function(l, d) l$setup_layer(d, plot))
  
  # Initialise panels, add extra data for margins & missing facetting
  # variables, and add on a PANEL variable to data
  layout <- ggint$create_layout(plot$facet,plot$coordinates)
  data   <- layout$setup(data, plot$data, plot$plot_env)
  
  # Compute aesthetics to produce data with generalised variable names
  data <- by_layer(function(l, d) l$compute_aesthetics(d, plot))
  
  # Transform all scales
  data <- lapply(data, ggint$scales_transform_df, scales = scales) ##NH
  
  # Map and train positions so that statistics have access to ranges
  # and all positions are numeric
  scale_x <- function() scales$get_scales("x")
  scale_y <- function() scales$get_scales("y")
  
  layout$train_position(data, scale_x(), scale_y())
  data  <- layout$map_position(data)
  
  # Apply and map statistics
  data <- by_layer(function(l, d) l$compute_statistic(d, layout))
  data <- by_layer(function(l, d) l$map_statistic(d, plot))
  
  # Make sure missing (but required) aesthetics are added
  ggint$scales_add_missing(plot, c("x", "y"), plot$plot_env)
  
  # Make sure missing (but required) ternary aesthetics are added, and ensure the limits are common
  if(isTernary) 
    plot = scales_add_missing_tern(plot)
  
  # Reparameterise geoms from (e.g.) y and width to ymin and ymax
  data <- by_layer(function(l, d) l$compute_geom_1(d))
  
  # Apply position adjustments
  data <- by_layer(function(l, d) l$compute_position(d, layout))
  
  # Reset position scales, then re-train and map.  This ensures that facets
  # have control over the range of a plot: is it generated from what's
  # displayed, or does it include the range of underlying data
  layout$reset_scales()
  layout$train_position(data, scale_x(), scale_y())
  layout$setup_panel_params()
  data <- layout$map_position(data)
  
  # Train and map non-position scales
  npscales <- scales$non_position_scales()
  if (npscales$n() > 0) {
    lapply(data, ggint$scales_train_df, scales = npscales)       ##NH
    data <- lapply(data, ggint$scales_map_df, scales = npscales) ##NH
  }
  
  # Fill in defaults etc.
  data <- by_layer(function(l, d) l$compute_geom_2(d))
  
  # Let layer stat have a final say before rendering
  data <- by_layer(function(l, d) l$finish_statistics(d))
  
  # Let Layout modify data before rendering
  data <- layout$finish_data(data)
  
  structure(
    list(data = data, layout = layout, plot = plot),
    class = "ggplot_built"
  )
}

#' @rdname ggplot_build
#' @export
layer_data <- function(plot, i = 1L) {
  ggplot_build(plot)$data[[i]]
}

# @export
# @rdname ggplot_build
#layer_scales <- function(plot, i = 1L, j = 1L) {
#  b <- ggplot_build(plot)
#  
#  layout <- b$panel$layout
#  selected <- layout[layout$ROW == i & layout$COL == j, , drop = FALSE]
#  
#  list(
#    x = b$panel$x_scales[[selected$SCALE_X]],
#    y = b$panel$y_scales[[selected$SCALE_Y]]
#  )
#}

# @export
# @rdname ggplot_build
#layer_grob <- function(plot, i = 1L) {
#  b <- ggplot_build(plot)
#  b$plot$layers[[i]]$draw_geom(b$data[[i]], b$panel, b$plot$coordinates)
#}

#' Build a plot with all the usual bits and pieces.
#'
#' This function builds all grobs necessary for displaying the plot, and
#' stores them in a special data structure called a \code{\link{gtable}}.
#' This object is amenable to programmatic manipulation, should you want
#' to (e.g.) make the legend box 2 cm wide, or combine multiple plots into
#' a single display, preserving aspect ratios across the plots.
#'
#' @seealso \code{\link{print.ggplot}} and \code{link{benchplot}} for
#'  for functions that contain the complete set of steps for generating
#'  a ggplot2 plot.
#' @return a \code{\link{gtable}} object
#' @keywords internal
#' @param plot plot object
#' @param data plot data generated by \code{\link{ggplot_build}}
#' @rdname ggplot_gtable
#' @export
ggplot_gtable <- function(data) {
  UseMethod('ggplot_gtable')
}

#' @export
ggplot_gtable.ggplot_built <- function(data) {
  plot <- data$plot
  layout <- data$layout
  data <- data$data
  theme <- ggint$plot_theme(plot) #NH
  
  # Is the current plot a ternary plot
  isTernary  <- inherits(plot$coordinates,'CoordTern') ##NH
  
  geom_grobs <- Map(function(l, d) l$draw_geom(d, layout), plot$layers, data)
  if(!isTernary) ## NH This is in the base ggplot code, but causes error for ggtern
    layout$setup_panel_guides(plot$guides, plot$layers, plot$mapping) ## NH 21st Jul 2021
  plot_table <- layout$render(geom_grobs, data, theme, plot$labels)
  
  #NH For Ternary Plot.
  if(isTernary){
    latex      <- calc_element('tern.plot.latex', theme, verbose = FALSE)
    plot$labels<- lapply(plot$labels,function(x) label_formatter(x,latex = latex))
    plot_table <- plot$coordinates$remove_labels(plot_table)
  }
  
  # Legends
  position <- theme$legend.position %||% "right"
  if (length(position) == 2) {
    position <- "manual"
  }
  
  legend_box <- if (position != "none") {
    ggint$build_guides(plot$scales, plot$layers, plot$mapping, position, theme, plot$guides, plot$labels) ##NH
  } else {
    zeroGrob()
  }
  
  if (ggint$is.zero(legend_box)) { ##NH
    position <- "none"
  } else {
    # these are a bad hack, since it modifies the contents of viewpoint directly...
    legend_width  <- gtable_width(legend_box)
    legend_height <- gtable_height(legend_box)
    
    # Set the justification of the legend box
    # First value is xjust, second value is yjust
    just <- valid.just(theme$legend.justification)
    xjust <- just[1]
    yjust <- just[2]
    
    if (position == "manual") {
      xpos <- theme$legend.position[1]
      ypos <- theme$legend.position[2]
      
      # x and y are specified via theme$legend.position (i.e., coords)
      legend_box <- editGrob(legend_box,
        vp = viewport(x = xpos, y = ypos, just = c(xjust, yjust),
          height = legend_height, width = legend_width))
    } else {
      # x and y are adjusted using justification of legend box (i.e., theme$legend.justification)
      legend_box <- editGrob(legend_box,
        vp = viewport(x = xjust, y = yjust, just = c(xjust, yjust)))
      legend_box <- gtable_add_rows(legend_box, unit(yjust, 'null'))
      legend_box <- gtable_add_rows(legend_box, unit(1 - yjust, 'null'), 0)
      legend_box <- gtable_add_cols(legend_box, unit(xjust, 'null'), 0)
      legend_box <- gtable_add_cols(legend_box, unit(1 - xjust, 'null'))
    }
  }
  
  panel_dim <- find_panel(plot_table)
  # for align-to-device, use this:
  # panel_dim <-  summarise(plot_table$layout, t = min(t), r = max(r), b = max(b), l = min(l))
  
  theme$legend.box.spacing <- theme$legend.box.spacing %||% unit(0.2, 'cm')
  if (position == "left") {
    plot_table <- gtable_add_cols(plot_table, theme$legend.box.spacing, pos = 0)
    plot_table <- gtable_add_cols(plot_table, legend_width, pos = 0)
    plot_table <- gtable_add_grob(plot_table, legend_box, clip = "off",
      t = panel_dim$t, b = panel_dim$b, l = 1, r = 1, name = "guide-box")
  } else if (position == "right") {
    plot_table <- gtable_add_cols(plot_table, theme$legend.box.spacing, pos = -1)
    plot_table <- gtable_add_cols(plot_table, legend_width, pos = -1)
    plot_table <- gtable_add_grob(plot_table, legend_box, clip = "off",
      t = panel_dim$t, b = panel_dim$b, l = -1, r = -1, name = "guide-box")
  } else if (position == "bottom") {
    plot_table <- gtable_add_rows(plot_table, theme$legend.box.spacing, pos = -1)
    plot_table <- gtable_add_rows(plot_table, legend_height, pos = -1)
    plot_table <- gtable_add_grob(plot_table, legend_box, clip = "off",
      t = -1, b = -1, l = panel_dim$l, r = panel_dim$r, name = "guide-box")
  } else if (position == "top") {
    plot_table <- gtable_add_rows(plot_table, theme$legend.box.spacing, pos = 0)
    plot_table <- gtable_add_rows(plot_table, legend_height, pos = 0)
    plot_table <- gtable_add_grob(plot_table, legend_box, clip = "off",
      t = 1, b = 1, l = panel_dim$l, r = panel_dim$r, name = "guide-box")
  } else if (position == "manual") {
    # should guide box expand whole region or region without margin?
    plot_table <- gtable_add_grob(plot_table, legend_box,
      t = panel_dim$t, b = panel_dim$b, l = panel_dim$l, r = panel_dim$r,
      clip = "off", name = "guide-box")
  }
  
  # Title
  title <- element_render(theme, "plot.title", plot$labels$title, margin_y = TRUE)
  title_height <- grobHeight(title)
  
  # Subtitle
  subtitle <- element_render(theme, "plot.subtitle", plot$labels$subtitle, margin_y = TRUE)
  subtitle_height <- grobHeight(subtitle)
  
  # Tag
  tag <- element_render(theme, "plot.tag", plot$labels$tag, margin_y = TRUE, margin_x = TRUE)
  tag_height <- grobHeight(tag)
  tag_width <- grobWidth(tag)
  
  # whole plot annotation
  caption <- element_render(theme, "plot.caption", plot$labels$caption, expand_y = TRUE)
  caption_height <- grobHeight(caption)
  
  pans <- plot_table$layout[grepl("^panel", plot_table$layout$name), ,
    drop = FALSE]
  
  plot_table <- gtable_add_rows(plot_table, subtitle_height, pos = 0)
  plot_table <- gtable_add_grob(plot_table, subtitle, name = "subtitle",
    t = 1, b = 1, l = min(pans$l), r = max(pans$r), clip = "off")
  
  plot_table <- gtable_add_rows(plot_table, title_height, pos = 0)
  plot_table <- gtable_add_grob(plot_table, title, name = "title",
    t = 1, b = 1, l = min(pans$l), r = max(pans$r), clip = "off")
  
  plot_table <- gtable_add_rows(plot_table, caption_height, pos = -1)
  plot_table <- gtable_add_grob(plot_table, caption, name = "caption",
    t = -1, b = -1, l = min(pans$l), r = max(pans$r), clip = "off")
  
  plot_table <- gtable_add_rows(plot_table, unit(0, 'pt'), pos = 0)
  plot_table <- gtable_add_cols(plot_table, unit(0, 'pt'), pos = 0)
  plot_table <- gtable_add_rows(plot_table, unit(0, 'pt'), pos = -1)
  plot_table <- gtable_add_cols(plot_table, unit(0, 'pt'), pos = -1)
  
  tag_pos <- theme$plot.tag.position %||% "topleft"
  if (length(tag_pos) == 2) tag_pos <- "manual"
  valid_pos <- c("topleft", "top", "topright", "left", "right", "bottomleft",
                 "bottom", "bottomright")
  
  if (!(tag_pos == "manual" || tag_pos %in% valid_pos)) {
    stop("plot.tag.position should be a coordinate or one of ",
         paste(valid_pos, collapse = ', '), call. = FALSE)
  }
  
  if (tag_pos == "manual") {
    xpos <- theme$plot.tag.position[1]
    ypos <- theme$plot.tag.position[2]
    tag_parent <- ggint$justify_grobs(tag, x = xpos, y = ypos,
                                hjust = theme$plot.tag$hjust,
                                vjust = theme$plot.tag$vjust,
                                int_angle = theme$plot.tag$angle,
                                debug = theme$plot.tag$debug)
    plot_table <- gtable_add_grob(plot_table, tag_parent, name = "tag", t = 1,
                                  b = nrow(plot_table), l = 1,
                                  r = ncol(plot_table), clip = "off")
  } else {
    # Widths and heights are reassembled below instead of assigning into them
    # in order to avoid bug in grid 3.2 and below.
    if (tag_pos == "topleft") {
      plot_table$widths <- unit.c(tag_width, plot_table$widths[-1])
      plot_table$heights <- unit.c(tag_height, plot_table$heights[-1])
      plot_table <- gtable_add_grob(plot_table, tag, name = "tag",
                                    t = 1, l = 1, clip = "off")
    } else if (tag_pos == "top") {
      plot_table$heights <- unit.c(tag_height, plot_table$heights[-1])
      plot_table <- gtable_add_grob(plot_table, tag, name = "tag",
                                    t = 1, l = 1, r = ncol(plot_table),
                                    clip = "off")
    } else if (tag_pos == "topright") {
      plot_table$widths <- unit.c(plot_table$widths[-ncol(plot_table)], tag_width)
      plot_table$heights <- unit.c(tag_height, plot_table$heights[-1])
      plot_table <- gtable_add_grob(plot_table, tag, name = "tag",
                                    t = 1, l = ncol(plot_table), clip = "off")
    } else if (tag_pos == "left") {
      plot_table$widths <- unit.c(tag_width, plot_table$widths[-1])
      plot_table <- gtable_add_grob(plot_table, tag, name = "tag",
                                    t = 1, b = nrow(plot_table), l = 1,
                                    clip = "off")
    } else if (tag_pos == "right") {
      plot_table$widths <- unit.c(plot_table$widths[-ncol(plot_table)], tag_width)
      plot_table <- gtable_add_grob(plot_table, tag, name = "tag",
                                    t = 1, b = nrow(plot_table), l = ncol(plot_table),
                                    clip = "off")
    } else if (tag_pos == "bottomleft") {
      plot_table$widths <- unit.c(tag_width, plot_table$widths[-1])
      plot_table$heights <- unit.c(plot_table$heights[-nrow(plot_table)], tag_height)
      plot_table <- gtable_add_grob(plot_table, tag, name = "tag",
                                    t = nrow(plot_table), l = 1, clip = "off")
    } else if (tag_pos == "bottom") {
      plot_table$heights <- unit.c(plot_table$heights[-nrow(plot_table)], tag_height)
      plot_table <- gtable_add_grob(plot_table, tag, name = "tag",
                                    t = nrow(plot_table), l = 1, r = ncol(plot_table), clip = "off")
    } else if (tag_pos == "bottomright") {
      plot_table$widths <- unit.c(plot_table$widths[-ncol(plot_table)], tag_width)
      plot_table$heights <- unit.c(plot_table$heights[-nrow(plot_table)], tag_height)
      plot_table <- gtable_add_grob(plot_table, tag, name = "tag",
                                    t = nrow(plot_table), l = ncol(plot_table), clip = "off")
    }
  }
  
  # Margins
  plot_table <- gtable_add_rows(plot_table, theme$plot.margin[1], pos = 0)
  plot_table <- gtable_add_cols(plot_table, theme$plot.margin[2])
  plot_table <- gtable_add_rows(plot_table, theme$plot.margin[3])
  plot_table <- gtable_add_cols(plot_table, theme$plot.margin[4], pos = 0)
  
  if (inherits(theme$plot.background, "element")) {
    plot_table <- gtable_add_grob(plot_table,
      element_render(theme, "plot.background"),
      t = 1, l = 1, b = -1, r = -1, name = "background", z = -Inf)
    plot_table$layout <- plot_table$layout[c(nrow(plot_table$layout), 1:(nrow(plot_table$layout) - 1)),]
    plot_table$grobs <- plot_table$grobs[c(nrow(plot_table$layout), 1:(nrow(plot_table$layout) - 1))]
  }
  plot_table
}

#' Generate a ggplot2 plot grob (ggtern version)
#'
#' @param x ggplot2 object
#' @rdname ggplot_gtable
#' @export
ggplotGrob <- function(x) {
  ggplot_gtable(ggplot_build(x))
}