Use gridtext (when available) to enable more complex text styling throughout ggplot2

[hadley]

• geom_label() can't rotate text & gets descent heights wrong #2785: Improved support for rotation, and better descent calculation
• Use markdown for italic/bold in titles #2743: Allow italic/bold in titles

[clauswilke]

The gridtext library will provide support for basic markdown/html rendering in the grid graphics framework. At a minimum, support will include bold, italics, super and subscripts, changing fonts and styling (color, size, etc.), and enclosing boxes with margin and padding. Proof-of-concept code exists and is already somewhat useful. Example follows.

library(ggplot2)
library(gridtext) # remotes::install_github("clauswilke/gridtext")

ggplot2 helper code

library(grid)
library(rlang)

# define new theme element that inherits from `element_text()`
element_markdown <- function(family = NULL, face = NULL, colour = NULL, size = NULL,
                             hjust = NULL, vjust = NULL, angle = NULL, lineheight = NULL,
                             color = NULL, margin = NULL,
                             debug = FALSE, inherit.blank = FALSE) {
  if (!is.null(color))
    colour <- color
  structure(
    list(
      family = family, face = face, colour = colour,
      size = size, hjust = hjust, vjust = vjust, angle = angle,
      lineheight = lineheight, margin = margin, debug = debug,
      inherit.blank = inherit.blank),
    class = c("element_markdown", "element_text", "element")
  )
}

# rendering of the theme element is handled by `labels_grob()`
element_grob.element_markdown <- function(element, label = "", x = NULL, y = NULL,
                                          family = NULL, face = NULL, colour = NULL, size = NULL,
                                          hjust = NULL, vjust = NULL, angle = NULL, lineheight = NULL,
                                          margin = NULL, margin_x = FALSE, margin_y = FALSE, ...) {
  if (is.null(label))
    return(ggplot2:::zeroGrob())
  
  vj <- vjust %||% element$vjust
  hj <- hjust %||% element$hjust
  margin <- margin %||% element$margin %||% ggplot2::margin(0, 0, 0, 0)
  angle <- angle %||% element$angle %||% 0
  
  x <- x %||% hj
  if (!is.unit(x))
    x <- unit(x, "npc")
  y <- y %||% vj
  if (!is.unit(y))
    y <- unit(y, "npc")
  
  markdown_grob(label, x = x, y = y, hjust = hj, vjust = vj, angle = angle,
                padding = margin, debug = element$debug)
}

ggplot(iris, aes(Sepal.Length, Sepal.Width, color = Species)) +
  geom_point(show.legend=TRUE, alpha = 0.5) +
  scale_color_manual(
    values = c("#0072B2", "#E69F00", "#009E73"),
    guide = "none"
  ) +
  labs(
    title = "Sepal **lengths** and **widths** of *Iris* species",
    subtitle = "<i><span style='color:#0072B2'>I.
setosa</span></i> | <i><span style='color:#E69F00'>I. versicolor</span></i> |
<i><span style='color:#009E73'>I. virginica</span></i>",
    x = "Sepal **length** (cm)", y = "Sepal **width** (cm)"
  ) +
  theme_minimal() +
  theme(
    plot.title = element_markdown(margin = ggplot2::margin(5, 0, 5, 0)),
    plot.subtitle = element_markdown(),
    axis.title.x = element_markdown(),
    axis.title.y = element_markdown(vjust = 0.5, hjust = 0.5, margin = margin(b = 5.5))
  )

^{Created on 2019-06-26 by the reprex package (v0.3.0)}

[paleolimbot]

This is so cool!

[alsmnn]

This sounds really awesome!
Will it be possible two add two line statements with superscripts in each line?

[aguerodev]

library(ggplot2)
library(gridtext) # remotes::install_github("clauswilke/gridtext")
library(grid)
library(rlang)

# define new theme element that inherits from `element_text()`
element_markdown <- function(family = NULL, face = NULL, colour = NULL, size = NULL,
                             hjust = NULL, vjust = NULL, angle = NULL, lineheight = NULL,
                             color = NULL, margin = NULL,
                             debug = FALSE, inherit.blank = FALSE) {
  if (!is.null(color))
    colour <- color
  structure(
    list(
      family = family, face = face, colour = colour,
      size = size, hjust = hjust, vjust = vjust, angle = angle,
      lineheight = lineheight, margin = margin, debug = debug,
      inherit.blank = inherit.blank),
    class = c("element_markdown", "element_text", "element")
  )
}

# rendering of the theme element is handled by `labels_grob()`
element_grob.element_markdown <- function(element, label = "", x = NULL, y = NULL,
                                          family = NULL, face = NULL, colour = NULL, size = NULL,
                                          hjust = NULL, vjust = NULL, angle = NULL, lineheight = NULL,
                                          margin = NULL, margin_x = FALSE, margin_y = FALSE, ...) {
  if (is.null(label))
    return(ggplot2:::zeroGrob())
  
  vj <- vjust %||% element$vjust
  hj <- hjust %||% element$hjust
  margin <- margin %||% element$margin %||% ggplot2::margin(0, 0, 0, 0)
  angle <- angle %||% element$angle %||% 0
  
  x <- x %||% hj
  if (!is.unit(x))
    x <- unit(x, "npc")
  y <- y %||% vj
  if (!is.unit(y))
    y <- unit(y, "npc")
  
  markdown_grob(label, x = x, y = y, hjust = hj, vjust = vj, angle = angle,
                padding = margin, debug = element$debug)
}

ggplot(iris, aes(Sepal.Length, Sepal.Width, color = Species)) +
  geom_point(show.legend=TRUE, alpha = 0.5) +
  scale_color_manual(
    values = c("#0072B2", "#E69F00", "#009E73"),
    guide = "none"
  ) +
  labs(
    title = "Sepal **lengths** and **widths** of *Iris* species",
    subtitle = "<i><span style='color:#0072B2'>I.
setosa</span></i> | <i><span style='color:#E69F00'>I. versicolor</span></i> |
<i><span style='color:#009E73'>I. virginica</span></i>",
    x = "Sepal **length** (cm)", y = "Sepal **width** (cm)"
  ) +
  theme_minimal() +
  theme(
    plot.title = element_markdown(margin = ggplot2::margin(5, 0, 5, 0)),
    plot.subtitle = element_markdown(),
    axis.title.x = element_markdown(),
    axis.title.y = element_markdown(vjust = 0.5, hjust = 0.5, margin = margin(b = 5.5))
  )
#> Error in markdown_grob(label, x = x, y = y, hjust = hj, vjust = vj, angle = angle, : could not find function "markdown_grob"

^{Created on 2020-02-02 by the reprex package (v0.3.0)}

[clauswilke]

@aguerodev Not sure what your point is. gridtext is now on CRAN and you'll have to use the published and documented API. https://wilkelab.org/gridtext/

[teunbrand]

I think ggtext and gridtext work well as a package and unless there are any requests for further integration, I'll close this issue.