ggtitle height varies with descending letters

[WHMan]

Hi there,

I just noticed that the height of a ggplot2 main title depends on the letters used. Although there is no difference in the title height (and therefore the dimensions of the plot itself) between titles with only typical sized letter (e.g. "arrr") or with ascenders (e.g. "brrr"), the title height increases with the inclusion of descenders (e.g. "prrr"). Although I understand that as a workaround I can use all-caps or readjust the plot height with ggplotGrob, I wonder whether I missed a parameter (within theme?) that could fixate the title height independent on the letters used.

library(ggplot2)
library(gridExtra)
grid.arrange(ggplot() + ggtitle("arrr"),
             ggplot() + ggtitle("brrr"),
             ggplot() + ggtitle("prrr"),
             nrow = 1)

Thanks in advance!

[hadley]

There isn't unfortunately 😞

[clauswilke]

I've run into this problem also and I debugged it in quite some detail. I'm writing up my findings here in the hope they may be useful to somebody. I don't have the time right now to prepare a proper pull request but may be able to do so in the future.

The problem is caused by this line:

ggplot2/R/margins.R

Line 73 in bef2f38

descent <- descentDetails(text_grob)

The function descentDetails() returns different values depending on the text grob it is run on:

> descentDetails(textGrob("a"))
[1] 0.001953125inches
> descentDetails(textGrob("g"))
[1] 0.0350748697916667inches

A simple fix would be to replace the string in the text grob with a constant string that is always used. This should return the same descent height at all times, only dependent on font metrics and independent on the specific label used. So, we could replace this line:

descent <- descentDetails(text_grob)

with these two lines:

temp <- editGrob(text_grob, label = "gjpqyQ")
descent <- descentDetails(temp)

to get consistent descent values regardless of the text label shown in the plot.

[clauswilke]

Here's the effect of this proposed patch.

Example 1:

library(ggplot2)
library(gridExtra)
grid.arrange(ggplot() + ggtitle("arrr"),
             ggplot() + ggtitle("grrr"),
             nrow = 1)

Current ggplot2:

With patch:

Example 2:

p <- ggplot(iris, aes(Sepal.Length, Sepal.Width, color = Species)) + geom_point()
grid.arrange(p + ggtitle("arrr") + scale_color_discrete(name = "abcd"),
             p + ggtitle("grrr"),
             nrow = 1)

Current ggplot2:

With patch:

Note that this also fixes the layout of the legend title.

[lock]

This old issue has been automatically locked. If you believe you have found a related problem, please file a new issue (with reprex) and link to this issue. https://reprex.tidyverse.org/