Automatically remove the tick length when tick is blank

[Yunuuuu]

In situations when we want to remove margins, we must set both ticks and ticks length to remove the width/heigth of axis in the underlying gtable. As user would expect the empty size when they remove the axis using element_blank().

Issue in stackoverflow: https://stackoverflow.com/questions/40407498/how-to-remove-margins-in-ggplot2-chart

Please note the 10th height which is the height of the axis grob.

library(ggplot2)
p1 <- ggplot(mtcars) +
  geom_point(aes(mpg, disp)) +
  theme(
    axis.title.x = element_blank(),
    axis.text.x = element_blank(),
    axis.ticks.x = element_blank(),
    plot.margin = margin()
  )
ggplotGrob(p1)$heights
#>  [1] 0points                                                                 
#>  [2] 0points                                                                 
#>  [3] 0cm                                                                     
#>  [4] 0cm                                                                     
#>  [5] 0cm                                                                     
#>  [6] 0points                                                                 
#>  [7] 0cm                                                                     
#>  [8] 0cm                                                                     
#>  [9] 1null                                                                   
#> [10] sum(0.0966514459665145cm, max(0points, -0.0966514459665145cm), 0cm, 0cm)
#> [11] 0cm                                                                     
#> [12] 0points                                                                 
#> [13] 0cm                                                                     
#> [14] 0cm                                                                     
#> [15] 0points                                                                 
#> [16] 0points

ggplotGrob(p1 +
  theme(axis.ticks.length = unit(0, "mm")))$heights
#>  [1] 0points                               0points                              
#>  [3] 0cm                                   0cm                                  
#>  [5] 0cm                                   0points                              
#>  [7] 0cm                                   0cm                                  
#>  [9] 1null                                 sum(0cm, max(0points, 0cm), 0cm, 0cm)
#> [11] 0cm                                   0points                              
#> [13] 0cm                                   0cm                                  
#> [15] 0points                               0points

^{Created on 2024-09-01 with reprex v2.1.0}