Place the extreme ticks at the edge of the legend frame without extra padding

[caijun]

The following example is to illustrate my obsessive feature request. As you see, there is a small amount of padding between the first (or the last) legend tick and legend frame. How could I remove those paddings and make the first or the last legend ticks at the edge of legend frame?
Is there also an expand parameter available for colorbar scales?

---

Brief description of the problem

library(ggplot2)
p <- ggplot(mtcars, aes(hp, disp, color = mpg)) + 
  geom_point() + 
  scale_color_continuous(limits = c(10, 35),
                         breaks = seq(10, 35, by = 5),
                         guide = guide_colorbar(
                           direction = "horizontal",
                           title.position = "top", 
                           title.hjust = 0.5, 
                           ticks.colour = "white", 
                           frame.colour = "black", 
                           barwidth = 12)) + 
  theme(legend.position = "top")
p

^{Created on 2019-06-01 by the reprex package (v0.3.0)}

[clauswilke]

Set the nbin parameter to a large value (e.g., nbin = 1000). Maybe this should be added to the documentation.

library(ggplot2)
p <- ggplot(mtcars, aes(hp, disp, color = mpg)) + 
  geom_point() + 
  scale_color_continuous(
    limits = c(10, 35),
    breaks = seq(10, 35, by = 5),
    guide = guide_colorbar(
      direction = "horizontal",
      title.position = "top", 
      title.hjust = 0.5, 
      ticks.colour = "white", 
      frame.colour = "black", 
      barwidth = 12,
      nbin = 1000
    )
  ) + 
  theme(legend.position = "top")
p

^{Created on 2019-05-31 by the reprex package (v0.2.1)}

[caijun]

This is exactly what I am looking for. Thank you very much. Before creating this issue, I have searched on the internet for several hours. I totally agree with you that some examples should be added to illustrate the function of nbin parameter in the documentation.

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