Faint lines through colour steps guide segments when `even.steps = FALSE`

[jimjam-slam]

This reprex actually comes from the current ggplot2 3.4.4 docs for guide_colorsteps, where it is visible:

df <- expand.grid(X1 = 1:10, X2 = 1:10)
df$value <- df$X1 * df$X2

  p <- ggplot(df, aes(X1, X2)) + geom_tile(aes(fill = value))

# By default each bin in the guide is the same size irrespectively of how
# their sizes relate in data space
p + scale_fill_binned(breaks = c(10, 25, 50))

# This can be changed with the `even.steps` argument
p + scale_fill_binned(
  breaks = c(10, 25, 50),
  guide = guide_coloursteps(even.steps = FALSE))

When I run this code on ggplot 3.4.4, I can't see the faint lines at low-resolution outputs, but if I run, ggsave at, say, width = 1920, height = 1080, units = 'px', or with SVG output, they're definitely visible. Mapping colour to the same variable as fill hides the lines from the tiles themselves but not from the colour bar (unless there's a way to merge the fill and colour guides rather than hiding one?).

[teunbrand]

The lines in the coloursteps guide (and rectangles in the main panel) appear to be anti-aliasing artifacts from drawing the guide as a series of small rectangles. Anti-aliasing settings depends on the device, so there isn't a lot ggplot2 can do on that front.

However, I don't see why guide_coloursteps() couldn't just draw a single rectangle between limits/breaks, so I'm going to consider this issue a feature request for an option like this.