geom_abline2: Add an abline that does not exceed the extrema of the axes...
In vandenman/JASPgraphs: Custom Graphs for JASP

The default abline of ggplot2 will exceeds the breaks and goes from one set of limits to the next. This is a modified verions that respect one will not exceed the extrema of the x and y-breaks.

geom_abline2(
  mapping = NULL,
  data = NULL,
  method = c("breaks", "ggplot2"),
  ...,
  slope,
  intercept,
  na.rm = FALSE,
  show.legend = NA
)

`mapping`	Set of aesthetic mappings created by `aes()` or `aes_()`.
`data`	The data to be displayed in this layer. There are three options: If `NULL`, the default, the data is inherited from the plot data as specified in the call to `ggplot()`. A `data.frame`, or other object, will override the plot data. All objects will be fortified to produce a data frame. See `fortify()` for which variables will be created. A `function` will be called with a single argument, the plot data. The return value must be a `data.frame`, and will be used as the layer data. A `function` can be created from a `formula` (e.g. `~ head(.x, 10)`).
`method`	Either "breaks" (default) to respect the extrema of the axes or "ggplot2" to obtain the ggplot2 behavior.
`...`	Other arguments passed on to `layer()`. These are often aesthetics, used to set an aesthetic to a fixed value, like `colour = "red"` or `size = 3`. They may also be parameters to the paired geom/stat.
`slope`	Parameters that control the position of the line. If these are set, `data`, `mapping` and `show.legend` are overridden.
`intercept`	Parameters that control the position of the line. If these are set, `data`, `mapping` and `show.legend` are overridden.
`na.rm`	If `FALSE`, the default, missing values are removed with a warning. If `TRUE`, missing values are silently removed.
`show.legend`	logical. Should this layer be included in the legends? `NA`, the default, includes if any aesthetics are mapped. `FALSE` never includes, and `TRUE` always includes. It can also be a named logical vector to finely select the aesthetics to display.

library(ggplot2)
library(jaspGraphs)

dfRect <- data.frame(xmin = -10, ymin = -10, xmax = 10, ymax = 10)
basePlot <- ggplot(data = dfRect, aes(xmin = xmin, ymin = ymin, ymax = ymax, xmax = xmax)) +
  geom_rect(fill = NA, color = "black") +
  geom_rangeframe() +
  themeJaspRaw(legend.position = "right")

slopes <- seq(-5, 5, length.out = 15)
ints   <- seq(-2, 2, length.out = length(slopes))
basePlot +
  geom_abline2(intercept = ints - 2, slope = slopes, method = "breaks",  color = "green") +
  geom_abline2(intercept = ints + 2, slope = slopes, method = "ggplot2", color = "red") +
  ggtitle("specify 'method' manually")

dfAbline <- data.frame(
  intercept = -9:8,
  slope = 0.35,
  method = rep(c("ggplot2", "breaks"), 9)
)

basePlot +
  geom_abline2(data = dfAbline, mapping = aes(
    intercept = intercept, slope = slope, method = method, color = method
  ), show.legend = TRUE) +
  ggtitle("specify 'method' through aes")

basePlot + geom_abline2(data = dfAbline, mapping = aes(
    intercept = intercept, slope = slope, color = method
  )) +
  ggtitle("if method is not specified, 'breaks' is used as a default")