Consistent fill lighten for area types

[grantmcdermott]

Closes #646

Using the same summary that I shared in my earlier comment:

• Grouped barplot, boxplot, and violin now use the same lighter-but-opaque fill as their single-group counterparts. This fixes the the original inconsistency that you pointed out at the top of this issue (dark saturated bars vs. semi-transparent boxes).
  • The way that this works is that each of these types gains a lighten argument (default TRUE). So, for example, you could override with type_barplot(lighten = FALSE) to fall back to the old saturated palette colour.
  • spineplot also gets a similar lightening treatment, but only for the special y == by case. I've also made sure that these get consistent (black) borders regardless of grouping.
• The alpha-darkening bug is fixed. We now resolve the palette opaque, lighten, and then layer any transparency on top.s fixed.

MWE

Using some of the examples from the original issues:

pkgload::load_all("~/Documents/Projects/tinyplot/")
#> ℹ Loading tinyplot
tinytheme("clean2")
tinyplot(~ species, data = penguins)

tinyplot(~ species | island, data = penguins)

tinyplot(body_mass ~ species, data = penguins)

tinyplot(body_mass ~ species | sex, data = penguins)

tinyplot(~ species, data = penguins)

tinyplot(~ species, data = penguins, fill = 0.7)

^{Created on 2026-07-01 with reprex v2.1.1}

[zeileis]

To support specifications like lighten = 0.5 in addition to just lighten = TRUE we could use:

lighten_col = function(x, amount = 0.8) {
  x = to_hcl(x)
  hcl(
    h = x[, "H"],
    c = x[, "C"] * (1 - amount),
    l = 100 - (100 - x[, "L"]) * (1 - amount),
    alpha = attr(x, "alpha")
  )
}

By default this yields similar colors as the current lighten_fill() which is based on seq_palette(..., n = 3)[3]. Because we just need the lightened color here (rather than a palette going from the full color to the lightened one), lighten_col() can be a little bit simpler and hence leads to slightly different output.

Additionally, we may want to build in a catch that makes sure that lighten_col("black") returns "lightgray" to be exactly consistent with base R.

[grantmcdermott]

Thanks @zeileis, I think that both lighten = [0,1] and lighten_col are good ideas... But I'm afraid that I'm up against a hard deadline and so will have to defer to until a later date.

(tl;dr I'm leaving for 3 weeks vacation, with limited computer access. But I have to get this next CRAN submission out first, so that some work colleagues can easily use v0.7.0 for an internal project while I'm gone. It's a long story, but they need some our latest features and also have to install from the official CRAN distribution for some infosec reasons.)

Anyway, the bottom line is that I need to merge this today if it's going to make the v0.7.0 submission. IMHO it should be included if at all possible and I also feel it's basically in good enough shape now. But I can hold off until later today if you need/want to confirm anything else on your side.

Let me know!

[grantmcdermott]

P.S. I realize that I didn't include any spineplot MWEs above. I was probably unnecessarily confusing in my previous comment #646 (comment)... The takehome version is that, for most cases, spineplots are essentially unchanged. The only user-facing changes that I implemented were:

1. We now draw black borders by default for all spineplots; whereas we previously turned these off automagically for some plots. Note that users can still turn borders off manually, by calling (say) lty = 0. This feels more principled to me.

pkgload::load_all("~/Documents/Projects/tinyplot/")
#> ℹ Loading tinyplot
tinytheme("clean2")
tinyplot(
  Species ~ Sepal.Length, data = iris, 
  type = "spineplot"
)

tinyplot(
  Species ~ Sepal.Length, data = iris,
  type = "spineplot", lty = 0
)

2. Users have the option to call lighten = TRUE for spineplots where y==by (and only for this narrow case). This argument is set to FALSE by default, but I felt it made sense to add the option give our other updates to barplot and co. above (although the default for these other types is obviously TRUE).

tinyplot(
  Species ~ Sepal.Length | Species, data = iris,
  type = "spineplot"
)

tinyplot(
  Species ~ Sepal.Length | Species, data = iris,
  type = type_spineplot(lighten = TRUE)
)

[Copilot]

Pull request overview

This PR addresses #646 by making multi-group area-based plot types use consistent lighter-but-opaque fills (matching the single-group look), while introducing an explicit lighten toggle to opt out where appropriate (and keeping histogram/spineplot defaults aligned with their visual constraints).

Changes:

• Add lighten support to barplot, boxplot, and violin types (default TRUE) and update fill/alpha layering so numeric fill/alpha applies on top of the (optionally lightened) base fill.
• Add lighten support to spineplot (default FALSE, only meaningful for the y == by case) and adjust legend fill resolution for grouped spineplots.
• Update documentation, vignettes, tests, and snapshot artifacts to reflect the new defaults and options.

Reviewed changes

Copilot reviewed 22 out of 61 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
vignettes/gallery_figs/spineplot-titanic.R	Adjusts gallery figure params to match updated spineplot/legend styling.
vignettes/gallery_figs/likert.R	Uses type_barplot(lighten = FALSE, ...) to preserve intended saturated fills in the likert example.
vignettes/gallery_figs/barplot-meat.R	Demonstrates opting out of fill lightening for barplots in gallery output.
R/zzz.R	Adds lighten to the recognized argument set used across the package.
R/type_violin.R	Introduces lighten parameter plumbed into violin type data for consistent grouped fills.
R/type_spineplot.R	Adds lighten option for y == by spineplots and refines frame/legend behavior.
R/type_boxplot.R	Introduces lighten parameter for boxplots and routes it into type data.
R/type_barplot.R	Introduces lighten parameter for barplots and routes it into type data.
R/tinyplot.R	Adds a global settings$lighten default used by grouped-fill resolution.
R/legend.R	Ensures grouped spineplot legends mirror plotted fill behavior (including lightening).
NEWS.md	Documents the grouped-fill consistency change and new lighten options.
man/type_violin.Rd	Updates generated docs for new violin behavior/arguments.
man/type_spineplot.Rd	Updates generated docs for new spineplot behavior/arguments.
man/type_boxplot.Rd	Updates generated docs for new boxplot behavior/arguments.
man/type_barplot.Rd	Updates generated docs for new barplot behavior/arguments.
inst/tinytest/test-type_violin.R	Updates violin snapshot tests for new defaults and adds lighten = FALSE coverage.
inst/tinytest/test-type_spineplot.R	Updates spineplot snapshot tests and adds lighten = TRUE coverage for y == by.
inst/tinytest/test-type_boxplot.R	Adds snapshot coverage for type_boxplot(lighten = FALSE).
inst/tinytest/test-type_barplot.R	Updates barplot snapshot tests for new defaults and adds lighten = FALSE coverage.
inst/tinytest/test-tinyplot_add.R	Updates jitter-layer snapshots impacted by new fill/alpha behavior.
inst/tinytest/_tinysnapshot/spineplot_yby.svg	Snapshot update reflecting spineplot legend/frame styling changes.
inst/tinytest/_tinysnapshot/spineplot_yby_lighten_true.svg	New snapshot for spineplot with lighten = TRUE in the y == by case.
inst/tinytest/_tinysnapshot/spineplot_yby_lighten_false.svg	New snapshot for spineplot with lighten = FALSE in the y == by case.
inst/tinytest/_tinysnapshot/spineplot_xby.svg	Snapshot update reflecting spineplot legend/frame styling changes.
inst/tinytest/_tinysnapshot/spineplot_facet_by.svg	Snapshot update reflecting spineplot legend/frame styling changes.
inst/tinytest/_tinysnapshot/boxplot_groups.svg	Snapshot update for new grouped boxplot fill behavior.
inst/tinytest/_tinysnapshot/boxplot_groups_x_same.svg	Snapshot update for new grouped boxplot fill behavior.
inst/tinytest/_tinysnapshot/boxplot_groups_x_same_legendFALSE.svg	Snapshot update for new grouped boxplot fill behavior without legend.
inst/tinytest/_tinysnapshot/boxplot_groups_x_equivalent.svg	Snapshot update for new grouped boxplot fill behavior.
inst/tinytest/_tinysnapshot/boxplot_groups_x_equivalent_legendFALSE.svg	Snapshot update for new grouped boxplot fill behavior without legend.
inst/tinytest/_tinysnapshot/boxplot_groups_lighten_false.svg	New snapshot for grouped boxplot with lighten = FALSE.
inst/tinytest/_tinysnapshot/boxplot_groups_facets_with_missings.svg	Snapshot update for new grouped boxplot fill behavior with facets/missings.
inst/tinytest/_tinysnapshot/boxplot_groups_argpass.svg	Snapshot update for grouped boxplot argument-passing case under new fill behavior.
inst/tinytest/_tinysnapshot/boxplot_facet_by_x_same.svg	Snapshot update for faceted grouped boxplot under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_offset_stacked.svg	Snapshot update for barplot offset example under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_offset_beside_group.svg	Snapshot update for barplot offset/beside grouped example under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_group.svg	Snapshot update for grouped barplot under new default lightened fills.
inst/tinytest/_tinysnapshot/barplot_group_lighten_false.svg	New snapshot for grouped barplot with lighten = FALSE.
inst/tinytest/_tinysnapshot/barplot_group_beside.svg	Snapshot update for grouped barplot (beside) under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_flip_fancy.svg	Snapshot update for flipped “fancy” barplot under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_facet.svg	Snapshot update for faceted barplot under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_facet_free.svg	Snapshot update for faceted free-scale barplot under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_custom_ytitle.svg	Snapshot update for custom-title barplot under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_custom_xtitle.svg	Snapshot update for custom-title barplot under new fill behavior.
inst/tinytest/_tinysnapshot/barplot_aggregation.svg	Snapshot update for aggregated barplot under new fill behavior.
altdoc/pkgdown.yml	Updates pkgdown build timestamp metadata.

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