feat: add make_mark and make_theme factory functions

- make_mark: registers custom S7 mark from any ggplot2 geom
- make_theme: creates reusable theme preset functions
- New file R/factory.R with full roxygen2 docs
- Added factory.R to DESCRIPTION Collate
- Tests: create custom mark, non-mark_ name warning, custom theme, custom base theme
- 383 pass, 0 fail

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: zorrooz

DESCRIPTION

@@ -26,7 +26,7 @@ Imports:
     S7 (>= 0.1.0),
     cli,
     patchwork
-Collate: 
+Collate:
     'class.R'
     'utils.R'
     'style.R'
@@ -35,6 +35,7 @@ Collate:
     'compose.R'
     'encode.R'
     'mark.R'
+    'factory.R'
     'plot.R'
     'project.R'
     'scale.R'

NAMESPACE

@@ -15,6 +15,8 @@ export(label_caption)
 export(label_legend)
 export(label_subtitle)
 export(label_title)
+export(make_mark)
+export(make_theme)
 export(mark_area)
 export(mark_bar)
 export(mark_boxplot)

R/factory.R

@@ -0,0 +1,82 @@
+#' @include class.R mark.R
+NULL
+
+# ---- make_mark ----
+#' Create a custom mark
+#'
+#' Registers a new S7 generic + method from any ggplot2 geom function,
+#' making it available in the plotit pipeline. The new mark behaves
+#' identically to built-in marks: it supports `mapping`, `data`,
+#' `position`, auto-dodge, and rasterization.
+#'
+#' @param name Mark name as a string (e.g. `"mark_spoke"`).
+#'   Should start with `"mark_"`.
+#' @param geom_fun A ggplot2 geom function
+#'   (e.g. `ggplot2::geom_spoke`).
+#' @return Invisibly returns the registered S7 generic.
+#' @examples
+#' make_mark("mark_spoke", ggplot2::geom_spoke)
+#' # Now usable in pipeline:
+#' \dontrun{
+#' df |> plotit(encode(x = x, y = y, radius = r, angle = a)) |> mark_spoke()
+#' }
+#' @export
+make_mark <- function(name, geom_fun) {
+  if (!is.character(name) || length(name) != 1) {
+    cli::cli_abort("{.arg name} must be a single string.")
+  }
+  if (!grepl("^mark_", name)) {
+    cli::cli_warn(
+      "{.arg name} should start with 'mark_', got {.val {name}}."
+    )
+  }
+
+  generic <- S7::new_generic(
+    name, "plot",
+    function(plot, mapping = NULL, data = NULL, position = NULL, ...,
+             rasterize = FALSE, rasterize_dpi = 300, rasterize_dev = "cairo") {
+      S7::S7_dispatch()
+    }
+  )
+  ._register_mark_method(generic, geom_fun)
+  invisible(generic)
+}
+
+# ---- make_theme ----
+#' Create a reusable theme preset
+#'
+#' Builds a theme function from `ggplot2::theme()` elements and
+#' an optional base theme. The returned function applies the theme
+#' to a plotit object and can be used anywhere `style()` is used.
+#'
+#' @param name Name for the theme function as a string
+#'   (e.g. `"style_dark"`).
+#' @param ... Theme elements passed to [ggplot2::theme()].
+#' @param base_theme A base ggplot2 theme function
+#'   (default: [ggplot2::theme_minimal]).
+#' @return Invisibly returns the created function.
+#' @examples
+#' style_dark <- make_theme("style_dark",
+#'   plot.background = ggplot2::element_rect(fill = "#1a1a1a"),
+#'   text = ggplot2::element_text(colour = "white"))
+#' \dontrun{
+#' plotit(iris, encode(x = Sepal.Width, y = Sepal.Length)) |>
+#'   mark_point() |> style_dark()
+#' }
+#' @export
+make_theme <- function(name, ..., base_theme = ggplot2::theme_minimal) {
+  force(name)
+  force(base_theme)
+  dots <- rlang::list2(...)
+
+  fun <- function(plot, base_size = NULL, base_family = NULL) {
+    thm <- base_theme(
+      base_size = base_size %||% 11,
+      base_family = base_family %||% ""
+    ) + do.call(ggplot2::theme, dots)
+    plot@gg <- plot@gg + thm
+    plot
+  }
+  assign(name, fun, envir = parent.frame())
+  invisible(fun)
+}

man/make_mark.Rd

@@ -469,3 +469,34 @@ test_that("mark_corr supports no-reorder", {
   p <- plotit(mtcars, encode()) |> mark_corr(reorder = FALSE)
   expect_s3_class(p, "plotit::plotit")
 })
+
+# ---- make_mark / make_theme ----
+test_that("make_mark creates a usable custom mark", {
+  generic <- make_mark("mark_tile_test", ggplot2::geom_tile)
+  df <- expand.grid(x = 1:3, y = 1:3)
+  df$z <- 1:9
+  p <- generic(plotit(df, encode(x = x, y = y, fill = z)))
+  expect_s3_class(p, "plotit::plotit")
+  expect_length(.built(p)$data, 1)
+})
+
+test_that("make_mark warns on non-mark_ name", {
+  expect_warning(make_mark("foo_bar", ggplot2::geom_point))
+})
+
+test_that("make_theme creates a usable theme function", {
+  style_test <- make_theme("style_test",
+    plot.title = ggplot2::element_text(colour = "blue"))
+  p <- plotit(iris, encode(x = Sepal.Width, y = Sepal.Length)) |>
+    mark_point() |> label_title("Test") |> style_test()
+  expect_s3_class(p, "plotit::plotit")
+})
+
+test_that("make_theme with custom base theme works", {
+  style_custom <- make_theme("style_custom",
+    panel.grid.major = ggplot2::element_line(colour = "grey90"),
+    base_theme = ggplot2::theme_bw)
+  p <- plotit(iris, encode(x = Sepal.Width, y = Sepal.Length)) |>
+    mark_point() |> style_custom()
+  expect_s3_class(p, "plotit::plotit")
+})