document new method

Author: teunbrand

R/facet-.R

@@ -346,6 +346,49 @@ Facet <- ggproto("Facet", NULL,
 
   ## Layout$render() -------------------------------------------------------
 
+  #' @field draw_panel_content
+  #' **Description**
+  #'
+  #' A function method to assemble the panel contents. It delegates the
+  #' `draw_back()` and `draw_front()` methods, as well as `Coord$draw_panel()`.
+  #'
+  #' **Usage**
+  #' ```r
+  #' Facet$draw_panel_content(
+  #'   panels,
+  #'   layout,
+  #'   x_scales,
+  #'   y_scales,
+  #'   ranges,
+  #'   coord,
+  #'   theme,
+  #'   params,
+  #'   ...
+  #' )
+  #' ```
+  #' **Arguments**
+  #' \describe{
+  #'   \item{`panels`}{A list parallel to layers. Each element is another list
+  #'   with grobs for each panel, generated by `Layer$draw_geom()`.}
+  #'   \item{`layout`}{A data frame computed by the `compute_layout()` method.
+  #'   Typically contains the faceting variables, `ROW`, `COL`, `PANEL`,
+  #'   `SCALE_X` and `SCALE_Y` variables.}
+  #'   \item{`x_scales`,`y_scales`}{A list of panel scales for each `SCALE_X`
+  #'   and `SCALE_Y` level respectively.}
+  #'   \item{`ranges`}{A list of panel parameters from the
+  #'   `setup_panel_params()` augmented with position guides.}
+  #'   \item{`coord`}{A `<Coord>` ggproto object.}
+  #'   \item{`data`}{A list of data frames containing layer data.}
+  #'   \item{`theme`}{A [complete theme][complete_theme()] object.}
+  #'   \item{`params`}{A list of parameters coming from the `setup_params()`
+  #'   method.}
+  #'   \item{`...`}{Currently not in use.}
+  #' }
+  #'
+  #' **Value**
+  #'
+  #' A list of grobs, one for each level of the `PANEL` layout variable. Grob
+  #' can be `zeroGrob()` to draw nothing.
   draw_panel_content = function(self, panels, layout, x_scales, y_scales,
                                 ranges, coord, data, theme, params, ...) {
     facet_bg <- self$draw_back(