use is_align_free generic function to determine whether we should ali…

…gn observation

NAMESPACE

@@ -138,6 +138,9 @@ S3method(inherit_scheme,"NULL")
 S3method(inherit_scheme,scheme_align)
 S3method(inherit_scheme,scheme_data)
 S3method(inherit_scheme,scheme_theme)
+S3method(is_align_free,Align)
+S3method(is_align_free,Cross)
+S3method(is_align_free,Free)
 S3method(is_coord_okay,CoordCartesian)
 S3method(is_coord_okay,CoordTrans)
 S3method(is_coord_okay,default)

R/align-.R

@@ -176,7 +176,6 @@ summary.Align <- function(object, ...) {
 #' @rdname align
 #' @include plot-.R
 Align <- ggproto("Align", AlignProto,
-    free_align = FALSE,
     parameters = function(self) {
         c(
             align_method_params(

R/cross-.R

@@ -17,7 +17,6 @@ summary.Cross <- function(object, ...) c(TRUE, FALSE)
 #' @importFrom ggplot2 ggproto ggplot
 #' @include plot-.R
 Cross <- ggproto("Cross", AlignProto,
-    free_align = FALSE,
     layout = function(self, layout_data, layout_coords, layout_name) {
         if (is.null(.subset2(layout_coords, "nobs"))) {
             cli_abort(sprintf(

R/layout-.R

@@ -17,7 +17,7 @@ methods::setClass("LayoutProto",
         schemes = "list", # used to provide global parameters for all plots
         # control the layout, `theme` will also be used by `ggsave`
         titles = "list",
-        annotation = "list", # To-DO add `pacth_titles` for layout
+        annotation = "list", # To-Do add `pacth_titles` for layout
         theme = "ANY",
         `_namespace` = "ANY"
     ),

R/plot-.R

@@ -106,6 +106,17 @@ methods::setMethod("+", c("ggalign_plot", "ANY"), function(e1, e2) {
 #' @importFrom methods is
 is_ggalign_plot <- function(x) is(x, "ggalign_plot")
 
+is_align_free <- function(x) UseMethod("is_align_free")
+
+#' @export
+is_align_free.Align <- function(x) FALSE
+
+#' @export
+is_align_free.Cross <- function(x) FALSE
+
+#' @export
+is_align_free.Free <- function(x) TRUE
+
 #' Summary the action of `AlignProto`
 #'
 #' @param object A `AlignProto` object
@@ -119,9 +130,8 @@ summary.AlignProto <- function(object, ...) c(FALSE, FALSE)
 #' @importFrom ggplot2 ggproto
 AlignProto <- ggproto("AlignProto",
     locked = TRUE,
-    # A boolean value indicates whether this plot is free
-    # if `FALSE`, we'll check whether the layout need align observations
-    free_align = FALSE,
+    # we always prevent user from modifying the object in `$build_plot()` and
+    # `$finish_plot()` methods
     lock = function(self) {
         assign("locked", value = TRUE, envir = self)
     },
@@ -176,6 +186,7 @@ align_method_params <- function(f, remove = character()) {
 #' @export
 stack_layout_add.ggalign_plot <- function(object, stack, object_name) {
     align <- object@align
+    # To-Do: Use S7 and double dispatch
     if (is_cross(align) && !is_cross_layout(stack)) {
         # we prevent from adding `cross_*` to normal `stack_layout()`
         cli_abort(c(
@@ -188,7 +199,7 @@ stack_layout_add.ggalign_plot <- function(object, stack, object_name) {
     }
     if (is.null(active_index <- stack@active) ||
         is_ggalign_plot(plot <- .subset2(stack@plot_list, active_index))) {
-        if (is.null(old_coords <- stack@layout) && !align$free_align) {
+        if (is.null(old_coords <- stack@layout) && !is_align_free(align)) {
             cli_abort(c(
                 sprintf(
                     "Cannot add {.var {object_name}} to %s",
@@ -258,7 +269,7 @@ quad_layout_add.ggalign_plot <- function(object, quad, object_name) {
     # check if we can align in this direction
     direction <- to_direction(position)
     align <- object@align
-    if (!align$free_align && is.null(slot(quad, direction))) {
+    if (!is_align_free(align) && is.null(slot(quad, direction))) {
         cli_abort(c(
             sprintf(
                 "Cannot add {.var {object_name}} to %s", object_name(quad)