Clean up proj.fill code

R/geom-magnify.R

@@ -383,32 +383,7 @@ GeomMagnify <- ggproto("GeomMagnify", Geom,
     proj_fill_grob <- if (is.null(proj.fill) || identical(proj, "single")) {
       NULL
     } else {
-      line_pair_idx <- seq(1L, nrow(proj_df), by = 2L)
-      # each 2 rows of proj_df define a pair of matched projection lines
-      proj_fill_grobs <- lapply(line_pair_idx,
-                                function (idx) {
-        # the two lines go in opposite directions (would be nice to clarify
-        # or remove this brittle long-range dependency)
-        # this lets us easily define a polygon
-        x <- c(proj_df$x[idx], proj_df$xend[idx],
-               proj_df$xend[idx + 1], proj_df$x[idx + 1])
-        y <- c(proj_df$y[idx], proj_df$yend[idx],
-               proj_df$yend[idx + 1], proj_df$y[idx + 1])
-
-        proj_fill_grob <- polygonGrob(x = x, y = y,
-                                 default.units = "native")
-        proj_fill_grob <- gridGeometry::polyclipGrob(proj_fill_grob, target_grob,
-                                                     op = "minus",
-                                                     gp = gpar(
-                                   col  = "transparent",
-                                   fill = proj.fill,
-                                   lty  = proj.linetype,
-                                   lwd  = linewidth * .pt))
-        proj_fill_grob
-      })
-      grob_glist <- do.call(gList, proj_fill_grobs)
-      gTree(children = grob_glist)
-      # TODO check with grobs, maps etc
+      make_proj_fill_grob(proj_df, target_grob, proj.fill)
     }
 
     if (shadow) {

R/projection.R

@@ -274,3 +274,37 @@ calculate_proj_df_rect <- function(proj, data, corners, coord, panel_params) {
   df <- data.frame(x = proj_x, y = proj_y, xend = proj_xend, yend = proj_yend)
   coord$transform(df, panel_params)
 }
+
+
+#' Creates a grob to fill between the projection lines
+#'
+#' @param proj_df Data frame returned from calculate_proj_df_*.
+#'   This should have n pairs of matched projection lines,
+#'   both going in the same direction (i.e. from target to inset or vice versa)
+#' @param target_grob From [draw_panel()].
+#' @param fill The fill colour
+#'
+#' @return The grob, excluding the target grob.
+#' @noRd
+make_proj_fill_grob <- function (proj_df, target_grob, fill) {
+  line_pair_idx <- seq(1L, nrow(proj_df), by = 2L)
+
+  proj_fill_grobs <- lapply(line_pair_idx,
+                            function (idx) {
+    x <- c(proj_df$x[idx],
+           proj_df$xend[idx],
+           proj_df$xend[idx + 1],
+           proj_df$x[idx + 1])
+    y <- c(proj_df$y[idx],
+           proj_df$yend[idx],
+           proj_df$yend[idx + 1],
+           proj_df$y[idx + 1])
+
+    unclipped_grob <- polygonGrob(x = x, y = y, default.units = "native")
+    gridGeometry::polyclipGrob(unclipped_grob, target_grob, op = "minus",
+                               gp = gpar(col  = "transparent", fill = fill))
+  })
+
+  proj_fill_grobs <- do.call(gList, proj_fill_grobs)
+  gTree(children = proj_fill_grobs)
+}