Repurpose rect key (#6327)

* default linewidth to 0

* draw_key_rect treats NA-fill as missing

* swap raster key

* accept snapshots

* lol at my incompetence

* add news bullet

* accept snapshot change

Author: teunbrand

NEWS.md

@@ -333,6 +333,8 @@
   to retrieve the class via constructor functions (@teunbrand).
 * (internal) The ViewScale class has a `make_fixed_copy()` method to permit 
   copying trained position scales (#3441).
+* `draw_key_rect()` replaces a `NA` fill by the `colour` aesthetic and 
+  `draw_key_polygon()` has 0 linewidth as internal default (@teunbrand, #5385).
 * Improved consistency of curve direction in `geom_curve()` (@teunbrand, #5069)
 * `linetype = NA` is now interpreted to mean 'no line' instead of raising errors
   (@teunbrand, #6269).

R/geom-raster.R

@@ -127,5 +127,5 @@ GeomRaster <- ggproto("GeomRaster", Geom,
       default.units = "native", interpolate = interpolate
     )
   },
-  draw_key = draw_key_rect
+  draw_key = draw_key_polygon
 )

R/legend-draw.R

@@ -54,20 +54,18 @@ draw_key_abline <- function(data, params, size) {
 #' @export
 #' @rdname draw_key
 draw_key_rect <- function(data, params, size) {
+  colour <- if (is.na(data$fill %||% NA)) data$colour
   rectGrob(gp = gg_par(
     col = NA,
-    fill = fill_alpha(data$fill %||% data$colour %||% "grey20", data$alpha),
+    fill = fill_alpha(colour %||% "grey20", data$alpha),
     lty = data$linetype %||% 1
   ))
 }
 #' @export
 #' @rdname draw_key
 draw_key_polygon <- function(data, params, size) {
-  if (is.null(data$linewidth)) {
-    data$linewidth <- 0.5
-  }
 
-  lwd <- data$linewidth
+  lwd <- data$linewidth %||% 0
 
   grob <- rectGrob(
     width = unit(1, "npc") - unit(lwd, "mm"),