Add room around guide title (#2195)

* Add room around guide title (@baptiste)

* Update visual test SVGs

* Update hgap and vgap in guide-colorbar.r to match guide-legend.r

* New visual test SVGs to reflect modified legends in guide-colorbar.r

Author: karawoo

R/guide-colorbar.r

@@ -255,10 +255,6 @@ guide_gengrob.colorbar <- function(guide, theme) {
   barlength.c <- switch(guide$direction, "horizontal" = barwidth.c, "vertical" = barheight.c)
   nbreak <- nrow(guide$key)
 
-  # gap between keys etc
-  hgap <- c(convertWidth(unit(0.3, "lines"), "mm"))
-  vgap <- hgap
-
   grob.bar <-
     if (guide$raster) {
       image <- switch(guide$direction, horizontal = t(guide$bar$colour), vertical = rev(guide$bar$colour))
@@ -301,6 +297,10 @@ guide_gengrob.colorbar <- function(guide, theme) {
   title_height <- convertHeight(grobHeight(grob.title), "mm")
   title_height.c <- c(title_height)
 
+  # gap between keys etc
+  hgap <- width_cm(theme$legend.spacing.x  %||% unit(0.3, "line"))
+  vgap <- height_cm(theme$legend.spacing.y %||% 0.5 * unit(title_height, "cm"))
+  
   # label
   label.theme <- guide$label.theme %||% calc_element("legend.text", theme)
   grob.label <- {

R/guide-legend.r

@@ -298,10 +298,6 @@ guide_gengrob.legend <- function(guide, theme) {
 
   nbreak <- nrow(guide$key)
 
-  # gap between keys etc
-  hgap <- width_cm(unit(0.3, "lines"))
-  vgap <- hgap
-
   grob.title <- ggname("guide.title",
     element_grob(
       guide$title.theme %||% calc_element("legend.title", theme),
@@ -315,6 +311,10 @@ guide_gengrob.legend <- function(guide, theme) {
 
   title_width <- width_cm(grob.title)
   title_height <- height_cm(grob.title)
+  
+  # gap between keys etc
+  hgap <- width_cm(theme$legend.spacing.x  %||% unit(0.3, "line"))
+  vgap <- height_cm(theme$legend.spacing.y %||% 0.5 * unit(title_height, "cm"))
 
   # Labels
   if (!guide$label || is.null(guide$key$.label)) {

R/utilities-grid.r

@@ -26,7 +26,7 @@ width_cm <- function(x) {
 }
 height_cm <- function(x) {
   if (is.grob(x)) {
-    convertWidth(grobHeight(x), "cm", TRUE)
+    convertHeight(grobHeight(x), "cm", TRUE)
   } else if (is.unit(x)) {
     convertHeight(x, "cm", TRUE)
   } else if (is.list(x)) {