Use grid::roundrectGrob. Tweak adjustment to projection lines to be "…

…looser".

DESCRIPTION

@@ -19,7 +19,6 @@ Depends:
     R (>= 4.1.0)
 Imports:
     cli,
-    ggforce (>= 0.4.1.9000),
     ggplot2 (>= 3.3.4),
     grid,
     gridExtra,

NEWS.md

@@ -1,8 +1,8 @@
 
 # ggmagnify (development version)
 
-* New `corners` argument sets corner radius on target and inset.
-  - We now depend on the "ggforce" package.
+* New `corners` argument sets corner radius on target and inset. Thanks
+  to @thomasp85 for help with this.
 
 # ggmagnify 0.2.0
 

R/compute-shape-grob.R

@@ -57,8 +57,7 @@ compute_shape_grob.data.frame <- function (from, shape, corners, data, coord,
 compute_shape_grob.default <- function (from, shape, corners, data, coord,
                                         panel_params, expand) {
   if (shape == "rect") {
-    ggforce::shapeGrob(x = c(0, 0, 1, 1),
-                       y = c(0, 1, 1, 0), radius = corners)
+    grid::roundrectGrob(r = unit(corners, "snpc"))
   } else if (shape == "ellipse") {
     # resist the temptation to replace this with circleGrob. You need to
     # mess with it later.

R/geom-magnify.R

@@ -42,7 +42,8 @@ NULL
 #' @param shadow Logical. Draw a shadow behind the inset plot? Requires the
 #'   "ggfx" package.
 #' @param corners Numeric between 0 and 1. Radius of rounded corners for the
-#'   target area and inset. Only used if `shape` is `"rect"`.
+#'   target area and inset. Only used if `shape` is `"rect"`. 0.1 is a good
+#'   starting value.
 #' @param linetype,colour,alpha,linewidth Linetype, colour, alpha and linewidth
 #' for borders and projection lines.
 #' @param target.linetype,inset.linetype,proj.linetype Linetypes

R/projection.R

@@ -163,22 +163,28 @@ calculate_proj_df_rect <- function(proj, data, corners, coord, panel_params) {
   to_ymax <- data$to_ymax
 
   if (corners > 0 && ! identical(proj, "single")) {
-    # the 1 - 1/sqrt(2) adjustment gets to the midpoint of the
+    # a 1 - 1/sqrt(2) adjustment, c. 0.29, would get to the midpoint of the
     # rounded corner (at a 45 degree angle), calculated via Pythagoras.
-    # Not perfect.
-    adj <- 1 - 1/sqrt(2)
-    corn_adj_x <- corners * (xmax - xmin) * adj
-    corn_adj_y <- corners * (ymax - ymin) * adj
-    to_corn_adj_x <- corners * (to_xmax - to_xmin) * adj
-    to_corn_adj_y <- corners * (to_ymax - to_ymin) * adj
-    xmin <- xmin + corn_adj_x
-    xmax <- xmax - corn_adj_x
-    ymin <- ymin + corn_adj_y
-    ymax <- ymax - corn_adj_y
-    to_xmin <- to_xmin + to_corn_adj_x
-    to_xmax <- to_xmax - to_corn_adj_x
-    to_ymin <- to_ymin + to_corn_adj_y
-    to_ymax <- to_ymax - to_corn_adj_y
+    # This isn't perfect because lines don't always come in at 45 deg.
+    # An adj of 0.2 is a bit "looser" and should give fewer cases
+    # where projection lines end up inside the target area.
+    # The use of min() below reflects that corners is in "snpc" units:
+    # see ?grid::unit.
+    size <- min(xmax - xmin, ymax - ymin)
+    to_size <- min(to_xmax - to_xmin, to_ymax - to_ymin)
+    adj <- 0.2 # 1 - 1/sqrt(2)
+    corn_adj <- corners * size * adj
+    to_corn_adj <- corners * to_size * adj
+
+    xmin <- xmin + corn_adj
+    xmax <- xmax - corn_adj
+    ymin <- ymin + corn_adj
+    ymax <- ymax - corn_adj
+
+    to_xmin <- to_xmin + to_corn_adj
+    to_xmax <- to_xmax - to_corn_adj
+    to_ymin <- to_ymin + to_corn_adj
+    to_ymax <- to_ymax - to_corn_adj
   }
 
   x <- mean(c(xmin, xmax))