merge guide legends depend on legend.position.inside only

Author: Yunuuuu

R/guide-colorbar.R

@@ -225,8 +225,7 @@ GuideColourbar <- ggproto(
     ticks                = "legend.ticks",
     ticks_length         = "legend.ticks.length",
     frame                = "legend.frame",
-    inside_position      = "legend.position.inside",
-    inside_justification = "legend.justification.inside"
+    inside_position      = "legend.position.inside"
   ),
 
   extract_key = function(scale, aesthetic, ...) {

R/guide-legend.R

@@ -181,8 +181,7 @@ GuideLegend <- ggproto(
     text_position        = "legend.text.position",
     title_position       = "legend.title.position",
     byrow                = "legend.byrow",
-    inside_position      = "legend.position.inside",
-    inside_justification = "legend.justification.inside"
+    inside_position      = "legend.position.inside"
   ),
 
   extract_params = function(scale, params,
@@ -344,14 +343,7 @@ GuideLegend <- ggproto(
       )
     )
     elements$text <- calc_element("legend.text", add_theme(theme, text))
-    ans <- Guide$setup_elements(params, elements, theme)
-    ans$inside_justification <- .subset2(
-      theme, "legend.justification.inside"
-    ) %||% .subset2(ans, "inside_position")
-    ans$inside_justification <- valid.just(.subset2(
-      ans, "inside_justification"
-    ))
-    ans
+    Guide$setup_elements(params, elements, theme)
   },
 
   override_elements = function(params, elements, theme) {
@@ -571,12 +563,12 @@ GuideLegend <- ggproto(
         t = 1, r = -1, b = -1, l = 1, z = -Inf
       )
     }
-    # attach the `position` and `justification` for the inside legends
+
+    # for inside guide legends, we also save the position values 
+    # in this way, we can identify legends with same position
+    # and then merge them into same guide box in `Guides$draw()`
     if (identical(.subset2(params, "position"), "inside")) {
       attr(gt, "inside_position") <- .subset2(elements, "inside_position")
-      attr(gt, "inside_justification") <- .subset2(
-        elements, "inside_justification"
-      )
     }
     gt
   }

R/guides-.R

@@ -531,13 +531,12 @@ Guides <- ggproto(
         theme = theme, position = positions[i],
         direction = directions[i], params = params[[i]]
       )
+      # we'll merge inside legends with same coordinate into same guide box
+      # here, we define the groups of the inside legends
       if (identical(positions[i], "inside")) {
         positions[i] <- paste(
           "inside",
           paste(attr(.subset2(grobs, i), "inside_position"), collapse = "_"),
-          paste(attr(.subset2(grobs, i), "inside_justification"), 
-            collapse = "_"
-          ),
           sep = "_"
         )
       }
@@ -548,6 +547,9 @@ Guides <- ggproto(
       levels = c(.trbl, unique(positions[startsWith(positions, "inside")]))
     )
     keep <- !vapply(grobs, is.zero, logical(1), USE.NAMES = FALSE)
+
+    # we grouped the legends by the positions
+    # for inside legends, they'll be splitted by the actual inside coordinate
     split(grobs[keep], positions[keep])
   },
 
@@ -586,10 +588,8 @@ Guides <- ggproto(
     global_just <- paste0("legend.justification.", position)
     global_just <- valid.just(calc_element(global_just, theme))
     if (startsWith(position, "inside")) {
-      # The position of inside legends are set by their justification
-      global_just <- attr(.subset2(grobs, 1L), "inside_justification") %||%
-        # fallback to original method of ggplot2 <=3.3.5
-        global_just
+      # for inside guide legends, the position was attached in
+      # each grob of the input grobs (which should share the same position)
       inside_position <- attr(.subset2(grobs, 1L), "inside_position") %||%
         # fallback to original method of ggplot2 <=3.3.5
         .subset2(theme, "legend.position.inside") %||% global_just