From a2ef967f5dff2ff5ead0da2f8fee4eb3d60aff79 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Thu, 19 Sep 2024 15:06:39 +0200
Subject: [PATCH 1/7] inheritance of NA-margins

---
 R/theme.R | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/R/theme.R b/R/theme.R
index 43c379f9b6..b094f30f8b 100644
--- a/R/theme.R
+++ b/R/theme.R
@@ -864,6 +864,15 @@ combine_elements <- function(e1, e2) {
     return(e1)
   }
 
+  if (inherits(e1, "margin") && inherits(e2, "margin")) {
+    if (anyNA(e2)) {
+      e2[is.na(e2)] <- unit(0, "pt")
+    }
+    if (anyNA(e1)) {
+      e1[is.na(e1)] <- e2[is.na(e1)]
+    }
+  }
+
   # If neither of e1 or e2 are element_* objects, return e1
   if (!inherits(e1, "element") && !inherits(e2, "element")) {
     return(e1)
@@ -893,6 +902,10 @@ combine_elements <- function(e1, e2) {
     e1$linewidth <- e2$linewidth * unclass(e1$linewidth)
   }
 
+  if (inherits(e1, "element_text")) {
+    e1$margin <- combine_elements(e1$margin, e2$margin)
+  }
+
   # If e2 is 'richer' than e1, fill e2 with e1 parameters
   if (is.subclass(e2, e1)) {
     new <- defaults(e1, e2)

From 4ce398f5427dfed332001209d9dee4c9f7b8568c Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Thu, 19 Sep 2024 15:33:09 +0200
Subject: [PATCH 2/7] add `part_margin()` function

---
 NAMESPACE          | 1 +
 R/margins.R        | 7 +++++++
 R/theme-elements.R | 2 +-
 man/element.Rd     | 5 ++++-
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/NAMESPACE b/NAMESPACE
index f0ccf3bec1..7f3120db86 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -496,6 +496,7 @@ export(new_guide)
 export(old_guide)
 export(panel_cols)
 export(panel_rows)
+export(part_margin)
 export(pattern_alpha)
 export(position_dodge)
 export(position_dodge2)
diff --git a/R/margins.R b/R/margins.R
index 176072b4de..2640b8e1c5 100644
--- a/R/margins.R
+++ b/R/margins.R
@@ -8,6 +8,13 @@ margin <- function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
   class(u) <- c("margin", class(u))
   u
 }
+
+#' @rdname element
+#' @export
+part_margin <- function(t = NA, r = NA, b = NA, l = NA, unit = "pt") {
+  margin(t = t, r = r, b = b, l = l, unit = unit)
+}
+
 is.margin <- function(x) {
   inherits(x, "margin")
 }
diff --git a/R/theme-elements.R b/R/theme-elements.R
index 747bb0cf78..abcd2168b2 100644
--- a/R/theme-elements.R
+++ b/R/theme-elements.R
@@ -11,7 +11,7 @@
 #'   - `element_geom()`: defaults for drawing layers.
 #'
 #' `rel()` is used to specify sizes relative to the parent,
-#' `margin()` is used to specify the margins of elements.
+#' `margin()` and `part_margin()` are used to specify the margins of elements.
 #'
 #' @param fill Fill colour.
 #' @param colour,color Line/border colour. Color is an alias for colour.
diff --git a/man/element.Rd b/man/element.Rd
index adb1b7eb22..4bbb1d492c 100644
--- a/man/element.Rd
+++ b/man/element.Rd
@@ -8,6 +8,7 @@
 \alias{element_geom}
 \alias{rel}
 \alias{margin}
+\alias{part_margin}
 \title{Theme elements}
 \usage{
 element_blank()
@@ -66,6 +67,8 @@ element_geom(
 rel(x)
 
 margin(t = 0, r = 0, b = 0, l = 0, unit = "pt")
+
+part_margin(t = NA, r = NA, b = NA, l = NA, unit = "pt")
 }
 \arguments{
 \item{fill}{Fill colour.}
@@ -145,7 +148,7 @@ specify the display of how non-data components of the plot are drawn.
 }
 
 \code{rel()} is used to specify sizes relative to the parent,
-\code{margin()} is used to specify the margins of elements.
+\code{margin()} and \code{part_margin()} are used to specify the margins of elements.
 }
 \examples{
 plot <- ggplot(mpg, aes(displ, hwy)) + geom_point()

From 63cc7e4c8979964d142dfe899dc0c73d6a13cf9e Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Thu, 19 Sep 2024 15:39:29 +0200
Subject: [PATCH 3/7] setup merge method for margins

---
 NAMESPACE            |  1 +
 R/theme.R            | 12 ++++++++++++
 man/merge_element.Rd |  3 +++
 3 files changed, 16 insertions(+)

diff --git a/NAMESPACE b/NAMESPACE
index 7f3120db86..4696b0e590 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -96,6 +96,7 @@ S3method(makeContext,dotstackGrob)
 S3method(merge_element,default)
 S3method(merge_element,element)
 S3method(merge_element,element_blank)
+S3method(merge_element,margin)
 S3method(pattern_alpha,GridPattern)
 S3method(pattern_alpha,GridTilingPattern)
 S3method(pattern_alpha,default)
diff --git a/R/theme.R b/R/theme.R
index b094f30f8b..7e3f30995a 100644
--- a/R/theme.R
+++ b/R/theme.R
@@ -831,6 +831,18 @@ merge_element.element <- function(new, old) {
   new
 }
 
+#' @rdname merge_element
+#' @export
+merge_element.margin <- function(new, old) {
+  if (is.null(old) || inherits(old, "element_blank")) {
+    return(new)
+  }
+  if (anyNA(new)) {
+    new[is.na(new)] <- old[is.na(new)]
+  }
+  new
+}
+
 #' Combine the properties of two elements
 #'
 #' @param e1 An element object
diff --git a/man/merge_element.Rd b/man/merge_element.Rd
index 4071e6c69a..ca993eeec3 100644
--- a/man/merge_element.Rd
+++ b/man/merge_element.Rd
@@ -5,6 +5,7 @@
 \alias{merge_element.default}
 \alias{merge_element.element_blank}
 \alias{merge_element.element}
+\alias{merge_element.margin}
 \title{Merge a parent element into a child element}
 \usage{
 merge_element(new, old)
@@ -14,6 +15,8 @@ merge_element(new, old)
 \method{merge_element}{element_blank}(new, old)
 
 \method{merge_element}{element}(new, old)
+
+\method{merge_element}{margin}(new, old)
 }
 \arguments{
 \item{new}{The child element in the theme hierarchy}

From 1fb967d4331db71622048dd8b866379eb3c9a80f Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Thu, 19 Sep 2024 15:40:50 +0200
Subject: [PATCH 4/7] add test

---
 tests/testthat/test-theme.R | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/tests/testthat/test-theme.R b/tests/testthat/test-theme.R
index 36ad577c65..9d11740620 100644
--- a/tests/testthat/test-theme.R
+++ b/tests/testthat/test-theme.R
@@ -616,6 +616,22 @@ test_that("complete_theme completes a theme", {
   reset_theme_settings()
 })
 
+test_that("part_margin() mechanics work as expected", {
+
+  t <- theme_gray() +
+    theme(plot.margin = part_margin(b = 11))
+
+  test <- calc_element("plot.margin", t)
+  expect_equal(as.numeric(test), c(5.5, 5.5, 11, 5.5))
+
+  t <- theme_gray() +
+    theme(margins = part_margin(b = 11))
+
+  test <- calc_element("plot.margin", t)
+  expect_equal(as.numeric(test), c(5.5, 5.5, 11, 5.5))
+
+})
+
 # Visual tests ------------------------------------------------------------
 
 test_that("aspect ratio is honored", {

From ad51647a072dfea40dd55a9bc8df91b31cc9e23e Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Thu, 19 Sep 2024 15:43:06 +0200
Subject: [PATCH 5/7] add news bullet

---
 NEWS.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index 5df6059f0f..1d09ca6b13 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* Theme margins can have NA-units to inherit from parent elements. The new
+  function `part_margin()` has NA-units as default (@teunbrand, #6155)
 * Built-in `theme_*()` functions now have `ink` and `paper` arguments to control
   foreground and background colours respectively (@teunbrand)
 * The `summary()` method for ggplots is now more terse about facets 

From b4987341844adc9342ea4e9192b60c48f6964748 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Fri, 20 Sep 2024 08:48:47 +0200
Subject: [PATCH 6/7] rename `part_margin()` to `margin_part()`

---
 NAMESPACE      | 2 +-
 R/margins.R    | 2 +-
 man/element.Rd | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/NAMESPACE b/NAMESPACE
index 4696b0e590..304e7ef6ac 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -485,6 +485,7 @@ export(layer_sf)
 export(lims)
 export(map_data)
 export(margin)
+export(margin_part)
 export(max_height)
 export(max_width)
 export(mean_cl_boot)
@@ -497,7 +498,6 @@ export(new_guide)
 export(old_guide)
 export(panel_cols)
 export(panel_rows)
-export(part_margin)
 export(pattern_alpha)
 export(position_dodge)
 export(position_dodge2)
diff --git a/R/margins.R b/R/margins.R
index 2640b8e1c5..a6637f3e57 100644
--- a/R/margins.R
+++ b/R/margins.R
@@ -11,7 +11,7 @@ margin <- function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
 
 #' @rdname element
 #' @export
-part_margin <- function(t = NA, r = NA, b = NA, l = NA, unit = "pt") {
+margin_part <- function(t = NA, r = NA, b = NA, l = NA, unit = "pt") {
   margin(t = t, r = r, b = b, l = l, unit = unit)
 }
 
diff --git a/man/element.Rd b/man/element.Rd
index 4bbb1d492c..b6e530d198 100644
--- a/man/element.Rd
+++ b/man/element.Rd
@@ -8,7 +8,7 @@
 \alias{element_geom}
 \alias{rel}
 \alias{margin}
-\alias{part_margin}
+\alias{margin_part}
 \title{Theme elements}
 \usage{
 element_blank()
@@ -68,7 +68,7 @@ rel(x)
 
 margin(t = 0, r = 0, b = 0, l = 0, unit = "pt")
 
-part_margin(t = NA, r = NA, b = NA, l = NA, unit = "pt")
+margin_part(t = NA, r = NA, b = NA, l = NA, unit = "pt")
 }
 \arguments{
 \item{fill}{Fill colour.}

From 4cf042682b48008460b06b15a19abd2035e1912d Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Fri, 20 Sep 2024 08:48:47 +0200
Subject: [PATCH 7/7] rename `part_margin()` to `margin_part()`

---
 NAMESPACE                   | 2 +-
 NEWS.md                     | 2 +-
 R/margins.R                 | 2 +-
 R/theme-elements.R          | 2 +-
 man/element.Rd              | 6 +++---
 tests/testthat/test-theme.R | 6 +++---
 6 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/NAMESPACE b/NAMESPACE
index 4696b0e590..304e7ef6ac 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -485,6 +485,7 @@ export(layer_sf)
 export(lims)
 export(map_data)
 export(margin)
+export(margin_part)
 export(max_height)
 export(max_width)
 export(mean_cl_boot)
@@ -497,7 +498,6 @@ export(new_guide)
 export(old_guide)
 export(panel_cols)
 export(panel_rows)
-export(part_margin)
 export(pattern_alpha)
 export(position_dodge)
 export(position_dodge2)
diff --git a/NEWS.md b/NEWS.md
index 1d09ca6b13..0bc74080a1 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,7 +1,7 @@
 # ggplot2 (development version)
 
 * Theme margins can have NA-units to inherit from parent elements. The new
-  function `part_margin()` has NA-units as default (@teunbrand, #6155)
+  function `margin_part()` has NA-units as default (@teunbrand, #6155)
 * Built-in `theme_*()` functions now have `ink` and `paper` arguments to control
   foreground and background colours respectively (@teunbrand)
 * The `summary()` method for ggplots is now more terse about facets 
diff --git a/R/margins.R b/R/margins.R
index 2640b8e1c5..a6637f3e57 100644
--- a/R/margins.R
+++ b/R/margins.R
@@ -11,7 +11,7 @@ margin <- function(t = 0, r = 0, b = 0, l = 0, unit = "pt") {
 
 #' @rdname element
 #' @export
-part_margin <- function(t = NA, r = NA, b = NA, l = NA, unit = "pt") {
+margin_part <- function(t = NA, r = NA, b = NA, l = NA, unit = "pt") {
   margin(t = t, r = r, b = b, l = l, unit = unit)
 }
 
diff --git a/R/theme-elements.R b/R/theme-elements.R
index abcd2168b2..05e882a078 100644
--- a/R/theme-elements.R
+++ b/R/theme-elements.R
@@ -11,7 +11,7 @@
 #'   - `element_geom()`: defaults for drawing layers.
 #'
 #' `rel()` is used to specify sizes relative to the parent,
-#' `margin()` and `part_margin()` are used to specify the margins of elements.
+#' `margin()` and `margin_part()` are used to specify the margins of elements.
 #'
 #' @param fill Fill colour.
 #' @param colour,color Line/border colour. Color is an alias for colour.
diff --git a/man/element.Rd b/man/element.Rd
index 4bbb1d492c..6d78b6ae1e 100644
--- a/man/element.Rd
+++ b/man/element.Rd
@@ -8,7 +8,7 @@
 \alias{element_geom}
 \alias{rel}
 \alias{margin}
-\alias{part_margin}
+\alias{margin_part}
 \title{Theme elements}
 \usage{
 element_blank()
@@ -68,7 +68,7 @@ rel(x)
 
 margin(t = 0, r = 0, b = 0, l = 0, unit = "pt")
 
-part_margin(t = NA, r = NA, b = NA, l = NA, unit = "pt")
+margin_part(t = NA, r = NA, b = NA, l = NA, unit = "pt")
 }
 \arguments{
 \item{fill}{Fill colour.}
@@ -148,7 +148,7 @@ specify the display of how non-data components of the plot are drawn.
 }
 
 \code{rel()} is used to specify sizes relative to the parent,
-\code{margin()} and \code{part_margin()} are used to specify the margins of elements.
+\code{margin()} and \code{margin_part()} are used to specify the margins of elements.
 }
 \examples{
 plot <- ggplot(mpg, aes(displ, hwy)) + geom_point()
diff --git a/tests/testthat/test-theme.R b/tests/testthat/test-theme.R
index 9d11740620..a98c0fb3f7 100644
--- a/tests/testthat/test-theme.R
+++ b/tests/testthat/test-theme.R
@@ -616,16 +616,16 @@ test_that("complete_theme completes a theme", {
   reset_theme_settings()
 })
 
-test_that("part_margin() mechanics work as expected", {
+test_that("margin_part() mechanics work as expected", {
 
   t <- theme_gray() +
-    theme(plot.margin = part_margin(b = 11))
+    theme(plot.margin = margin_part(b = 11))
 
   test <- calc_element("plot.margin", t)
   expect_equal(as.numeric(test), c(5.5, 5.5, 11, 5.5))
 
   t <- theme_gray() +
-    theme(margins = part_margin(b = 11))
+    theme(margins = margin_part(b = 11))
 
   test <- calc_element("plot.margin", t)
   expect_equal(as.numeric(test), c(5.5, 5.5, 11, 5.5))