From 958fc445227aec4404607d58302133a8d2f1ba60 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Mon, 13 Nov 2023 11:39:11 +0100
Subject: [PATCH 1/9] transform midpoint

---
 R/scale-gradient.R | 20 +++++++++++++++-----
 R/scale-steps.R    | 18 ++++++++++++++----
 2 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/R/scale-gradient.R b/R/scale-gradient.R
index 95ee2824b2..2c01832ec6 100644
--- a/R/scale-gradient.R
+++ b/R/scale-gradient.R
@@ -95,26 +95,36 @@ scale_fill_gradient <- function(..., low = "#132B43", high = "#56B1F7", space =
 #' @rdname scale_gradient
 #' @export
 scale_colour_gradient2 <- function(..., low = muted("red"), mid = "white", high = muted("blue"),
-                                   midpoint = 0, space = "Lab", na.value = "grey50", guide = "colourbar",
+                                   midpoint = 0, space = "Lab", na.value = "grey50",
+                                   trans = "identity", guide = "colourbar",
                                    aesthetics = "colour") {
+  trans <- as.trans(trans)
+  trans_mid <- trans$transform(midpoint)
+  check_transformation(midpoint, trans_mid, trans$name, call = expr(midpoint))
+
   continuous_scale(
     aesthetics,
     palette = div_gradient_pal(low, mid, high, space),
-    na.value = na.value, guide = guide, ...,
-    rescaler = mid_rescaler(mid = midpoint)
+    na.value = na.value, trans = trans, guide = guide, ...,
+    rescaler = mid_rescaler(mid = trans_mid)
   )
 }
 
 #' @rdname scale_gradient
 #' @export
 scale_fill_gradient2 <- function(..., low = muted("red"), mid = "white", high = muted("blue"),
-                                 midpoint = 0, space = "Lab", na.value = "grey50", guide = "colourbar",
+                                 midpoint = 0, space = "Lab", na.value = "grey50",
+                                 trans = "identity", guide = "colourbar",
                                  aesthetics = "fill") {
+  trans <- as.trans(trans)
+  trans_mid <- trans$transform(midpoint)
+  check_transformation(midpoint, trans_mid, trans$name, call = expr(midpoint))
+
   continuous_scale(
     aesthetics,
     palette = div_gradient_pal(low, mid, high, space),
     na.value = na.value, guide = guide, ...,
-    rescaler = mid_rescaler(mid = midpoint)
+    rescaler = mid_rescaler(mid = trans_mid)
   )
 }
 
diff --git a/R/scale-steps.R b/R/scale-steps.R
index 5bbba07cb9..146503a6ed 100644
--- a/R/scale-steps.R
+++ b/R/scale-steps.R
@@ -52,10 +52,15 @@ scale_colour_steps <- function(..., low = "#132B43", high = "#56B1F7", space = "
 #' @rdname scale_steps
 #' @export
 scale_colour_steps2 <- function(..., low = muted("red"), mid = "white", high = muted("blue"),
-                                midpoint = 0, space = "Lab", na.value = "grey50", guide = "coloursteps",
+                                midpoint = 0, space = "Lab", na.value = "grey50",
+                                trans = "identity", guide = "coloursteps",
                                 aesthetics = "colour") {
+  trans <- as.trans(trans)
+  trans_mid <- trans$transform(midpoint)
+  check_transformation(midpoint, trans_mid, trans$name, call = expr(midpoint))
+
   binned_scale(aesthetics, palette = div_gradient_pal(low, mid, high, space),
-               na.value = na.value, guide = guide, rescaler = mid_rescaler(mid = midpoint), ...)
+               na.value = na.value, guide = guide, rescaler = mid_rescaler(mid = trans_mid), ...)
 }
 #' @rdname scale_steps
 #' @export
@@ -75,10 +80,15 @@ scale_fill_steps <- function(..., low = "#132B43", high = "#56B1F7", space = "La
 #' @rdname scale_steps
 #' @export
 scale_fill_steps2 <- function(..., low = muted("red"), mid = "white", high = muted("blue"),
-                              midpoint = 0, space = "Lab", na.value = "grey50", guide = "coloursteps",
+                              midpoint = 0, space = "Lab", na.value = "grey50",
+                              trans = "identity", guide = "coloursteps",
                               aesthetics = "fill") {
+  trans <- as.trans(trans)
+  trans_mid <- trans$transform(midpoint)
+  check_transformation(midpoint, trans_mid, trans$name, call = expr(midpoint))
+
   binned_scale(aesthetics, palette = div_gradient_pal(low, mid, high, space),
-               na.value = na.value, guide = guide, rescaler = mid_rescaler(mid = midpoint), ...)
+               na.value = na.value, guide = guide, rescaler = mid_rescaler(mid = trans_mid), ...)
 }
 #' @rdname scale_steps
 #' @export

From 1ad3b3f28a9a666bd2b75099ca2e54685384e80e Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Mon, 13 Nov 2023 11:39:18 +0100
Subject: [PATCH 2/9] add test

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

diff --git a/tests/testthat/test-scale-gradient.R b/tests/testthat/test-scale-gradient.R
index fafa2226fe..8e661dc0fa 100644
--- a/tests/testthat/test-scale-gradient.R
+++ b/tests/testthat/test-scale-gradient.R
@@ -9,3 +9,19 @@ test_that("points outside the limits are plotted as NA", {
   correct_fill <- c("#B26D65", "#DCB4AF", "orange")
   expect_equal(layer_data(p)$fill, correct_fill)
 })
+
+test_that("midpoints are transformed", {
+
+  scale <- scale_colour_gradient2(midpoint = 1, trans = "identity")
+  scale$train(c(0, 3))
+  expect_equal(scale$rescale(c(0, 3)), c(0.25, 1))
+
+  scale <- scale_colour_gradient2(midpoint = 10, trans = "log10")
+  scale$train(scale$transform(c(0, 1000)))
+  ans <- scale$rescale(c(0, 3), c(0.25, 1))
+
+  expect_warning(
+    scale_colour_gradient2(midpoint = 0, trans = "log10"),
+    "introduced infinite values"
+  )
+})

From 799280ceadbe6885fb611f37714a0e2a9dd44de1 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Mon, 13 Nov 2023 11:48:58 +0100
Subject: [PATCH 3/9] check_transformation takes an argument name to report

---
 R/scale-.R | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/R/scale-.R b/R/scale-.R
index eb4248048d..70262119ab 100644
--- a/R/scale-.R
+++ b/R/scale-.R
@@ -1286,13 +1286,17 @@ scale_flip_position <- function(scale) {
   invisible()
 }
 
-check_transformation <- function(x, transformed, name, call = NULL) {
-  if (any(is.finite(x) != is.finite(transformed))) {
-    cli::cli_warn(
-      "{.field {name}} transformation introduced infinite values.",
-      call = call
-    )
+check_transformation <- function(x, transformed, name, arg = NULL, call = NULL) {
+  if (!any(is.finite(x) != is.finite(transformed))) {
+    return(invisible())
+  }
+  if (is.null(arg)) {
+    end <- "."
+  } else {
+    end <- paste0(" in {.arg {arg}}.")
   }
+  msg <- paste0("{.field {name}} transformation introduced infinite values", end)
+  cli::cli_warn(msg, call = call)
 }
 
 trans_support_nbreaks <- function(trans) {

From 17bbfb114dbb440d19a0a5fd1859b95f73da8353 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Mon, 13 Nov 2023 11:49:29 +0100
Subject: [PATCH 4/9] handle transformation in `mid_rescaler()`

---
 R/scale-gradient.R | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/R/scale-gradient.R b/R/scale-gradient.R
index 2c01832ec6..c8759acb8e 100644
--- a/R/scale-gradient.R
+++ b/R/scale-gradient.R
@@ -128,9 +128,16 @@ scale_fill_gradient2 <- function(..., low = muted("red"), mid = "white", high =
   )
 }
 
-mid_rescaler <- function(mid) {
+mid_rescaler <- function(mid, trans = "identity",
+                         arg = caller_arg(mid), call = caller_env()) {
+  trans <- as.trans(trans)
+  trans_mid <- trans$transform(mid)
+  check_transformation(
+    mid, trans_mid, trans$name,
+    arg = arg, call = call
+  )
   function(x, to = c(0, 1), from = range(x, na.rm = TRUE)) {
-    rescale_mid(x, to, from, mid)
+    rescale_mid(x, to, from, trans_mid)
   }
 }
 

From ac3501d4f5d00765c9e004a45e89d30122a72681 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Mon, 13 Nov 2023 11:49:56 +0100
Subject: [PATCH 5/9] repeat less

---
 R/scale-gradient.R | 14 +++-----------
 R/scale-steps.R    | 12 ++++--------
 2 files changed, 7 insertions(+), 19 deletions(-)

diff --git a/R/scale-gradient.R b/R/scale-gradient.R
index c8759acb8e..fe3ccefb7c 100644
--- a/R/scale-gradient.R
+++ b/R/scale-gradient.R
@@ -98,15 +98,11 @@ scale_colour_gradient2 <- function(..., low = muted("red"), mid = "white", high
                                    midpoint = 0, space = "Lab", na.value = "grey50",
                                    trans = "identity", guide = "colourbar",
                                    aesthetics = "colour") {
-  trans <- as.trans(trans)
-  trans_mid <- trans$transform(midpoint)
-  check_transformation(midpoint, trans_mid, trans$name, call = expr(midpoint))
-
   continuous_scale(
     aesthetics,
     palette = div_gradient_pal(low, mid, high, space),
     na.value = na.value, trans = trans, guide = guide, ...,
-    rescaler = mid_rescaler(mid = trans_mid)
+    rescaler = mid_rescaler(mid = midpoint, trans = trans)
   )
 }
 
@@ -116,15 +112,11 @@ scale_fill_gradient2 <- function(..., low = muted("red"), mid = "white", high =
                                  midpoint = 0, space = "Lab", na.value = "grey50",
                                  trans = "identity", guide = "colourbar",
                                  aesthetics = "fill") {
-  trans <- as.trans(trans)
-  trans_mid <- trans$transform(midpoint)
-  check_transformation(midpoint, trans_mid, trans$name, call = expr(midpoint))
-
   continuous_scale(
     aesthetics,
     palette = div_gradient_pal(low, mid, high, space),
-    na.value = na.value, guide = guide, ...,
-    rescaler = mid_rescaler(mid = trans_mid)
+    na.value = na.value, trans = trans, guide = guide, ...,
+    rescaler = mid_rescaler(mid = midpoint, trans = trans)
   )
 }
 
diff --git a/R/scale-steps.R b/R/scale-steps.R
index 146503a6ed..9e5f148936 100644
--- a/R/scale-steps.R
+++ b/R/scale-steps.R
@@ -55,12 +55,10 @@ scale_colour_steps2 <- function(..., low = muted("red"), mid = "white", high = m
                                 midpoint = 0, space = "Lab", na.value = "grey50",
                                 trans = "identity", guide = "coloursteps",
                                 aesthetics = "colour") {
-  trans <- as.trans(trans)
-  trans_mid <- trans$transform(midpoint)
-  check_transformation(midpoint, trans_mid, trans$name, call = expr(midpoint))
 
   binned_scale(aesthetics, palette = div_gradient_pal(low, mid, high, space),
-               na.value = na.value, guide = guide, rescaler = mid_rescaler(mid = trans_mid), ...)
+               na.value = na.value, trans = trans, guide = guide,
+               rescaler = mid_rescaler(mid = midpoint, trans = trans), ...)
 }
 #' @rdname scale_steps
 #' @export
@@ -83,12 +81,10 @@ scale_fill_steps2 <- function(..., low = muted("red"), mid = "white", high = mut
                               midpoint = 0, space = "Lab", na.value = "grey50",
                               trans = "identity", guide = "coloursteps",
                               aesthetics = "fill") {
-  trans <- as.trans(trans)
-  trans_mid <- trans$transform(midpoint)
-  check_transformation(midpoint, trans_mid, trans$name, call = expr(midpoint))
 
   binned_scale(aesthetics, palette = div_gradient_pal(low, mid, high, space),
-               na.value = na.value, guide = guide, rescaler = mid_rescaler(mid = trans_mid), ...)
+               na.value = na.value, trans = trans, guide = guide,
+               rescaler = mid_rescaler(mid = midpoint, trans = trans), ...)
 }
 #' @rdname scale_steps
 #' @export

From f1139d97b877e4117daeaa2963ddd847bdd29e65 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Mon, 13 Nov 2023 11:54:06 +0100
Subject: [PATCH 6/9] add news bullet

---
 NEWS.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index a15a099b5c..9a39263527 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,9 @@
 # ggplot2 (development version)
 
+* (breaking) In the `scale_{colour/fill}_gradient2()` and 
+  `scale_{colour/fill}_steps2()` functions, the `midpoint` argument is 
+  transformed by the scale transformation (#3198).
+
 * In the theme element hierarchy, parent elements that are a strict subclass
   of child elements now confer their subclass upon the children (#5457).
 

From 1f2d38585ae496ab0a39f9ba16ef1276c8c6fd29 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Mon, 13 Nov 2023 12:55:28 +0100
Subject: [PATCH 7/9] redocument

---
 R/scale-gradient.R    |  1 +
 man/scale_gradient.Rd | 27 +++++++++++++++------------
 man/scale_steps.Rd    | 27 +++++++++++++++------------
 3 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/R/scale-gradient.R b/R/scale-gradient.R
index fe3ccefb7c..1ca4291cd2 100644
--- a/R/scale-gradient.R
+++ b/R/scale-gradient.R
@@ -90,6 +90,7 @@ scale_fill_gradient <- function(..., low = "#132B43", high = "#56B1F7", space =
 }
 
 #' @inheritParams scales::div_gradient_pal
+#' @inheritParams continuous_scale
 #' @param midpoint The midpoint (in data value) of the diverging scale.
 #'   Defaults to 0.
 #' @rdname scale_gradient
diff --git a/man/scale_gradient.Rd b/man/scale_gradient.Rd
index 35d57f2b68..98f541b08f 100644
--- a/man/scale_gradient.Rd
+++ b/man/scale_gradient.Rd
@@ -46,6 +46,7 @@ scale_colour_gradient2(
   midpoint = 0,
   space = "Lab",
   na.value = "grey50",
+  trans = "identity",
   guide = "colourbar",
   aesthetics = "colour"
 )
@@ -58,6 +59,7 @@ scale_fill_gradient2(
   midpoint = 0,
   space = "Lab",
   na.value = "grey50",
+  trans = "identity",
   guide = "colourbar",
   aesthetics = "fill"
 )
@@ -159,18 +161,6 @@ bounds values with \code{NA}.
 \item \code{\link[scales:oob]{scales::squish()}} for squishing out of bounds values into range.
 \item \code{\link[scales:oob]{scales::squish_infinite()}} for squishing infinite values into range.
 }}
-    \item{\code{trans}}{For continuous scales, the name of a transformation object
-or the object itself. Built-in transformations include "asn", "atanh",
-"boxcox", "date", "exp", "hms", "identity", "log", "log10", "log1p", "log2",
-"logit", "modulus", "probability", "probit", "pseudo_log", "reciprocal",
-"reverse", "sqrt" and "time".
-
-A transformation object bundles together a transform, its inverse,
-and methods for generating breaks and labels. Transformation objects
-are defined in the scales package, and are called \verb{<name>_trans}. If
-transformations require arguments, you can call them from the scales
-package, e.g. \code{\link[scales:boxcox_trans]{scales::boxcox_trans(p = 2)}}.
-You can create your own transformation with \code{\link[scales:trans_new]{scales::trans_new()}}.}
     \item{\code{expand}}{For position scales, a vector of range expansion constants used to add some
 padding around the data to ensure that they are placed some distance
 away from the axes. Use the convenience function \code{\link[=expansion]{expansion()}}
@@ -203,6 +193,19 @@ same time, via \code{aesthetics = c("colour", "fill")}.}
 \item{midpoint}{The midpoint (in data value) of the diverging scale.
 Defaults to 0.}
 
+\item{trans}{For continuous scales, the name of a transformation object
+or the object itself. Built-in transformations include "asn", "atanh",
+"boxcox", "date", "exp", "hms", "identity", "log", "log10", "log1p", "log2",
+"logit", "modulus", "probability", "probit", "pseudo_log", "reciprocal",
+"reverse", "sqrt" and "time".
+
+A transformation object bundles together a transform, its inverse,
+and methods for generating breaks and labels. Transformation objects
+are defined in the scales package, and are called \verb{<name>_trans}. If
+transformations require arguments, you can call them from the scales
+package, e.g. \code{\link[scales:boxcox_trans]{scales::boxcox_trans(p = 2)}}.
+You can create your own transformation with \code{\link[scales:trans_new]{scales::trans_new()}}.}
+
 \item{colours, colors}{Vector of colours to use for n-colour gradient.}
 
 \item{values}{if colours should not be evenly positioned along the gradient
diff --git a/man/scale_steps.Rd b/man/scale_steps.Rd
index 4ce18b6839..60764819af 100644
--- a/man/scale_steps.Rd
+++ b/man/scale_steps.Rd
@@ -30,6 +30,7 @@ scale_colour_steps2(
   midpoint = 0,
   space = "Lab",
   na.value = "grey50",
+  trans = "identity",
   guide = "coloursteps",
   aesthetics = "colour"
 )
@@ -63,6 +64,7 @@ scale_fill_steps2(
   midpoint = 0,
   space = "Lab",
   na.value = "grey50",
+  trans = "identity",
   guide = "coloursteps",
   aesthetics = "fill"
 )
@@ -142,18 +144,6 @@ bounds values with \code{NA}.
 \item \code{\link[scales:oob]{scales::squish()}} for squishing out of bounds values into range.
 \item \code{\link[scales:oob]{scales::squish_infinite()}} for squishing infinite values into range.
 }}
-    \item{\code{trans}}{For continuous scales, the name of a transformation object
-or the object itself. Built-in transformations include "asn", "atanh",
-"boxcox", "date", "exp", "hms", "identity", "log", "log10", "log1p", "log2",
-"logit", "modulus", "probability", "probit", "pseudo_log", "reciprocal",
-"reverse", "sqrt" and "time".
-
-A transformation object bundles together a transform, its inverse,
-and methods for generating breaks and labels. Transformation objects
-are defined in the scales package, and are called \verb{<name>_trans}. If
-transformations require arguments, you can call them from the scales
-package, e.g. \code{\link[scales:boxcox_trans]{scales::boxcox_trans(p = 2)}}.
-You can create your own transformation with \code{\link[scales:trans_new]{scales::trans_new()}}.}
     \item{\code{expand}}{For position scales, a vector of range expansion constants used to add some
 padding around the data to ensure that they are placed some distance
 away from the axes. Use the convenience function \code{\link[=expansion]{expansion()}}
@@ -186,6 +176,19 @@ same time, via \code{aesthetics = c("colour", "fill")}.}
 \item{midpoint}{The midpoint (in data value) of the diverging scale.
 Defaults to 0.}
 
+\item{trans}{For continuous scales, the name of a transformation object
+or the object itself. Built-in transformations include "asn", "atanh",
+"boxcox", "date", "exp", "hms", "identity", "log", "log10", "log1p", "log2",
+"logit", "modulus", "probability", "probit", "pseudo_log", "reciprocal",
+"reverse", "sqrt" and "time".
+
+A transformation object bundles together a transform, its inverse,
+and methods for generating breaks and labels. Transformation objects
+are defined in the scales package, and are called \verb{<name>_trans}. If
+transformations require arguments, you can call them from the scales
+package, e.g. \code{\link[scales:boxcox_trans]{scales::boxcox_trans(p = 2)}}.
+You can create your own transformation with \code{\link[scales:trans_new]{scales::trans_new()}}.}
+
 \item{colours, colors}{Vector of colours to use for n-colour gradient.}
 
 \item{values}{if colours should not be evenly positioned along the gradient

From 46401b3b3adb7911b751578c31e0b82a312ab867 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Mon, 13 Nov 2023 12:59:51 +0100
Subject: [PATCH 8/9] Better call wiring

---
 R/scale-.R                           | 2 +-
 tests/testthat/test-scale-gradient.R | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/R/scale-.R b/R/scale-.R
index 70262119ab..7696f51639 100644
--- a/R/scale-.R
+++ b/R/scale-.R
@@ -583,7 +583,7 @@ check_breaks_labels <- function(breaks, labels, call = NULL) {
 
 default_transform <- function(self, x) {
   new_x <- self$trans$transform(x)
-  check_transformation(x, new_x, self$trans$name, self$call)
+  check_transformation(x, new_x, self$trans$name, call = self$call)
   new_x
 }
 
diff --git a/tests/testthat/test-scale-gradient.R b/tests/testthat/test-scale-gradient.R
index 8e661dc0fa..01cbebd9ab 100644
--- a/tests/testthat/test-scale-gradient.R
+++ b/tests/testthat/test-scale-gradient.R
@@ -17,7 +17,7 @@ test_that("midpoints are transformed", {
   expect_equal(scale$rescale(c(0, 3)), c(0.25, 1))
 
   scale <- scale_colour_gradient2(midpoint = 10, trans = "log10")
-  scale$train(scale$transform(c(0, 1000)))
+  scale$train(scale$transform(c(1, 1000)))
   ans <- scale$rescale(c(0, 3), c(0.25, 1))
 
   expect_warning(

From b383fa38434a3067eb229b70aa8a23c4e8c2ef94 Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Thu, 14 Dec 2023 12:53:49 +0100
Subject: [PATCH 9/9] update trans -> transform

---
 tests/testthat/test-scale-gradient.R | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/testthat/test-scale-gradient.R b/tests/testthat/test-scale-gradient.R
index 01cbebd9ab..d37cb6d80d 100644
--- a/tests/testthat/test-scale-gradient.R
+++ b/tests/testthat/test-scale-gradient.R
@@ -21,7 +21,7 @@ test_that("midpoints are transformed", {
   ans <- scale$rescale(c(0, 3), c(0.25, 1))
 
   expect_warning(
-    scale_colour_gradient2(midpoint = 0, trans = "log10"),
+    scale_colour_gradient2(midpoint = 0, transform = "log10"),
     "introduced infinite values"
   )
 })