Stop ephemeral theme from clobbering persistent one

NEWS.md

@@ -235,6 +235,9 @@ related to plot layering. See "Bug fixes" below.
 
 ### Bug fixes
 
+- An ephemeral `theme` argument no longer clobbers a persistent `tinytheme()`
+  i.e., beyond the intended single plot override. Similarly for a user's own
+  `tpar()` settings. (#739 @grantmcdermott)
 - Annotations and layers added after a plot that used an ephemeral `theme`
   argument are no longer clipped to the wrong region. Only triggered once an
   intervening annotation changed `xpd` (e.g. `box()`, `mtext()`, or

R/tinyplot.R

@@ -922,6 +922,13 @@ tinyplot.default = function(
 
   # Ephemeral theme
   if (!is.null(theme)) {
+    # Capture the outgoing theme before the ephemeral one replaces it. `opar`
+    # carries base par values only, so the theme's *name* is not among them.
+    ptheme = tinytheme_get()
+    # tinytheme() calls init_tpar(), which wipes .tpar wholesale -- taking any
+    # user tpar() settings with it. An ephemeral theme should leave no trace,
+    # so snapshot the settings here and put them back on exit. (#739)
+    ptpar = as.list(.tpar)
     if (is.character(theme) && length(theme) == 1) {
       tinytheme(theme)
     } else if (is.list(theme)) {
@@ -934,12 +941,32 @@ tinyplot.default = function(
       # clobbered. Only needed for "default" theme which uses hook = FALSE
       # and thus sets par(mar) immediately. (#557)
       par(mar = opar$mar)
-      on.exit(init_tpar(rm_hook = TRUE), add = TRUE)
+      on.exit({
+        init_tpar(rm_hook = TRUE)
+        # init_tpar() wipes .tpar wholesale, so a persistent theme has to be
+        # reset explicitly. (#739)
+        if (!identical(ptheme, "default")) tinytheme(ptheme)
+        reset_tpar(ptpar)
+      }, add = TRUE)
     } else {
       dtheme = theme_default
       otheme = opar[names(dtheme)]
       on.exit({
-        do.call(tinytheme, otheme)
+        if (identical(ptheme, "default")) {
+          # No persistent theme was active. reset_tpar() below restores .tpar
+          # wholesale, so all that is left here is to drop the ephemeral
+          # theme's hooks and hand the user's own par settings back directly.
+          init_tpar(rm_hook = TRUE)
+          upar = otheme[!is.na(names(otheme))]
+          if (length(upar) > 0) par(upar)
+        } else {
+          # A persistent theme *was* active, so restore it by name. We must
+          # not splat `opar` on top: those are the theme's pre-hook par values,
+          # so passing them back as overrides would clobber the very theme we
+          # are restoring. (#739)
+          tinytheme(ptheme)
+        }
+        reset_tpar(ptpar)
         restore_plot_region(opar[["mar"]]) # See #629
       }, add = TRUE)
     }

R/tpar.R

@@ -474,3 +474,15 @@ init_tpar = function(rm_hook = FALSE) {
 ## initialize internal environment for tpar variables
 .tpar = new.env()
 init_tpar()
+
+
+# Restore a snapshot of .tpar taken with as.list(). Used to roll back an
+# ephemeral theme, whose tinytheme() calls wipe .tpar via init_tpar() and would
+# otherwise discard the user's own tpar() settings along with it. (#739)
+reset_tpar = function(snapshot) {
+  nms = names(.tpar)
+  extra = nms[!nms %in% names(snapshot)]
+  if (length(extra) > 0) rm(list = extra, envir = .tpar)
+  list2env(snapshot, envir = .tpar)
+  invisible(NULL)
+}

R/zzz.R

@@ -55,6 +55,7 @@
     "iby",
     "ifacet",
     "labels",
+    "las",
     "legend",
     "legend_args",
     "legend_draw_flag",
@@ -107,6 +108,7 @@
     "xmin",
     "xmin_dep",
     "xpad",
+    "xpad_user",
     "y",
     "y_dep",
     "yaxb",
@@ -122,6 +124,7 @@
     "ymax_dep",
     "ymin",
     "ymin_dep",
-    "ypad"
+    "ypad",
+    "ypad_user"
   ))
 }

altdoc/pkgdown.yml

@@ -2,7 +2,7 @@ altdoc: 0.7.3
 pandoc: 3.10.2
 pkgdown: 2.1.3
 pkgdown_sha: ~
-last_built: 2026-09-19T23:23:30+0000
+last_built: 2026-09-21T04:24:20+0000
 urls:
   reference: https://grantmcdermott.com/tinyplot/man
   article: https://grantmcdermott.com/tinyplot/vignettes

inst/tinytest/test-tinytheme.R

@@ -224,6 +224,24 @@ f = function() {
 }
 expect_snapshot_plot(f, label = "tinytheme_ephemeral_clip_xpd")
 
+## an ephemeral theme should leave no trace (#739)
+
+pdf(NULL)
+
+# a persistent theme survives an ephemeral one
+tinytheme("classic")
+plt(1, theme = "dark")
+expect_equal(tinytheme_get(), "classic")
+
+# as do the user's own tpar() settings
+tpar(grid = TRUE)
+plt(1, theme = "dark")
+expect_true(isTRUE(tpar("grid")))
+
+tinytheme()
+invisible(dev.off())
+
+
 # User mar override respected under dynmar (#587)
 f = function() {
   tinytheme("dynamic", mar = c(5, 5, 5, 5))

vignettes/introduction.qmd

@@ -341,11 +341,6 @@ tinyplot(
 )
 ```
 
-```{r}
-#| include: false
-tinytheme("clean2")
-```
-
 Similarly, **tinyplot** also supports special types to fit models and display
 their predictions, along with confidence intervals. Here is a somewhat silly
 example where we fit a linear model to predict temperature by day of month.^[The
@@ -555,12 +550,6 @@ tinyplot(
 )
 ```
 
-
-```{r theme_again}
-#| include: false
-tinytheme("clean2")
-```
-
 ## Save and replay plots
 
 A final point to note is that **tinyplot** offers convenience features for