Avoid advancing RNG when creating agg devices

Author: gjhunt

R/agg_dev.R

@@ -427,7 +427,7 @@ agg_capture <- function(
   }
   dim <- get_dims(width, height, units, res)
   background <- if (missing(bg)) background else bg
-  name <- paste0('agg_capture_', sample(.Machine$integer.max, 1))
+  name <- basename(tempfile('agg_capture_'))
   .Call(
     "agg_capture_c",
     name,
@@ -504,7 +504,7 @@ agg_record <- function(
   }
   dim <- get_dims(width, height, units, res)
   background <- if (missing(bg)) background else bg
-  name <- paste0('agg_record_', sample(.Machine$integer.max, 1))
+  name <- basename(tempfile('agg_record_'))
   .Call(
     "agg_record_c",
     name,

tests/testthat/test-rng-state.R

@@ -0,0 +1,32 @@
+test_that("agg devices do not advance global RNG state on creation", {
+
+  set.seed(123)
+  dev <- agg_capture()
+  handle <- dev()
+  dev.off()
+  a1 <- runif(1)
+  b1 <- .Random.seed
+
+  set.seed(123)
+  a2 <- runif(1)
+  b2 <- .Random.seed
+
+  expect_equal(a1, a2)
+  expect_equal(b1, b2)
+})
+
+test_that("agg_record does not advance global RNG state on creation", {
+  # with ragg
+  set.seed(456)
+  agg_record()
+  dev.off()
+  a1 <- runif(1)
+  b1 <- .Random.seed
+
+  set.seed(456)
+  a2 <- runif(1)
+  b2 <- .Random.seed
+
+  expect_equal(a1, a2)
+  expect_equal(b1, b2)
+})