R Under development (unstable) (2021-06-17 r80510) -- "Unsuffered Consequences"
Copyright (C) 2021 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(grid)
> 
> ## Set up
> grid.newpage()
> pushViewport(viewport(name="a.vp"))
> grid.rect(name="a.grob")
> 
> ## Default finds only grobs (no vpPath)
> result <- grid.grep("a", grep=TRUE, global=TRUE)
> result
[[1]]
a.grob 

> attr(result[[1]], "vpPath")
[1] ""
> 
> ## 'viewports = TRUE' (and 'vpPath = TRUE')
> ## finds grobs and viewports (AND vpPath on grobs)
> result <- grid.grep("a", grep=TRUE, global=TRUE, viewports=TRUE)
> result
[[1]]
a.vp 

[[2]]
a.grob 

> attr(result[[2]], "vpPath")
[1] "a.vp"
> 
> ## 'viewports = FALSE' and 'vpPath = TRUE'
> ## finds only grobs AND vpPath on grobs
> result <- grid.grep("a", grep=TRUE, global=TRUE, vpPath=TRUE)
> result
[[1]]
a.grob 

> attr(result[[1]], "vpPath")
[1] "a.vp"
> 
> ## 'viewports = TRUE' and 'vpPath = FALSE'
> ## finds viewports and grobs (no vpPath)
> result <- grid.grep("a", grep=TRUE, global=TRUE, viewports=TRUE, vpPath=FALSE)
> result
[[1]]
a.vp 

[[2]]
a.grob 

> attr(result[[2]], "vpPath")
[1] ""
> 
> ###########################
> ## global=FALSE versions
> 
> ## grob (no vpPath)
> result <- grid.grep("a", grep=TRUE)
> result
a.grob 
> attr(result, "vpPath")
[1] ""
> ## viewport (NULL vpPath)
> result <- grid.grep("a", grep=TRUE, viewports=TRUE)
> result
a.vp 
> attr(result, "vpPath")
NULL
> ## grob with vpPath
> result <- grid.grep("a", grep=TRUE, vpPath=TRUE)
> result
a.grob 
> attr(result, "vpPath")
[1] "a.vp"
> ## viewport (NULL vpPath)
> result <- grid.grep("a", grep=TRUE, viewports=TRUE, vpPath=FALSE)
> result
a.vp 
> attr(result, "vpPath")
NULL
> 
> proc.time()
   user  system elapsed 
  0.238   0.032   0.255