grid.grab(warn = 2, wrap = FALSE, ...)
grid.grabExpr(expr, warn = 2, wrap = FALSE, ...)TRUE, each non-grob element on the
display list is captured by wrapping it in a grob.
There are two functions for capturing output:
use grid.grab to capture an existing drawing
and grid.grabExpr to capture the output from
an expression (without drawing anything).
For each of these functions, the output can be captured in two ways. One way tries to be clever and make a gTree with a childrenvp slot containing all viewports on the display list (including those that are popped) and every grob on the display list as a child of the new gTree; each child has a vpPath in the vp slot so that it is drawn in the appropriate viewport. In other words, the gTree contains all elements on the display list, but in a slightly altered form.
The other way, wrap=TRUE,
is to create a grob for every element on the
display list (and make all of those grobs children of the
gTree).
The first approach creates a more compact and elegant gTree, which is more flexible to work with, but is not guaranteed to faithfully replicate all possible grid output. The second approach is more brute force, and harder to work with, but should always faithfully replicate the original output.
gTree
pushViewport(viewport(w=.5, h=.5))
grid.rect()
grid.points(stats::runif(10), stats::runif(10))
popViewport()
grab <- grid.grab()
grid.newpage()
grid.draw(grab)
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