R: Encapsulate calculations and generating a grob

grid.delay {grid}

R Documentation

Encapsulate calculations and generating a grob

Description

Evaluates an expression that includes both calculations and generating a grob that depends on the calculations so that both the calculations and the grob generation will be rerun when the scene is redrawn (e.g., device resize or editing).

Intended only for expert use.

Usage

delayGrob(expr, list, name=NULL, gp=NULL, vp=NULL)
grid.delay(expr, list, name=NULL, gp=NULL, vp=NULL)

Arguments

`expr`	object of mode `expression` or `call` or an unevaluated expression.
`list`	a list defining the environment in which `expr` is to be evaluated.
`name`	A character identifier.
`gp`	An object of class `gpar`, typically the output from a call to the function `gpar`. This is basically a list of graphical parameter settings.
`vp`	A Grid viewport object (or NULL).

Details

A grob is created of special class "delayedgrob" (and drawn, in the case of grid.delay). The makeContent method for this class evaluates the expression with the list as the evaluation environment (and the grid Namespace as the parent of that environment).

The expr argument should return a grob as its result.

These functions are analogues of the grid.record() and recordGrob() functions; the difference is that these functions are based on the makeContent() hook, while those functions are based on the drawDetails() hook.

Note

This function must be used instead of the function recordGraphics; all of the dire warnings about using recordGraphics responsibly also apply here.

Author(s)

Paul Murrell

Examples

grid.delay({
              w <- convertWidth(unit(1, "inches"), "npc")
              rectGrob(width=w)
            },
            list())

[Package grid version 3.4.1 Index]