R: Encapsulate calculations and drawing

grid.record {grid} | R Documentation

## Encapsulate calculations and drawing

### Description

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

Intended only for expert use.

### Usage

    recordGrob(expr, list, name=NULL, gp=NULL, vp=NULL)
    grid.record(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 `"recordedGrob"` (and drawn, in the case of `grid.record`). The `drawDetails` method for this class evaluates the expression with the list as the evaluation environment (and the grid Namespace as the parent of that environment).

### 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

### See Also

`recordGraphics`

### Examples

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

[Package grid version 2.8.1 Index]