[R] grid: Grid graphics flickering

[Paul Murrell]

Hi

Two points:

1.  grid.remove() redraws the entire scene (and because the drawing is 
slow you see a flicker)

2.  Doing this ...

dev.hold()
grid.gremove("lastShape")
dev.flush()

... may reduce flicker for you.

Paul

On 07/25/13 06:10, Daniel Guetta wrote:
> I'm designing an interactive plot using the `grid` package in R. As
> part of the interactivity, I repeatedly delete and re-create various
> parts of the plot. However, the total number of grid elements (as
> obtained using the `grid.ls()` command) stays constant; everything I
> create was previously removed.
>
> The problem is as follows - once I've gone through a few cycles of
> creation and deletion, every deletion I make to the graphic, however
> small, causes all the interactive parts of the plot (those I've been
> repeatedly deleting and creating) to flicker.
>
> Here's the simplest example I could come up with - first run this code
> to set up the `grid` graphic, and repeatedly delete and re-create
> certain elements
>
> ###############################
>
>      library(grid)
>
>      pushViewport(viewport())
>
>      for (x in seq(0, 1, length=5))
>      {
>      for (y in seq(0, 1, length=5))
>      {
>      pushViewport(viewport(x = x, y = y, width=1/5, height=1/5,
> name=paste("foo", x, y, sep="")))
>      grid.rect()
>
>      pushViewport(viewport(x = 0, 0, width=1/4, height=1/4, name="bar1"))
>      grid.circle(name="testing")
>      grid.text("123")
>      upViewport()
>
>      pushViewport(viewport(x = 1, 0, width=1/4, height=1/4, name="bar2"))
>      grid.circle(name="testing")
>      grid.text("123")
>      upViewport()
>
>      pushViewport(viewport(x = 0, 1, width=1/4, height=1/4, name="bar3"))
>      grid.circle(name="testing")
>      grid.text("123")
>      upViewport()
>
>      pushViewport(viewport(x = 1, 1, width=1/4, height=1/4, name="bar4"))
>      grid.circle(name="testing")
>      grid.text("123")
>      upViewport()
>
>      upViewport()
>      }
>      }
>
>      for (i in 1:10)
>      {
>
>      grid.gremove("testing")
>
>      for (x in seq(0, 1, length=5))
>      {
>      for (y in seq(0, 1, length=5))
>      {
>      downViewport(paste("foo", x, y, sep=""))
>
>      downViewport("bar1"); grid.circle(name="testing"); upViewport()
>      downViewport("bar2"); grid.circle(name="testing"); upViewport()
>      downViewport("bar3"); grid.circle(name="testing"); upViewport()
>      downViewport("bar4"); grid.circle(name="testing"); upViewport()
>
>      upViewport()
>      }
>      }
>
>      }
>
> ###############################
>
> Once this is all set up, create a new arbitrary square on the device
>
> ###############################
>      grid.rect(height=0.5, width=0.5, gp=gpar(lty = 2), name = "lastShape")
> ###############################
>
> Now try to delete it
>
> ###############################
>      grid.gremove("lastShape")
> ###############################
>
> Notice that when you run this last deletion command, all the small
> circles that I've been creating and deleting flicker slightly, even
> though I haven't touched them. This makes the entire graphic very
> distracting.
>
> The thing is, if I don't delete and re-create the original graphics so
> many times, this doesn't happen! So I figure I must be leaving a trail
> somewhere because of inefficient deleting.
>
> Any ideas how to prevent that?
>
> Thanks a million!
>
> ------------------------------------------------------
>
> Daniel Guetta
> PhD Candidate, Columbia University
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
Auckland
New Zealand
64 9 3737599 x85392
paul at stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/