R Under development (unstable) (2025-07-22 r88445 ucrt) -- "Unsuffered Consequences"
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> library(grid)
> library(gridSVG)

Attaching package: 'gridSVG'

The following objects are masked from 'package:grid':

    linearGradient, pattern, radialGradient

The following object is masked from 'package:grDevices':

    dev.off

> 
> pdf(file = NULL)
> 
> # Create the definition of an opacity mask, in this case
> # it will just be a circle with a gradient fill.
> rg <- radialGradient(col = c("white", "black"))
> m <- mask(gradientFillGrob(circleGrob(), gradient = rg))
> 
> # Register the opacity mask so that we can refer to it and apply it.
> registerMask("circleMask", m)
> 
> # Creating a simple plot that will be masked to the circle
> sp <- gTree(name = "simplePlot",
+             children = gList(xaxisGrob(), yaxisGrob(),
+                              rectGrob(gp = gpar(fill = "grey"))),
+             vp = plotViewport())
> grid.draw(sp)
> 
> # Now lets mask it
> grid.mask("simplePlot", label = "circleMask")
> # Alternatively we could also do this which avoids the need to call
> # 'registerMask' explicitly
> # grid.mask("simplePlot", m)
> 
> grid.export("mask-simpleplot.svg")
> dev.off()
null device 
          1 
> 
> 
> # Now lets recreate the previous example using 'pushMask'
> pdf(file = NULL)
> # Clear previous mask reference
> gridSVG.newpage()
> 
> 
> # Create the definition of an opacity mask, in this case
> # it will just be a circle with a gradient fill.
> rg <- radialGradient(col = c("white", "black"))
> m <- mask(gradientFillGrob(circleGrob(), gradient = rg))
> 
> # Create a new masking context for this viewport
> pushMask(m)
> 
> # Creating a simple plot that will be masked to our current masking context
> sp <- gTree(name = "simplePlot",
+             children = gList(xaxisGrob(), yaxisGrob(),
+                              rectGrob(gp = gpar(fill = "grey"))),
+             vp = plotViewport())
> grid.draw(sp)
> 
> # End the masking context
> popMask()
> 
> grid.export("pushmask-simpleplot.svg")
> dev.off()
null device 
          1 
> 
> 
> 
> proc.time()
   user  system elapsed 
   0.90    0.14    1.01