graphics.off()

df <- data.frame(time=as.numeric(time(Nile)), flow=as.numeric(Nile))

library(ggplot2)
library(gridSVG)
library(XML)

thePlot <- ggplot(df, aes(x=time, y=flow)) + geom_line()
botPlot <- thePlot +
           scale_y_continuous(breaks=c(600, 1200)) +
           opts(plot.background=theme_rect(colour="transparent"),
                axis.title.y=theme_text(colour="white", size=6),
                axis.title.x=theme_blank())

# The basic plot layout
doplot <- function() {
    pushViewport(viewport(y=1, height=.8, just="top", 
                          name="topvp"))
    print(thePlot, newpage=FALSE)
    upViewport()
    pushViewport(viewport(y=0, height=.2, just="bottom", 
                          name="bottomvp"))
    print(botPlot, newpage=FALSE)
    upViewport()
}

# Scale factor: W/w
# The *plotRegion* in the top plot is this factor times the
# plotRegion in the bottom plot
scale <- 4

# SVG version
plotWidth <- 7
pdf("normalplot.pdf", width=plotWidth, height=plotWidth)
doplot()
# Determine the width of the margins in the main plot
# Does not matter which "panel-3-3" I get because they are both the same
downViewport("panel-3-3")
plotRegionWidth <- convertWidth(unit(1, "npc"), "inches", valueOnly=TRUE)
marginWidth <- plotWidth - plotRegionWidth
# Add semitrasparent "thumb" rect
# Need to get the right "panel-3-3" this time
upViewport(0)
downViewport("bottomvp")
downViewport("panel-3-3")
rg <- rectGrob(x=0, width=1/scale, just="left",
               gp=gpar(col=rgb(0,0,1,.5), fill=rgb(0,0,1,.2)),
               name="thumb")
# Thumb ONLY captures mouseDown events
# MouseUp and mouseMove events are capture anywhere on the image
# (see below)
thumb <- garnishGrob(rg,
                     onmousedown="thumbDown(evt)")
# MouseUp and mouseMove events are also captured anywhere on the image
grid.set("plot.background.rect",
         garnishGrob(grid.get("plot.background.rect",
                              grep=TRUE),
                     onmouseup="mUp(evt)",
                     onmousemove=paste("mMove(evt, ", scale, ")", sep="")),
         grep=TRUE)
grid.draw(thumb)
grid.script(filename="slider.js")
gridToSVG("normalplot.svg")
dev.off()

# Wide version 
pdf("wideplot.pdf", width=plotRegionWidth*scale + marginWidth)
doplot()
gridToSVG("wideplot.svg")
dev.off()

# Read in both SVG files, extract the top plot region from
# the wide version and use that to replace the plot region
# in the main version
normalSVG <- xmlParse("normalplot.svg")
wideSVG <- xmlParse("wideplot.svg")

normalPlotSVG <- getNodeSet(normalSVG,
                            "//svg:g[@id='panel-3-3.1']",
                            c(svg="http://www.w3.org/2000/svg"))[[1]]
widePlotSVG <- getNodeSet(wideSVG,
                          "//svg:g[@id='panel-3-3.1']/svg:g[@id='panel-3-3']",
                          c(svg="http://www.w3.org/2000/svg"))[[1]]
# To set clip attribute for axis viewport,
# need the x, y, width, height from background rect for panel-3-3
# (which is first <rect> below panel-3-3)
# BEFORE we replace that with the one from fancyWide.svg!
panelBg  <- getNodeSet(normalPlotSVG,
                       ".//svg:rect",
                       c(svg="http://www.w3.org/2000/svg"))[[1]]
# Replace panel-3-3 in original plot with wide version
removeChildren(normalPlotSVG, "g")
addChildren(normalPlotSVG, widePlotSVG)
# Do same thing for x-axis
normalAxisSVG <- getNodeSet(normalSVG,
                            "//svg:g[@id='axis_h-5-3.1']",
                            c(svg="http://www.w3.org/2000/svg"))[[1]]
wideAxisSVG <-
    getNodeSet(wideSVG,
               "//svg:g[@id='axis_h-5-3.1']/svg:g[@id='axis_h-5-3']",
               c(svg="http://www.w3.org/2000/svg"))[[1]]
removeChildren(normalAxisSVG, "g")
addChildren(normalAxisSVG, wideAxisSVG)
# Set a clip region for the x-axis on the top plot
axisClipRectAttrs <- xmlAttrs(panelBg)[c("x", "y", "width", "height")]
axisClipRectAttrs["height"] <- axisClipRectAttrs["y"]
axisClipRectAttrs["y"] <- 0
addChildren(normalAxisSVG,
            newXMLNode("clipPath",
                       newXMLNode("rect",
                                  attrs=axisClipRectAttrs),
                       attrs=c(id="axis_h-5-3.1-clip")))
addAttributes(normalAxisSVG,
              "clip-path"="url(#axis_h-5-3.1-clip)")
# Set event handling for entire image
addAttributes(getNodeSet(normalSVG, "/svg:svg",
                         c(svg="http://www.w3.org/2000/svg"))[[1]],
              onmouseup="mUp(evt)",
              onmousemove=paste("mMove(evt, ", scale, ")", sep=""))

saveXML(normalSVG, file="sliderplot.svg")