[Rd] Buggy trellis.focus() with xyplot ?

[Felix Andrews]

2008/11/20 Deepayan Sarkar <deepayan.sarkar at gmail.com>:
> On Wed, Nov 19, 2008 at 8:55 AM, Daniel Kornhauser
> <dkor at northwestern.edu> wrote:
>> Hi:
>>
>> (Tried to find a bug report about this issue, but was unable to find it, let
>> me know if this is a known issue)
>> I have been working on an interface to highlight xyplot panels on mouse
>> overs in JavaGD but I have stumbled with what seems to be a bug in
>> trellis.focus.
>> I am using R 2.8 with lattice 0.17-15
>>
>>
>> *** To replicate the bug:
>> 1.- display an xyplot. For example, from the xyplot help page:
>> library(lattice)
>> require(stats)
>> EE <- equal.count(ethanol$E, number=9, overlap=1/4)
>> ## Constructing panel functions on the fly; prepanel
>> xyplot(NOx ~ C | EE, data = ethanol,
>>       prepanel = function(x, y) prepanel.loess(x, y, span = 1),
>>       xlab = "Compression Ratio", ylab = "NOx (micrograms/J)",
>>       panel = function(x, y) {
>>           panel.grid(h=-1, v= 2)
>>           panel.xyplot(x, y)
>>           panel.loess(x,y, span=1)
>>       },
>>       aspect = "xy")
>> 2.- resize to window be rectangular and have large margins in the left hand
>> and right hand side.
>> 3.- run trellis.focus() and try to select the first or last panel, you
>> should observe that it does not select the right one.
>>
>> sidenotes:
>> There are other problems with the focus in JavaGD but I just wanted to
>> include a simple self contained example in this mail.
>> If you make the window smaller, trellis.focus() works fine, you have to make
>> it bigger than the initial size.
>>
>>
>> *** To Fix the bug:
>> I tried to fix this bug in interraction.R but I was unsuccesful.
>>
>> The problem should stem from the a bad calculation of the pads in the
>> follwoing lines :
>>        leftPad <-
>> convertX(sum(glayout$page.layout$widths[1:(colRange[1]-1)]), "npc",
>> valueOnly = TRUE)
>>        rightPad <-
>> convertX(sum(glayout$page.layout$widths[(colRange[2]+1):layCols]), "npc",
>> valueOnly = TRUE)
>>        topPad <-
>> convertY(sum(glayout$page.layout$heights[1:(rowRange[1]-1)]), "npc",
>> valueOnly = TRUE)
>>        botPad <-
>> convertY(sum(glayout$page.layout$heights[(rowRange[2]+1):layRows]), "npc",
>> valueOnly = TRUE)
>>
>> I was succesful in tweaking the follwing lines adding arbitrary constants to
>> make it work for a particular instance of a xyplot with a particular size of
>> a window
>>       clickXScaled <- (as.numeric(clickLoc$x) - leftPad + Danielconstant1)
>> / (1 - leftPad - rightPad  + Danielconstant1)
>>        ....
>>        clickYScaled <- (as.numeric(clickLoc$y) - botPad + Danielconstant2)
>> / (1 - botPad - topPad + Danielconstant3)
>> This is of course a useless fix, since you want the fix to work for any plot
>> with any window size, but I might be valuable information.
>>
>>
>> *** Questions:
>> - Is this a real bug ?
>> - Any suggestions for fixing it ?
>> - If it can't be fixed, is there a way around this bug ?
>> (For example, setting the margins to be zero and set a fixed size for the
>> xplot)
>
> It appears that the conversions used in the current implementation
> (contributed by Felix Andrews) don't work when aspect != "fill"
> (probably leading back to the use of 'respect = TRUE' in grid.layout).

Yep, my fault, didn't think it through.

> The right way to do this is to first go down to the subregion
> containing just the panels, and then locate the click location within
> it. But this requires a suitable viewport to be predefined.
>
> I have changed print.trellis to create such a dummy viewport
> (accessible by trellis.focus("figure")), and modified trellis.focus()
> to use it. I will test it a bit more before uploading a new version
> (and also give Felix a chance to see if this breaks anything in

It won't affect playwith; playwith now uses a different approach: a function
inViewport(x.px, y.px, viewport)
reports whether a click location in pixels is inside the given
viewport. I loop through each panel viewport and check whether the
click is inside.

> playwith etc.). To see if the fix works, you can try the svn copy at
>
> https://svn.r-project.org/R-packages/trunk/lattice
>
> -Deepayan
>


-- 
Felix Andrews / 安福立
http://www.neurofractal.org/felix/
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