Fixing tooltip='two\nlines' data not rendering issue

[suhaani-agarwal]

fixing #219

[suhaani-agarwal]

I investigated into this issue, and saw that there are two files - geom.r and z-animint-helpers.r
the write.table function is called with quote=FALSE:

 write.table(some.lines, tmp,
                    col.names=FALSE,
                    quote=FALSE, row.names=FALSE, sep="\t")

With quote=FALSE, any string written to the TSV is unquoted. This becomes a problem because the JS side uses d3.tsv to read per-chunk TSVs. If the TSV contains a newline inside a field, it gets split into multiple lines. That breaks the tabular layout, and D3 mis-parses the rows. As a result, points can disappear
Thats why the geom_point was not being rendered when aes(tooltip = "two\nlines") was given with aes(color)

an example is :

viz<-list(
  p1=ggplot()+
    geom_point(aes(
      x, x, tooltip=x, color=x),
      size=5,
      data.frame(x=c("one line", "two\nlines", "three\nlines\nhere")))
)

the generated tsv for this is as follows :

Here the "two\nlines" point is split across rows, which causes it to disappear.

When I changed those write.table calls to use quote=TRUE, the TSV instead looks like this:

This way, the newline stays inside the quoted string, and D3 reads the whole field correctly. The "two\nlines" point then renders properly, with the tooltip showing \n as a space as follows:

Screen.Recording.2025-09-01.at.7.26.43.PM.mov

[suhaani-agarwal]

Now the newline survives serialization, but the browser’s default rendering (and/or the way the tooltip is inserted into the DOM) collapses it into a single space. This happens not because the code explicitly replaces \n with a space, but because HTML collapses newlines by default.

We have a few options:

• Keep quote=TRUE (as I have now) and accept that \n renders as a space in tooltips.
• Keep quote=TRUE and implement multi-line tooltips by converting \n to <br> for proper HTML rendering.
• Revert to quote=FALSE and remove or warn about \n in tooltips like ('aes(tooltip) does not support line breaks; please remove \n from aes(tooltip)') on the R side to avoid TSV corruption.

Could you advise which approach we should go with?

[tdhock]

Thanks for investigating!
rendering with a space instead of a newline is preferable to not rendering anything at all.
but even in that case, it would be good to add a warning("newline detected in geom_text label, which will be converted to a space; please use multiple text elements at different y positions instead") or similar.
Can you please try changing all three fwrite/write.table calls to fwrite()? The default quote="auto" should work (only adding quotes where they are necessary).

[tdhock]

You mentioned that converting \n to <br/> may be a possibility... if that works that would be preferable, so can you try that please? (I'm not sure if it would work though)

[codecov]

Codecov Report

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[suhaani-agarwal]

the tooltips now support \n

for example the following code:

viz<-list(
  p1=ggplot()+
    geom_point(aes(
      x, x, tooltip=x, color=x),
      size=5,
      data.frame(x=c("one line", "two\nlines", "three\nlines\nhere")))
)
animint2dir(viz, "label-aligned")

produces

Screen.Recording.2025-09-03.at.2.05.23.PM.mov

[tdhock]

great thanks! please increase version number and add an item to NEWS and then I will merge.

[tdhock]

if we do this on R instead of in JS, I think we shold be able to get line breaks in legend entries too, see test below.

maybe also desirable in

• axes titles
• axes tick marks
• facet titles
• geom_text label

but all of these features are too much for this PR, so I will create a new issue.

[tdhock]

great thanks!