Caption for WAV display

[rmsrosa]

Hi,

For my notebooks, I added a composite type similar to WAVArray which adds a "caption" field, which is then used in show to display a caption in an html figure element wrapping the html audio controls.

Ideally, it should replace the existing WAVArray, but that could be a breaking change, so I made it into a new struct CWAVArray, also for the lack of a better name.

It doesn't look well in the same cell as WAVArray, due to the identation, but one can use CWAVArray with the empty string if no caption is desired.

If you like the idea, I could make a PR with the above. Let me know.

This is essentially it:

struct CWAVArray{T,N}
    Fs::Number
    data::AbstractArray{T,N}
    caption::AbstractString
end

CWAVArray(Fs::Number, data::AbstractArray) = CWAVArray(Fs, data, "")

wavwrite(x::CWAVArray, io::IO) = wavwrite(x.data, io; Fs=x.Fs)

function show(io::IO, ::MIME"text/html", x::CWAVArray)
    buf = IOBuffer()
    wavwrite(x, buf)
    data = base64encode(String(take!(copy(buf))))
    markup = """<figure>
                $(ifelse(x.caption !== "", "<figcaption>$(x.caption)</figcaption>", ""))
                <audio controls="controls" {autoplay}>
                <source src="data:audio/wav;base64,$data" type="audio/wav" />
                Your browser does not support the audio element.
                </audio>
                </figure>"""
    print(io, markup)
end

And here is how it displays in a jupyter notebook, including the case with an empty caption:

[dancasimiro]

@rmsrosa This looks like a nice addition. Could you help me understand why you cannot extend the existing WAVArray type? I'm probably missing some obvious detail, but it seems like this functionality could be added without breaking the API.

[rmsrosa]

Yeah, I guess it doesn't break it. It adds a field, but it should be fine with the constructor that only takes the first two fields.

Should I make a PR?

[dancasimiro]

Yeah, I guess it doesn't break it. It adds a field, but it should be fine with the constructor that only takes the first two fields.

Should I make a PR?

Yes, please! A PR would be very much appreciated.