How to get height or width of content and layout in Typst as a length type?

Question

How to get widths of content and layout as a number (length type in Typst).

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What I tried is to use layout() and measure() as suggested by Typst doc. Using these functions, I can show the width, for example 453.54pt, on the pdf file, but the data type of 453.54pt is content, and I cannot convert it to length type.

More specifically, I tried the following code:

#let layoutwidth = layout(size => {return size.width})
#let textwidthof(body) = context { return measure(body).width} // a function
#let atextwidth = textwidthof[Hello World]

Although we can print the two widths layoutwidth and atextwidth on the pdf file, it is of type content, not length. I also tried to convert it to string str() and then eval(), but it does not work! Any ideas?

Answer 1

I've been facing the exact same problem today, and finally found that it's due to the context.

In the measure doc page they say it has to be used in a given context because it depends on where it is in the document.

The thing is you have to be in a context to access the fields of width and height :

#let authors = ("John One", "John Two", "John Three")
#let org = "University"

#let auths = text(style: "italic")[#authors.join(", ")]

#context {
    let authsize = measure(auths).width
    let orgsize = measure(org).width
    set page(
        footer: [
            #text(size: 11pt)[#auths] #h(100% -authsize -orgsize -1pt) #text(style: "italic")[#org]
        ]
    )
}

However this would not work because the variable only exist in the context :

#context {
    let authsize = measure(auths).width
    let orgsize = measure(org).width
}

#set page(
    footer: [
        #text(size: 11pt)[#auths] #h(100% -authsize -orgsize -1pt) #text(style: "italic")[#org]
    ]
)

And the following is what returns a content that we can't use, I'm not sure of the reason but I would guess that the content type comes from the context keyword :

#let authsize = context measure(auths).width
#let orgsize = context measure(org).width

#set page(
    footer: [
        #text(size: 11pt)[#auths] #h(100% -authsize -orgsize -1pt) #text(style: "italic")[#org]
    ]
)

Edit : If the goal is to spread text across the page, it's better to use fr instead of context and measure.

footer: [
    #text(size: 11pt)[#auths] #h(1fr) #text(style: "italic")[#org]
]