TextMetrics support

[Fabio Donzella]

Hi everyone,

there's any chance to know if and when TextMetrics APIs (https://developer.mozilla.org/en-US/docs/Web/API/TextMetrics) will be not experimental anymore? Will they become standard or not?

I'm writing production code for future releases and I'd like to know if I can use these APIs or not! Thanks in advance!

[Koji Ishii]

Hi Fabio, thanks for the question. Which properties are you interested in?

We're shipping following properties:

    actualBoundingBoxAscent
    actualBoundingBoxDescent
    actualBoundingBoxLeft
    actualBoundingBoxRight
    width

We will be shipping following properties in M87 (tracking crbug.com/1129621):

    fontBoundingBoxAscent
    fontBoundingBoxDescent

These properties expose platform-dependent values. We're also shipping the following 3 descriptors to make it interoperable across platforms in M87 (tracking crbug.com/1098355):

    ascent-override
    descent-override
    line-gap-override

https://www.w3.org/TR/css-fonts-4/#font-metrics-override-desc

We're considering other properties too, but they have some technical issues to be resolved. It'd help us to learn which properties you need.

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[Fabio Donzella]

Hi Koji, thanks for your reply.

Let me briefly explain what I'm doing: I'm porting an old graphic engine windows based to a Web App using HTML5 Canvas and WebAssembly. I'm facing a lot of issues to replicate the original behaviour with texts (fonts especially), that's because the original rendering done by GDI is different, depending on the font. I know that the 100% precision is almost impossible, but at least I want to reach as much as possible that percentage without binding to any O.S. in particular

What I need is exactly fontBoundingBoxAscent/ fontBoundingBoxDescent, actualBounding is depending on the string drawn on the Canvas and so it would not provide an homogeneus approach. Maybe I can avoid other properties like ascent, descents ecc. for now.

Considering that the code I'm actually writing will be part of a system that will remain in production for many years, I'm particularly interested in security, reliability and robustness: so I'm happy to hear that this will come out very soon, but in general these TextMetrics API are an experimental technology and I want some insurances that these features will not be dropped in a near future or any other limitation that can cause me some problems

Thanks in advance for your help,
Fabio