string-pixel-width | Blazingly fast measure string width in pixels | Runtime Evironment library

I've been implementing a chat client in Electron (Chrome) and React. Our top priority is speed. It behooves us, then, to use a virtualized list component (also known as "buffered render" or "window render"). We've explored react-virtualized, react-window, and react-infinite, among others.

One issue all these components have in common is that if supporting list elements of variable heights, the heights need to be known in advance. Now, some chats are very long, and others are very short, so that presents a challenge for us. (Images and video are easy thanks to EXIF data and ffprobe).

So, we're faced with the challenge of measuring heights while also straining to be extremely performant. One obvious technique is to put the elements in a browser container off-viewport, perform the measurements, and then render the list. But that hurts us on the performance requirement aspect. Software like react-virtualized/CellMeasurer (which is no longer maintained by the original author) and react-window make us of this technique, built in to the library, but performance is somewhat slow as well as unreliable. A similar idea that might be more performant would be to use a background Electron Browser window to do the rendering and measuring, but my intuition is that wouldn't be that much faster.

I submit that there must be some solved way to figure out string height in advance, according to word wrap, max width, and font rules.

My current idea is to use a library like string-pixel-width in order to calculate row heights as soon as we get the text data through our API. Basically, the library uses this piece of code to generate a map of character widths [*]. Then, once we know how wide each text, we separate each line when it maxes out the computed max row width, and finally infer list element height through row count. It's going to require a little bit of algorithmic fiddling due to break-word but there are libraries to help with that – css-line-break seems promising.

[*] We would have to modify it a bit to account for all Unicode character ranges, but that is trivial.

Some options I haven't fully explored yet include the python weasyprint project and the facebook-yoga project. I'm open to your ideas!