But, more importantly, the amount of cycles that would be needed to text-wrap most websites is effectively zero. Most websites are simply not typesetting the volumes of text that would be needed for this to be a concern.
Happy to be shown I'm flat wrong on that. What sites are you envisioning this will take a lot of time for?
I've measured this, and no, it's not. What you're missing is the complexities of typesetting Unicode and OpenType, where GSUB/GPOS tables, bidi, ruby text, etc. combine to make typesetting quite complex and expensive. HarfBuzz is 290,000 lines of code for a reason. Typesetting Latin-only text in Times New Roman is quick, sure, but that doesn't cut it nowadays.
I would wager you can find scenarios where it is a large number. My question is if there are sites people use?
Seriously taken, these would all be reasons not to do many of the things Unicode does. And yet here we are.
That all said, if you have measurements, please share. Happy to be proven wrong.
- handling shy hyphens/hyphenation when splitting long words -- working out where to hyphenate so it is readable, then how that affects the available space takes time to compute to ensure that justified text doesn't result in large blocks of whitespace esp. for long words;
- handing text effects like making the first letter large, or the first word(s) larger, like is done in various books;
- reflow due to any changes resulting from text rendering/formatting (e.g. if applying kerning or hyphenation results in/does not result in text wrapping);
- impact of things like kerning and digraphs (e.g. ffi) on text width -- including determining if a word can be split in the middle of one of these or not;
- combining characters, emoji (with zero-width non-joiners), flag Unicode character pairs (including determining valid pairs to determine if/where to split on), etc.;
- mixed direction text (left to right and right to left) handling and positioning;
- the mentioned Ruby text (e.g. https://www.w3.org/International/articles/ruby/styling.en.ht...) -- dealing with both the main text wrapping and the above/below text wrapping, both of which could happen;
- for Chinese/Japanese/Korean ensuring that characters within a word don't have extra space, as those languages don't use spacing to delimit words;
- other things affecting line height such as sub/super script text (mathematical equations, chemical symbols, references, etc.).
Like, I am largely aware that it is a hard problem. So is just rendering text, at large. The added difficulty for justifying text is still not something I expect to impact the vast majority of sites. If you are willing to break your content into multiple pages, I hazard it isn't a significant chunk of time for most content.
Are there edge cases? Absolutely! Most of these are isolated in impact, though. And I do think a focus on whole content optimization is clouding a lot of people's view here. You are not doing yourself any favor by optimizing a full book every time a chapter changes.
There is also the idea that you have to find the absolute best answer for justifying text. Why? One that is low enough on a penalty score is just fine. Akin to the difficulty in finding all tilings of a board, versus just finding a single tiling for a board. Or a single solution to the N-Queens question, versus all solutions. If you just want a single solution, you don't need the raw compute necessary to get them all.
I hardly can open any website w/o some anti-bot check burning my CPU to the ground for 1/2 minute or something (if it doesn't manage to entirely crash my Firefox in the process like cloudflare). I rather would wait for 0.2s text wrapping than that, that's for sure. :)
Try zooming in and out with text-wrap: pretty vs text-wrap: wrap
Are there ereaders that have to typeset the entire text of what you are reading? What is the advantage of making the task harder?
Still, I should acknowledge you provided an example. It surprises me.
As often as the font size changes.
Even the few times I do change text size on my e-readers are largely mistakes. Having gestures to resize is frustrating, in the extreme.
When I'm home, I read books.
Can't speak to Apple Books, but at least Pages.app (and iWork in general) use a separate text engine from TextKit, focused on higher fidelity at the cost of performance -- optical kerning, etc. (Terminal.app also does not use TextKit.)
OpenStep used Display Postscript and was written in Objective-C; WebKit is written in C++.
Rendering text on the web is a different animal all together.
Again, I won't claim it is absolutely free. It is almost certainly negligible in terms of processing power involved with any of the things we are talking about.