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Text Editor Data Structures

cdacamar.github.io

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Re: Text Editor Data Structures

#41

Post by b33j0r »

badsectoracula wrote: post #17
b33j0r wrote: post #14

Earlier quoted context omitted.

I might have a way to simplify this? A plaintext document is an array of chars, a richtext document is tree, which may or may not be well-formed. Think about someone trying to bold semi-half of_a sentence_, and how MS Frontpage was made by smart people, it’s just really hard. The most interesting thing lately is the HTML attribute `contenteditable`, and how it almost just kinda works! You still have to be full-stack…

Yeah, that trying to bold half of a sentence - or even better, the middle of a sentence - is why i was wondering about simpler alternatives to DOM. Some time ago i toyed around with an HTML editor[0] (that one had to use a DOM anyway, but my question is for rich text editing in general - BTW the rectangles in the shot show a selection that goes across nodes) and doing something like that involved traversing all the n…

Nice. I’ve searched far and wide, and most people still end up starting a whole company that only does a text editor.

Quill works but is basically dead since 2017. Almost anything foss is in a similarly ambiguous boat.

And then people like us, defeated, eventually buy something when we actually need it.

There are just so many ways that users try to use it. It’s a tough problem!

Re: Text Editor Data Structures

#42

Post by WorldMaker »

rcoveson wrote: post #34
WorldMaker wrote: post #30

Earlier quoted context omitted.

Some "single character" emoji easily exceed 5 bytes in all encodings. You may think ZWJ sequences are cheating, but emoji isn't the only language encoded in Unicode with complex ZWJ sequences.

My question is about the phrase up to 5 . What in Unicode is up to 5? Codepoints are up to 4 in all the encodings I know. ZWJ sequences may as well be arbitrarily long. What is "up to 5"?

I read this as colloquial English for "around" or "approximately". Not setting a bound limit, but setting an example size.

Re: Text Editor Data Structures

#43

Post by eludwig »

badsectoracula wrote: post #5

There are tons of articles about plain text editor data structures, but what about rich text editor data structures? Let's say i want to implement a text editor that can have bold, italic, underline, etc text but also be able to do automatic word breaking, align paragraph text to left/middle/right, insert images and/or other objects, have floating images and/or other objects around which the other (non floating) text…

Many older word processors (the only ones I'm familiar with) used style "runs", which are simply an array of structs that contain startPosition, endPosition (or length) and then a bunch of style info in whatever way makes sense to them.

I worked on Ready,Set,Go! back in the day and also wrote my own styled editor for the Mac in the 90's.

One interesting thing about this is that you could use a lazy "adjustor" to remove duplicate or overlapping styles. No need to worry about it during typing or selecting. A low priority task could analyze the runs and fix them up as needed and no one was the wiser.

IMO, the hardest part about writing a word processor back then was font management. You had to construct width tables to be able to compose lines properly. This generally involved a bunch of poorly documented APIs and peering into opaque data structures.

Re: Text Editor Data Structures

#44

Post by rcoveson »

cstrahan wrote: post #40
rcoveson wrote: post #34

Earlier quoted context omitted.

My question is about the phrase up to 5 . What in Unicode is up to 5? Codepoints are up to 4 in all the encodings I know. ZWJ sequences may as well be arbitrarily long. What is "up to 5"?

The original quote for reference: > So one Unicode character can be up to 5 bytes long and take up the same canvas space as 3 characters. FWIW, I didn't read that as suggesting an upper bound of 5 bytes, but rather as an example using arbitrary numbers: N bytes of code units could, depending on the font providing the glyph(s) for the respective grapheme(s), could be rendered at M times the size of, say, the letter A,…

Continue to the next sentence of context:

> You also need to read ahead as there are combination characters, for example a smiley combined with the color brow becomes a brown smiley.

Emphasis mine. Clearly combination characters are being treated separately.

Frankly I think it's crazy to read "up to 5 bytes" and not think that it suggest an upper bound. I think you're reaching for a highly questionably interpretation of a totally unambiguous clause. If the author meant to express what you're saying, they would certainly have written: "Some Unicode characters are 5 bytes long and take up the same canvas space as 3 characters". Which would still look incorrect if they followed it with the sentence "You also need to read ahead as there are combination characters...".

It is far more likely that the author is simply mistaken and should have said 4 bytes, and perhaps used the word "codepoint" instead of "character" in the original sentence. That's a perfectly understandable technical error, while the reinterpretation you're putting together would imply an error of colloquial language.

Re: Text Editor Data Structures

#46

Post by vbezhenar »

Can someone point me to structures/algorithms to use for text editor which could support files of unlimited lengths (including lines of unlimited length) without loading those fully in the buffer?

I miss that editor so much, that I'm considering to write one some day, but I have no idea how to do so. I can invent things myself, but I guess those things were invented already back in the days computers were different.

Re: Text Editor Data Structures

#47

Post by rcoveson »

WorldMaker wrote: post #42
rcoveson wrote: post #34

Earlier quoted context omitted.

My question is about the phrase up to 5 . What in Unicode is up to 5? Codepoints are up to 4 in all the encodings I know. ZWJ sequences may as well be arbitrarily long. What is "up to 5"?

I read this as colloquial English for "around" or "approximately". Not setting a bound limit, but setting an example size.

But you also read it as referring to ZWJ sequences? So the author has picked a number that is actually below average and they've worded it as up to...?

Saying a ZWJ sequence can be "up to 5 bytes" is like saying "the current generation of Intel processors run at clock speeds of up to 2 GHz".

If they were referring to ZWJ sequences (I don't think they were; I think they were just misremembering the maximum encoded length of a codepoint) and they had said "up to 35 bytes", then I might agree with you. It's still not technically accurate, but it's a reasonable colloquial usage, like saying "human males can grow up to seven feet tall".

Re: Text Editor Data Structures

#48

Post by egonschiele »

I've been wondering if there's a good algorithm to handle highlights in a piece of text. If I highlight some text, lets say the part between the => "Idioteque" is a song => by the English rock band Radiohead If I want to then edit this text, is there an efficient algorithm for figuring out the start and end index of the highlight for the edited text?

Re: Text Editor Data Structures

#49

Post by thaliaarchi »

starfreakclone wrote: post #38
nsajko wrote: post #33

This seems revisionist/ignorant. The article attributes a "piece tree" data structure to VS Code developers, however the must-read 1998 paper by Charles Crowley, Data Structures for Text Sequences , already mentions search trees as being used to enhance the naive piece table in some text editors. https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.48...

Thank you for the pointer! I was actually not aware of this paper at all, which is why it was not included here (not sure how I missed it). I'll be sure to push a revision to the blog which mentions this paper.

You may also want to take a look at “Deletion: The curse of the red-black tree” (Germane and Might 2014), which presents functional deletion for red-black trees.

https://matt.might.net/papers/germane2014deletion.pdf

Re: Text Editor Data Structures

#50

Post by WorldMaker »

rcoveson wrote: post #47
WorldMaker wrote: post #42

Earlier quoted context omitted.

I read this as colloquial English for "around" or "approximately". Not setting a bound limit, but setting an example size.

But you also read it as referring to ZWJ sequences? So the author has picked a number that is actually below average and they've worded it as up to... ? Saying a ZWJ sequence can be "up to 5 bytes" is like saying "the current generation of Intel processors run at clock speeds of up to 2 GHz". If they were referring to ZWJ sequences (I don't think they were; I think they were just misremembering the maximum encoded le…

I think you are trying to read something that wasn't meant to be technical documentation as if it was trying to be exact technical specifications. I'm not the original author, so I don't have reason to litigate this any further, and I'm not sure what you are arguing about at this point.
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