If a simple Array is used to hold lines of text, whenever a line is edited, the array will need to be sliced, lines modified, then put back together again. It works fine up to a limit at which point the editor becomes noticeably unresponsive. I scratched my head over this one for a while, thinking …

Thanks, I never heard of a Gap buffer before, but that looks very close to what I am implementing, its just that I have the ‘gap’ as a separate item being the focus of the zipper. There was also a link to the ‘rope’ structure apparently used by emacs: https://en.wikipedia.org/wiki/Rope_(data_struct…

I pushed a demo up here: [image] Scroll Bar Spike This is using my gap buffer implementation to hold the text. When the cursor is moved with up/down arrows or page up/down, the zipper focus is shifted to the line where the cursor is - so the underlying arrays are…

I did a little work today to optimize the re-zipping of the buffer when the focus moves. Even on the 1M line file, the performance is not bad, just the occasional blip as the garbage collector runs. [image] Scroll Bar Spike Bear in mind that in a real editor I wo…

Still a little work to do around getting the cursor to behave nicely when wrapping around line ends but - I have now added a basic editing capability to the demo. Delete and Backspace work as expected and you can enter text. This is all done through capturing onKeydown events. Input through a hidde…

Cursor movement now improved, home/end work, it wraps lines, maintains a target column when moving around beyond the line end and so on. [image] Buffer Spike

[image] rupert: One problem that I have not figured out yet, is what to do when the lexer has state? So in an editor you can enter a single double quote mark " and if the language you are working with has strings, you might see all subsequent lines of text turn a different color - they were code…

So I jumped in an implemented the quoted/non-quoted lexer for syntax highlighting, rather than something stateless. This will help me test the pathological case which is the user entering " on the first line, then Ctrl+End to jump to the end of the file. Current implementation is using a 500 line f…

Got all this rippling stuff working now. :boom: [image] Buffer Spike You can test the pathalogical case by entering a single " on the first line and then CTRL+End to jump to the end of the file. This must ripple down the entire file, so you can see it takes a lit…

Efficient Text Editing Buffer

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MarkHamburg October 20, 2020, 5:23am 2

See also https://en.wikipedia.org/wiki/Gap_buffer though not quite on point within a pure language.

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Efficient Text Editing Buffer

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