Feature request: Set style on range

[mcclure]

Hello, I am interested in using tui-textarea. However I have a need. For my application, it must be possible to apply a style to a range of text. For example, maybe I am implementing syntax highlighting in a programming language. Or maybe I am implementing a spell checker and I want misspelled words to be highlighted. Or maybe I want the word under the cursor to always highlight.

Is this possible? Reading the docs, tui-textarea currently there is styling for specific special items known to tui-textarea, such as the search highlight or the cursor or the selection. But it seems like I cannot just say "highlight characters 4 through 7 on line 5". (Ideally, my custom "range" highlight should combine with the existing style types intelligently— for example if I set characters 4-7 as red, and the cursor character as an underline, and I move the cursor to position 5, that character should be red and underlined).

There is already a feature request for syntax highlighting. But I think this is a different request, simpler and more basic. Syntax highlighting controlled by tui-textarea would not allow me to style special ranges of text with meaning known only to my application.

[mcclure]

This feature is a must-have for my application (I need at least two additional highlight ranges beyond what base TextArea offers) so I am trying to prototype it… I'm doing this via an extra_highlights: Vec<(usize, usize, usize, Style)> /* line_idx, from_char, to_char, style */ which is a member of TextArea and gets passed down into LineHighlighter.

I am getting tripped up because I do not quite understand what the Boundary/Span system is or how it works. Gonna just type out what I think is happening:

• A boundary is a highlight kind (from an enum) plus a position. A span is a style plus a string to display.
• Each of the bespoke highlight types (cursor, select, search) are added to a list.
• The list is sorted.
• The list is traversed, creating a stack of active highlights, as you go you snarf text off the line and put it plus the appropriate style into the span list.

This makes sense, what I don't get is:

• I don't understand how you handle endings. One of the boundary types is "End". Okay, so you hit an end and you pop a layer off the stack. Fine. But what if the boundaries have non-stacklike behavior? For example I could imagine a line that looks like

Jack[selection begins]daws lo[search begins]ve my bi[selection ends]g sphinx of qua[search ends]rtz.

I haven't yet found where/how this case is handled.

I will look at it closer tomorrow but any guidance appreciated!

[mcclure]

Actually, maybe I don't need to understand how it works. I just added my boundaries to LineHighlighter and it seems to work. I will likely drop a first-pass PR soon. I am still curious what happens if I set "overlapping" ranges (as in my sphinx example above) however.