egui_richedit

Rich-text editing for egui, over paragraphs your application lays out and draws itself.

egui's TextEdit edits one string in one format. A document editor draws paragraphs of styled runs among lists, tables and pictures, and wants a caret that moves through all of them as if the page were one surface: click anywhere and type, Enter splits a paragraph, Backspace at its start joins it to the one before, the arrows cross from one paragraph into the next, and a selection can run across several. This crate is that caret. It owns no document and no layout. Your application keeps both, and the crate asks it for two things:

• A description of each paragraph's text as it lays it out, built with ParagraphJob. Most text is appended with text. Anything drawn differently from what your document holds (a tab drawn as spaces, a footnote citation your document does not count as text, a field showing its value) is appended with atom, and the caret steps over it whole.
• An implementation of Model over your document: a paragraph's text, the paragraphs before and after it, and applying an Edit (replace a range, which may span a paragraph break, or split a paragraph). The editor tells the model when an edit begins a new undo step, so a run of typing is undone in one piece and your own undo keeps working.

In return, RichEdit handles keys, the pointer, the clipboard and input-method commits, and paints the selection and the blinking caret over your galleys.

Using it

Each frame, call RichEdit::input before anything is laid out, so the layout that follows already shows what was typed. Then, for every editable paragraph in document order, whether or not it is on screen:

1. Build its ParagraphJob.
2. Lay it out with egui.
3. Allocate a response that senses clicks and drags.
4. Hand the galley, the job's offset map and where you placed it to RichEdit::paragraph, which paints the paragraph.

The editor finds its way up and down through where each paragraph was drawn, so paragraphs scrolled off screen are reported too.

examples/notes.rs is a complete window over a list of strings:

cargo run -p egui_richedit --example notes

Positions

A Position is a paragraph, named however your model likes, and a character offset into your model's text of it. Offsets count characters, not bytes. They count your document's text, not what is drawn; the offset map built by ParagraphJob translates between the two.

License

MIT.