Is it possible to style only what's needed for the visible page? #734

Aside, I have a problem I don’t know how to understand. With long files, scrolling is slow, even when no colorization is involved. Scrolling line by line with the arrow-down key always pressed, at the beginning of the file if is fast as usual, then as the line position increases, it become more en more slow. It start to be perceptible at about line 1300. It must be related to the custom colorizer, because it does not happen without it (ex. if I change the buffer’s language to another one not using this colorizer). But it does not even listen for this kind of event and I checked colorization does not occurs during that. It’s mysterious.

It happens even when the colorizer is replaced with just this:

events.connect(events.STYLE_NEEDED, function(end_pos, buffer)
   if end_pos >= 1 and buffer ~= nil then
      buffer:start_styling(1, 0)
      buffer:set_styling(end_pos - 1, view.STYLE_DEFAULT)
      return true  -- Anything not nil
   end
end, 1)

That’s very strange. May be something is missing. Some finalization?

Edit: investigated as much as I could and opened a discussion about this different topic: #735

May be this is for folding. Colorization could be done for only the visible area, but the same is not true with folding. Because folding change the number of lines in the complete view of the document. Ex. if folding is not calculated up to the end of the document, there is no way to tell what is the line number of the end of the document and jumping to it with Ctrl+End would not be possible.

Separating colorization and folding would require too much change, I guess.

What I’m looking for, can be OK only for people not using folding (I never use it).

It is done when spell-checking. The file modules/spellcheck/init.lua, at line https://github.com/orbitalquark/textadept-spellcheck/blob/ad150369ade366a9d492626f1b07c57829dab659/init.lua#L205 , contains this:

buffer:colorize(buffer.end_styled, buffer.line_end_position[next_page])

Scintilla tells clients when it needs styling and folding via the STYLE_NEEDED event. Textadept has no control over this. However, the view.idle_styling (https://orbitalquark.github.io/textadept/api.html#view.idle_styling) option allows you some level of control. If you choose view.IDLESTYLING_NONE, then Textadept should only style the visible text. By default Textadept styles the rest of the buffer during idle time.

Just tested view.idle_styling = view.IDLESTYLING_NONE and it’s all fine. Now editing at the start or at the end of a big file, is equally responsive (while still a bit too slow to be said perfectly responsive). It’s even faster when colorizing the whole document, because doing Ctrl+End from the top of the document, triggers colorizing the whole in a single request instead of with multiple requests and it is about five times faster.