Avoid drawing hidden text in DocView:draw_line_text

[Guldoman]

With this PR, we no longer send hidden (tokenized) text to the renderer.

Non tokenized text or text tokenized as long strings is still a problem, which can be solved by splitting the tokenized text into smaller pieces.

Here there might be a performance impact caused by having to call font:get_width, but this needs testing.

[jgmdev]

Does this means ability to open a file with really long lines and not having the editor choke?

[Guldoman]

It surely helps, but only on lines where the tokens aren't extremely long.
We should split very long tokens in the tokenizer for those cases (like plaintext).

[adamharrison]

As discussed on discord:

It is probably better to do a quick clip check in the rencache for the first bit, to avoid the double width computation; also has the added benefit of just generally probably slimming down the rencache. We should know the current clip in C at the time of sending the command, so I can't think of a reason why that wouldn't work.

[Guldoman]

Thanks to Adam's suggestions:

• Removed the Lua check to avoid sending the draw commands for strings "to the left" of the DocView as it's done on the C side (and also avoids the font:get_width issue). It now just stops early.
• Tightened the check done when adding draw commands to exclude the commands that would fall outside the latest clip. It was previously done only on the window rect, so this should skip a few more draw commands.

[adamharrison]

Looks good. Tested, and works fine. Still chokes on large files, but as you say, almost assuredly better, and don't see any rendering errors. Merging.