Fix #1041: Wrap long lines based on a settable maximum line width

[hwoongkang]

Previously, rendering glyphs in the scene depended solely on glyphLines property, which originates from text entry of side panel.

And I recognized that to handle alignments, advance width of glyphs and total line lengths were already being tracked.

By using stack and pushing the "remaining line" on the top of the stack when the line length exceeds certain threshold, it was possible to implement the line wrapping algorithm.

--

But the problem is that currently "selection API" depends on "indices", and various codes accessing the current selected glyphs use these line and glyph indices to get glyph info out of glyphLines property.

This leads to a bug:

• the text I used is:

abcdeabcdeabcdeabcdeabcdeabcde
cdefg

• it gets wrapped as:

abcdeabcdeabcdeabcde
abcdeabcde
cdefg

when I select b from the "wrapped second line", and edit it, d gets edited because it is the second glyph of the second line, with respect to glyphLines

Therefore I handled this case by changing related codes to use positionedLines instead of glyphLines. Since type signatures of two data differs, some transforming is done. This is what second commit is about.

But it feels too much "ad hoc" for me, so any suggestions or reviews will be very helpful

[justvanrossum]

Thank you for your proposal. I see the problem with the indices, but I will have to think more how to resolve it.

[justvanrossum]

Sorry for letting this sit for so long.

I think the right solution requires more work: the selection should not be a lineIndex/glyphIndex duo, but a single index into the full input string (where a newline is simply a character). We then need an efficient way to find the selected positionedGlyph in the positionedLines, and also the reverse, taking dynamic line breaking into account.