Incorrect guide positions when font changes on parsed line

[Xenovore]

This appears to only parse a single line (the top line - 2?) to determine the indentation positions for the entire text editor view. But if the font is different in the parsed line, it will result in all the indent guides being at incorrect positions. In particular, this will happen when using extensions like Better Comments that allow the font to be customized for comments.

Suggestions: Check if the line is commented? Check if font on the parsed line is different and/or mono-spaced? Parse more than one line and use the majority indent widths?

[zooba]

For reference, the code that does this detection is here:

indentguide/src/Guides/IndentGuide.cs

Lines 268 to 270 in 86691b5

	double spaceWidth = firstVisibleLine.VirtualSpaceWidth;
	if (spaceWidth <= 0.0) return;
	double horizontalOffset = firstVisibleLine.TextLeft;

Replace that with a better calculation and set the same two variables and it should Just Work. The trick is that we don't really want to trigger VS to load text lines that it isn't already loading - hence the use of visible lines.

I'm also not going to assume that any particular character indicates a comment, because this ought to work with all of #, //, /*, rem , ;, ', ''', """ and any others without having to detect the language. Maybe skipping ahead to the first line that would have a line displayed and using its width makes the most sense? But if you've got variable width indents, you're ultimately going to be in trouble with this kind of extension.