Alignment of 「 is left instead of right

[ElvenSpellmaker]

In mintty the alignment of the 「 character seems to be to the very left of the cell in every font, but in other programmes this isn't the case and it's at the right of the cell:

mintty:

Word:

In this issue:

In Powershell ISE (shows as ? boxes in normal powershell):

Note: PS seems to treat it as single width, are the characters ambiguous width? Unless it's combining with the next char 🤔?

[mintty]

U+300C LEFT CORNER BRACKET is a Unicode wide (not ambiguous-width) character. It should be centered within 2 character cells by the font already. I had noticed before that some wide characters have this unpleasant effect and I guess it's a font issue.

[mintty]

It could be a combined effect with the Windows font fallback mechanism, i.e. the character may not be included in the selected font and then taken from another font.
Mintty has a mechanism already to expand a character glyph to the required character cell width, however it must be used with care, in order to avoid expanding wide glyphs again as once occurred (#570). An experimental workaround patch to include the two corner brackets in this mechanism works fine but we'll need to find a sustainable criteria which characters to cover by this expansion.

[mintty]

Actually, the Windows function to determine the glyph width does not seem to work in the font fallback case, so for a reliable workaround, we would need to measure the real rendered glyph width. This mechanism is also already available in mintty for some special situations (now applied to ambiguous-width characters, using a cache to tame the performance penalty).

[mintty]

With the current version, matching CJK brackets are expanded if both are too narrow.
(Alternatively, it could be considered to right-align the left bracket.)

[mintty]

Released 2.8.5.