RFR: 8330559: Trailing space not rendering correctly in TextFlow in RTL mode [v2]

[John Hendrikx]

On Thu, 6 Jun 2024 15:35:07 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

>> CTGlyphLayout is not common code. It is mac only (so no need to mention mac)
>
> I see, PrismFontFactory:164 getNativeFactoryName().
> It would be nice to place platform-specific code in a package bearing the platform name, or at least mention this in a class-level comment, but I guess it's too late.
> 
> It means the scope is already limited to macOS, we are good.

I'm having some doubts about the solution still.  It is mentioned that this problem can occur in text containing both LTR and RTL text together, however, as far as I can see, a `TextRun` never contains a mix of text directions.  Can you clarify this?

Also in RTL text, I'm guessing "trailing" spaces are in fact what we call leading spaces in LTR text, ie. trailing spaces in a RTL text sample would be: `  قطة`

I'm guessing that CT (Core Text) returns the positions of all the trailing spaces as negative values, not just the first, and the first glyph (seen from the left) with an offset of 0.  Since the CT framework can also handle alignments, but FX is not making use of this, I think all calculations are done with the standard left alignment. It would make sense for spaces that "fall off" the left end (because they're "trailing") to have negative values.  Similarly, if you did LTR text for `cat  ` with a right alignment, all glyphs would have negative values, except the two trailing spaces that would have positive values.

So I'm curious to see what happens if you have more than one trailing space (eg. `     قطة`) and what `CTRunGetPositions` returns then.

-------------

PR Review Comment: https://git.openjdk.org/jfx/pull/1468#discussion_r1630186928