On Fri, Sep 3, 2010 at 4:25 PM, Eli Zaretskii <[email protected]> wrote:

<- Snipped text ->


> Even if everything I said above is correct, there are complications.
> ABCDE could be inside an embedding with left to right override, like
> this:
>
>  foobar RLO ABCDE PDF
>
> This should be displayed as
>
>  foobar ABCDE
>
> i.e., "ABCDE" is not reordered, but displayed in the logical order, as
> forced by RLO.  Therefore, the reshaped "XYZ" should also be displayed
> left to right:
>
>  foobar XYZ
>
> But, if I understand correctly how composition works, the
> auto-composed sequence in this case will still be just "XYZ", without
> the RLO and PDF control characters.  So the `shape' method of the font
> driver will still see just "XYZ" in the LGSTRING, without the control
> characters, and will reorder "XYZ", which is incorrect.
>
> If we need the `shape' method to reorder glyphs, then in order for it
> do its job correctly, we need to give it the entire bidi context of
> the string we are asking it to reshape.  In the above example, we need
> to tell it about the override directive, i.e. pass it "ABCDE" with
> surrounding RLO and PDF controls.  This flies in the face of the
> current design, which separates reordering from glyph shaping.
>
>
Is that a typo? I think you mean LRO (U+202D) rather than RLO in all cases
above.
(Just commenting, to avoid further misunderstandings).

   Amit
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