Jumping cursors

Mark Waddingham mark at livecode.com
Thu Jan 5 10:19:40 CET 2017

On 2017-01-05 09:56, Richmond Mathewson wrote:
> Um: this could be a "stupid Richmond" case rather than anything else
> as I populated cells FF001
> to FF01E with Grantha Samyuktaksharas: and those in FF002 and so on
> behave perfectly well;

This is a case of 'stupid engine', rather than 'stupid Richmond':


The implementation of the bidi algorithm in the engine is currently 
computing surrogate pairs incorrectly. In this case, 0xFF001 is being 
read as a character in the arabic script area in the BMP which has the 
'Arabic RTL' attribute. This means that it is being treated as an RTL 
character when it should not be.

> but FF001 could be a non-character which I had overlooked: If one goes 
> here:
> http://www.unicode.org/charts/PDF/UF0000.pdf
> information regarding FF001 is not much use . . .
> The Range: F0000 - FFFFF is the Unicode Supplementary Private Use
> Area-A; a bit like that area
> in New Mexico.
> Although "The entire plane is dedicated to private use with the
> exception of the last two code points."
> would seem to imply that FF001 should cause me no problems.

Indeed - end user applications are free to use SPUA-A and SPUA-B for 
whatever purpose they wish... With the only caveat that two uses of said 
areas might be completely incompatible. (i.e. a font designed for use in 
one application which uses these areas, might break horribly in an app 
which uses the area for a completely different purpose).

Warmest Regards,


Mark Waddingham ~ mark at livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps

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