Input: <L1><RLO><NSM><L2><L3><PDF><L4> output: <L1.l><L3.r><L2.r><NSM.r><L4.l> How to render? You say «L3. Combining marks applied to a right-to-left base character will at this point precede their base character. If the rendering engine expects them to follow the base characters in the final display process, then the ordering of the marks and the base character must be reversed». Not that case. «Defective combining character sequences should be rendered as if they had a no-break space as a base character». Aha! Beautiful. What for to use the default ignorable codepoints as the base for the NSM?
<html> <body> <p> a‮́bc‬d </p> <p> a‮́bćdé‬fg </p> </body> </html> It is acbd áed́cbfg or maybe acb́d áed́cb́fg It has to be: acb ́d aédćb ́fg has not? Why not [[ X6. For all types besides NSM, BN, RLE, LRE, RLO, LRO, and PDF: a. Set the level of the current character to the current embedding level. b. Whenever the directional override status is not neutral, reset the current character type according to the directional override status. X9bis. Search backward from each instance of a NSM until the first character of other type is found. Change the type of the NSM to the type of the found character and set its level to the level of the found character. W1. (delete) ]]? In other words, make bidi absolutely transparent for NSM just like it is for ZWJ/NJ.
