On 17/04/15 19:59, H. S. Teoh via Digitalmars-d wrote:
There's also the question of what to do with bidi markings: how do you handle counting the columns in that case?
Which BiDi marking are you referring to? LRM/RLM and friends? If so, don't worry: the interface, as described, is incapable of properly handling BiDi anyways.
The proper way to handle BiDi line wrapping is this. First you assign a BiDi level to each character (at which point the markings are, effectively, removed from the input, so there goes your problem). Then you calculate the glyph's width until the line limit is reached, and then you reorder each line according to the BiDi levels you calculated earlier.
As can be easily seen, this requires transitioning BiDi information that is per-paragraph across the line break logic, pretty much mandating multiple passes on the input. Since the requested interface does not allow that, proper BiDi line breaking is impossible with that interface.
I'll mention that not everyone take that as a serious problem. Window's text control, for example, calculates line breaks on the text, and then runs the BiDi algorithm on each line individually. Few people notice this. Then again, people have already grown used to BiDi text being scrambled.
Shachar
