Re: overprint bug (mkiv)

[Peter Rolf <indiego@gmx.net>]

Hans Hagen schrieb:
> Peter Rolf wrote:
>
>> overprinting is broken under very special conditions. You need to add 
>> framed content with a defined mp overlay as background and 
>> *deactivated frame* to a layer (last of the four pairs in the 
>> example). The text of the last pair is written in the same 
>> \GSoverprint group (in this case the \GSknockout is even missing). 
>> Very obscure.
>
>
> \def\reuseMPbox#1#2#3#4#5% space delimiting would save some tokens
>   {\xdef\MPllx{#2}%        but it's not worth the effort and looks
>    \xdef\MPlly{#3}%        ugly as well
>    \xdef\MPurx{#4}%
>    \xdef\MPury{#5}%
>    \forcecolorhack\getobject{MP}{#1}} % else no proper color intent
>
> the issue is as follows:
>
> - i use attributes for such things
> - and, in the backend i only look at glyph and rule nodes
> - however, the reused graphic is an object
> - so, i have a \forcecolorhack
> - this tells the backend to treat the following node as well
>
Thank you Hans (also for the nice explanation)! The minimal example 
works here, also the first test graphic. Nevertheless there is still a 
bug in the definition of \forcecolorhack. The error message of my second 
test graphic is the same as in

http://archive.contextgarden.net/message/20090901.094156.1dc47c81.en.html

So you should be able to produce the error with that example. The last 
time I simply used the old (commented) definition and everything worked 
again. I even looked at the definition of leaders that time (last used 
in LaTeX around eight years ago) and I think \zeropoint is no valid glue 
value here.

> there are a few more places where this is needed and in due time it 
> will be sorted out
>
I don't know if I should laugh or cry here. It took me nearly two days 
to make that minimal example. I'll interpret your last sentence as black 
humour... :)

Best wishes,  Peter

> Hans
>
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