[NTG-context] Disable reuse of figures
Hans Hagen
j.hagen at xs4all.nl
Sat Feb 19 11:26:56 CET 2022
On 2/19/2022 7:30 AM, Aditya Mahajan via ntg-context wrote:
> Hi,
>
> This is related to a bug report for the filter module:
> https://github.com/adityam/filter/issues/60
>
> Normally, when the same figure is included twice, context only includes the figure once and refers to the included figure the second time. The option `object=no` to externalfigure is supposed to prevent that, but it doesn't work. For example, consider the following example the bug-report uses graphviz as the external program, but I have changed that to context to keep things self contained)
>
> \usemodule[filter]
>
> \defineexternalfilter
> [graphviz]
> [
> filter=context --purge,
> output=\externalfilterbasefile.pdf,
> readcommand=\ReadPDF,
> ]
>
> \def\ReadPDF#1%
> {\externalfigure[#1][object=no]}
>
> \starttext
>
> Circle:
> \startgraphviz
> \startMPpage
> draw fullcircle scaled 1cm;
> \stopMPpage
> \stopgraphviz
>
> Square:
> \startgraphviz
> \startMPpage
> draw fullsquare scaled 1cm;
> \stopMPpage
> \stopgraphviz
>
> \stoptext
>
> Behind the scenes, the first \startgraphviz ... \stopgraphviz environment writes the content to an external file (\jobname-temp-graphviz.tmp), runs `context --purge \jobname-temp-graphviz.tmp`, which creates `\jobname-temp-graphviz.pdf`. The `\ReadPDF` macro then includees the file (with object=no).
>
> At the next \startgraphviz .. \stopgraphviz, the same process is repeated. The `\jobname-temp-graphviz.pdf` file is overwritten and the new file should have been included. But it is not. The output contains the first image twice.
>
> I thought that object=no should have prevented the reuse. In fact, if I compile the file with luatex, I get an error message:
>
> ! error: (pdf inclusion): file has changed '12-two-outputs-temp-graphviz.pdf'
> mtx-context | fatal error: return code: 256
>
> Any idea why object=no is not working?
the pdf file is kept open, for various reasons:
- performance
- the might be different pages to fetch
- analysis happens when the image is placed, inclusion happens later
so you try to reopen an already open file (which has not been completely
processed)
Hans
-----------------------------------------------------------------
Hans Hagen | PRAGMA ADE
Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
-----------------------------------------------------------------
More information about the ntg-context
mailing list