Input and compilation/PDF/PDF viewer layers
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PDF has a concept of layers that you can enable and disable (at least in a few viewers). The official name is “optional content groups” (OCG). This has nothing to do with ConTeXt’s Layers.
There’s no other documentation yet, maybe have a look into the sources attr-lay.mkiv, attr-lay.lua and lpdf-ren.lua. It’s also used in some presentation styles.
\defineviewerlayer[Plane] \setupviewerlayer[Plane][ state=start, visible=no, % initially title=Test, %tag=, % don’t know? editable=yes, % in Acrobat Pro? printable=yes, export=yes, % exportable in xml? scope=global, % or local ] \starttext \input tufte \startviewerlayer[Plane] {\bfa TOP SECRET} This information is on a different plane of existence. \stopviewerlayer \input knuth \viewerlayer[Plane]{Some more hidden text...} \stoptext
You can switch the visibility of layers with the JavaScript functions HideLayer and VideLayer (from scrn-fld.mkvi:
\defineviewerlayer[test] \startviewerlayer[test]Hide Me\stopviewerlayer \defineoverlay [WithTest] [{\overlayrollbutton[HideLayer{test}][VideLayer{test}]}] \framed[background=WithTest]{toggle}
Viewer layers are known to work within \setlayer (see Layers), e.g. meta-ini.mkiv.