Layers

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Revision as of 15:03, 9 March 2007 by Maarten-Jan (talk | contribs) (made some corrections and added to Layers and Graphics categories)
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< Layout | Columns | Overlays | Logos >

Layers are ConTeXt's mechanism for absolute positioning of elements and other advanced techniques like switching elements on and off.

There's still no manual about them.

My first Layer

Define a layer that takes the whole page

\definelayer	[mybg]	% name of the layer
		[x=0mm, y=0mm,	% from upper left corner of paper
		width=\paperwidth, height=\paperheight] % let the layer cover the full paper

Now you can put something in that layer:

\setlayer	[mybg]	% name of the layer
		[hoffset=1cm, voffset=1cm]  % placement (from upper left corner of the layer)
		{\framed[frame=on, width=3cm, height=2cm]{LAYER}}  % the actual contents of the layer

Activate the layer as a background:

\setupbackgrounds[page][background=mybg]

This command makes the layer appear only once after the background is activated. If you want to repeat the layer on each page, use the option repeat=yes in the \definelayer command.

Placement

There are several possibilities for defining the placement of layer content:

  • x, y : offset from upper left corner of paper
  • hoffset, voffset : offset from upper left corner of layer
  • corner : reference point, something like {left, top}
  • location : alignment of the element relative to the corner, something like {right, bottom}
  • preset : a named location, see below

There are some "presets" for paper egde placement:

% These four are defined by ConTeXt!
\definelayerpreset	[lefttop]	[corner={left,top}, location={right,bottom}]
\definelayerpreset	[righttop]	[corner={right,top}, location={left,bottom}]
\definelayerpreset	[leftbottom]	[corner={left,bottom}, location={right,top}]
\definelayerpreset	[rightbottom]	[corner={right,bottom}, location={left,top}]

Similarly you can define your own presets.

Links


TODO: We need a lot of documentation and samples for this complicated subject. (See: To-Do List)