[Therion] How to avoid that symbol-colour area blocks fills the blocks with chosen color

[Martin Budaj]

On Mon, Nov 5, 2012 at 8:33 PM, Bruce <bruce at tomo.co.nz> wrote:
> Martin, that may be the tip I have been looking for.  I will experiment with
> this sometime.  It also depends on how various pdf readers and printer
> drivers interpret the different approaches.

Besides Adobe Reader I get the best results using poppler-based
viewers, like Evince (especially regarding the rendering of
transparency groups).

> I presume your recommendation applies to areas defined using
> drawing/clipping to the path, and not areas defined using patterns?

Exactly.

The drawoptions were applied twice by MetaPost:
 * first time when drawing a symbol (e.g. block) to a temporary
picture -- this time the "thclean qq" command overrides the default
fill color (set by drawoptions) and fills the block area with a
(transparent) color of scrap background
 * second time when this picture was (after clipping) added to other
symbol drawings -- in this case MetaPost applies the default color to
all lines (block border) and areas (interior of a block) drawn in the
temporary picture.

> And is it better to use
>  drawoptions();
> or
>  thdrawoptions();
> ?

They are used independently, but if you set the same option (like
color) using both of them, drawoptions has a higher priority.
Currently therion uses drawoptions to specify symbol colors and
thdrawoptions are used in symbol definitions to specify dashed lines.

Martin