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Re: modify coord-rotate to get exact values for (sin PI) etc (issue 2695

From: David Kastrup
Subject: Re: modify coord-rotate to get exact values for (sin PI) etc (issue 269530043 by address@hidden)
Date: Fri, 30 Oct 2015 21:03:18 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux)

Werner LEMBERG <address@hidden> writes:

>> I'd argue for creating functions sind, cosd, angle in analogy to
>> METAFONT's functions.  And we'd use them exclusively so it might
>> make some sense to define C++ versions of them and export them in
>> order to get consistent results.
> Maybe there's a library out there which we could use, probably even
> GNU stuff?

I'd be surprised as that is rather basic stuff.  Wait.

    pango_matrix_rotate ()

    pango_matrix_rotate (PangoMatrix *matrix,
                         double degrees);

    Changes the transformation represented by matrix to be the
    transformation given by first rotating by degrees degrees
    counter-clockwise then applying the original transformation.

We are linking Pango anyway.  Maybe we should convert all our stencil
stuff into native Pango?  The unwholesome mess we pass around for path
expressions and convert back and forth is not particularly efficient.

And being all-Pango would make it easier to create more backends.  Even
if Pango's own PDF backend is not good enough (for dealing with
metadata, tables of content and similar stuff), the intermediate
representations should still be a good common denominator.

David Kastrup

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