[cairo] Cairo Fill Rule - Alternate

Simon Budig simon at budig.de
Thu Oct 25 01:21:39 PDT 2012


Adhir Garg (adhir.garg at gmail.com) wrote:
> 
> I looked at MSDN GDI functionality at
> http://msdn.microsoft.com/en-us/library/windows/desktop/dd145080(v=vs.85).aspx
> It lists out ALTERNATE
> Selects alternate mode (fills the area between odd-numbered and
> even-numbered polygon sides on each scan line).

You misunderstood the description.

ALTERNATE "fills the area between odd-numbered and even-numbered polygon
sides on each scan line."

Note the crucial word "scan line". That is a row of pixels. Within this
rows the pixels switch between "filling" and "not filling" depending on
the number of polygon sides crossed (even or odd).

That is the same as CAIRO_FILL_RULE_EVEN_ODD.

That the description explicitely mentions "five sided polygons" is
misleading.

Bye,
        Simon

-- 
              simon at budig.de              http://simon.budig.de/


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