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## Re: [Gnash-dev] Matrix hell

 From: strk Subject: Re: [Gnash-dev] Matrix hell Date: Tue, 30 Sep 2008 10:49:26 +0200

```On Tue, Sep 30, 2008 at 10:31:31AM +0200, strk wrote:
> Zou, I'm having an hard time with that gnash matrix...
>
> This is the test:
>
> 1) Matrix is read from SWF:
>       (a=1, b=0, c=0, d=-2, tx=200, ty=200)
>       _xscale==100;
>       _yscale==200; // expected to be positive on extraction
>       _rotation==0;
>
> 2) _yscale is set to 100:
>       (a=1, b=0, c=0, d=-1, tx=200, ty=200) // 'd' expected to retain sign
>       _xscale==100;
>       _yscale==100; // expected to be positive
>       _rotation==0;
>
> 3) _yscale is set to -100
>       (a=1, b=0, c=0, d=1, tx=200, ty=200) // 'd' expected to change sign
>       _xscale==100;
>       _yscale==-100; // as set by AS
>       _rotation==0;
>
> 4) _yscale is set to 100 [ HERE GNASH FAILS ]
>       (a=1, b=0, c=0, d=-1, tx=200, ty=200) // gnash gives 'd=1'
>       _xscale==100;
>       _yscale==100;
>       _rotation==0;

Just an observation: from step (3) to step (4)
we're basically callin matrix::set_y_scale(100)
to a matrix that's already an identity.
There's no way we can have matrix::set_y_scale()
determine whether or not that 'd' element of the
matrix should be sign-swapped or not by only
taking _yscale ! The same input would result
in another output if the matrix was read as
an identity one from the start...

-strk;

```