[cairo] cairo_matrix_transform_point, only X or Y
spitzak at d2.com
Tue Aug 8 17:25:15 PDT 2006
If Cairo is doing rotations, the output x depends on both the x and y.
I have found it very useful to have a transformed_x(x,y) call that
actually returns the value. This makes it much easier to write code
because you don't need to define temporary variables to pass as
references, ie "foo(transformed_x(x,y),transformed_y(x,y))" rather than
"double tx,ty; transform(x,y,&tx,&ty); foo(tx,ty)". However Cairo
functions always returns an error status (right?) so such an api would
not fit in.
Gustavo J. A. M. Carneiro wrote:
> I found myself in a postion where I'd like to convert some code to
> transform coordinate systems over to use the cairo matrices APIs. I
> would like to use cairo_matrix_transform_point; however, in many places
> I only need to convert either X or Y, not both, and it seems wasteful to
> transform a dummy coordinate to throw it away.
> My question requires some knowledge of CPU performance in this case
> and I seek advice:
> 1- Should I prepare a patch to add cairo_matrix_transform_x and
> 2- Or is it pointless to optimise here?
> Any thoughts?
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