The inverse of the transformation matrix that transforms user space to
surface space (i.e. device space) can transform coordinate input to the
coordinate system the user (programmer) is working in.

Depending on the scale of the transformation it's possible for the result
to be inaccurate to a degree that the result is inaccurate, but that can
easily be cured with a function that returns the input coordinates in
surface space, which uses should use if the scaling factor of their
transformation from user space to surface space is large enough.

-Mike



On Wed, Jun 19, 2019, 22:38 Rene Rivera via SG13 <sg13_at_[hidden]>
wrote:

> On Mon, Jun 17, 2019 at 7:31 PM Tony V E <tvaneerd_at_[hidden]> wrote:
>
>> I can only imagine that mouse/touch input needs to be in the same
>> coordinate system as the drawing.
>>
>
> It almost never is at the device level. Although the higher level APIs
> users are accustomed to do commonly transform to "drawing" coordinates.
>
> --
> -- Rene Rivera
> -- Grafik - Don't Assume Anything
> -- Robot Dreams - http://robot-dreams.net
>
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