Re: [pygame] MacOS/PyGame/PyOpenGL mouse inversion

["Dave LeCompte (really)" <dave@xxxxxxxxxxxx>]

This is all good knowledge to have, to be sure, but I think we're
wandering afield from my original issue - I didn't want to ask about the
default OpenGL coordinate systems, I'm reporting that the same code
behaves differently on a Mac in a window than anywhere else.

Run the code fullscreen on a Mac, it behaves as I expect. Run the code on
a  MSWindows PC, it behaves as I expect.


I'm proceeding with the understanding that this is a known and resolved
bug in the Mac SDL code and will be fixed when the 1.8 (final) binaries of
PyGame are ready.


Thanks,
Dave LeCompte

> On 1/17/07, Chris Ashurst <CAshurst@xxxxxxxx> wrote:
>> I think on all systems (and if you're used to getting mouse x/y
>> coordinates
>> via the SDL side of pygame) the mouse is "flipped" when you use OpenGL.
>>
>> People with more experience with OpenGL can probably clarify, but I have
>> hit
>> this same issue before, too. I think the x coord turned out to be fine,
>> all
>> I needed to do was write a function that inverted the y coordinate to
>> get
>> the "real" value.
>>
> If your use of openGL changes anything about the mouse coordinates
> returned from pygame, then I think it's a bug, like Alex says. Moving
> the mouse down (towards you) should always make it's y position
> increase, and moving it up (away from you) should always make it's y
> position decrease.
>
> However, when it comes to window coordinates, openGL by default uses a
> coordinate system where 0,0 is the lower left, and positive x goes
> right and positive y goes up. This is different from most computer
> systems where y goes down and 0,0 is the upper left. OpenGL uses the
> system it does because it follows the conventions of the cartesian
> coordinate space used in math & physics. The place where you'd notice
> this the most in games is when using trig functions like sin & cos,
> which also are designed for math & physics & openGL coordinate systems
> (positive rotations are counter-clockwise, 0 degrees is straight right
> & y is up)
>
> So basically, I'm saying it's not that the mouse is "flipped" with
> OpenGL, it's that unless you set up your transforms to change it,
> OpenGL is "flipped" from what all the pygame/SDL and desktop position
> stuff is
>