Re: subsurfaces origin attribute Re: [pygame] PixelArray question

[Phil Hassey <philhassey@xxxxxxxxx>]

Hi,

I would like this feature too.  It'd be quite useful for gui dev... Here's an example:

- Say your screen is 640x480.
- Say you're drawing Dialog, but it's half dragged off screen (for some reason), so it's Rect would be: Rect(600,400,400,300) - putting it mostly outside of the screen.
- Doing screen.subsurface(r) will raise an error

What would be convenient is if .subsurface() would do this:

- It didn't raise an error
- It would return a subsurface
 - get_width, get_height would return 400,300
- The surface would have it's clip set to (0,0,400,300)
- If you wanted to, you could change the clip to (-40,40,480,380) and be able to draw *outside* of your subsurfaces region with blits to (-40,40) etc.

Not sure if I explained all that quite right, but it would be a pretty useful feature :)

The implementation I just described would not be entirely backwards compatible with pygame, as the clipping region would be
 used for something special in this case.  So you might have to call it something like subarea() or some such method.

(This can all be emulated in python, but having a proxy-surface makes everything a bit slower, though I'm not sure how much ...)

Phil
 
René Dudfield <renesd@xxxxxxxxx> wrote:

Hi,

I'm not sure I understand how that would work? Could you please
explain it with code?

I think it sounds useful though - just not sure I understand.


On 8/24/07, Greg Ewing wrote:
> Lenard Lindstrom wrote:
> > As for slicing, that is just a generalized form of Surface.subsurface
> > (with the parent locked for consistency with surfarray).
>
> Speaking of subsurfaces, there is one thing that I wish
> they had, and that's the ability for the origin of the
> subsurface's coordinate system to be somewhere other than
> its top left corner.
>
> This would have been useful in a small GUI library I wrote
> recently, where to draw a subwidget I get a subsurface from
> the parent widget's surface and pass it to the subwidget's
> draw() method. But this means that a subwidget can't hang
> outside the bounds of its parent widget, as that causes
> subsurface() to throw a wobbly.
>
> If surfaces had an "origin" attribute, subsurface() could
> simply clip the subsurface and set its origin appropriately.
>
> --
> Greg Ewing, Computer Science Dept, +--------------------------------------+
> University of Canterbury, | Carpe post meridiem! |
> Christchurch, New Zealand | (I'm not a morning person.) |
> greg.ewing@xxxxxxxxxxxxxxxx +--------------------------------------+
>

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