Re: [boost] GUI coordinate units (Was: GUI foundations)

From: Vladimir Prus (ghost_at_[hidden])
Date: 2005-10-05 01:45:49

Andy Little wrote:

> 
> "Vladimir Prus" <ghost_at_[hidden]> wrote
>> Andy Little wrote:
> 
>>> Just provide alternative unit systems. Then we can all choose the ones
>>> we want, when we want.
>>>
>>> Hows that?   :-)
>>
>>    template<class CoordinateUnit>
>>    class Widget {};
>>
>> ?
>> Well, over my dead body ;-)
> 
> 
> The cleanest way to deal with units would be as a world to device
> transform which is applied to the window at runtime as has been mentioned
> before. So it would be:
> 
> Transform  t;
> Widget  w(t);
> 
>  ... code dealing with coordinates needs only use floats or ints ,
> 
> Now you can change the transform to whatever unit you wish. and your code
> will
> be units independent.  Of course the default could be pixels so that "old
> timers" such as yourself who may be slightly frightened of units dont ever
> have to see them. ;-)

Good. In fact, that's why I meant by "2D graphics can be scaled as you
like". Specifically, take a look at:
   
   QPainter::setWindow
   http://doc.trolltech.com/4.0/qpainter.html#setWindow-2

that establish logical coordinates for drawing, and

   QPainter::setMatrix
   http://doc.trolltech.com/4.0/qpainter.html#setMatrix

that establish translate/scale transformations.

Is that what you're after?

- Volodya