[cells-devel] gui-geometry

[Kenny Tilton]

>>> If the former, when you have time, would you mind writing up a short
>>> guided tour of gui-geometry?  Even if it was just to explain what all
>>> the abbreviations like :lx, :ly etc meant.  Did you base it on some
>>> other framework and I could look up the docs for that?
>> I am pretty busy, so here goes (and i will start by saying my approach
>> translates (haha, pun unintended) nicely to OpenGLs view of coordinates, but
>> that doc wont help). No big deal, the idea could not be simpler:
>>
>> I will describe an OpenGL-like geometry in which up is positive and negative
>> is down, the opposite of most GUIs (so be careful!). I /do/ have some
>> support in gui-geometry for the idea that the signs for up and down may vary
>> -- look for macros like down and up that take care of using the right sign
>> given some global parameter I forget.
>>
>> Every geometer (widget) has its own coordinate system defined by a local
>> bounding rectangle, left top right and bottom. The word "local" gives us the
>> "l", the individual bounds give us another l for left then r, t, and b for
>> an end result of ll, lt, lr, and lb. We allow ll and lb to be specified
>> because sometimes it is useful to specify negative values. ie, the origin (0
>> 0) would not be at the bottom left corner. As an aside, i have never tried
>> making those positive such that the origin would lie outside the bounding
>> box, but that should be OK.
>>
>> In hierachies of geometers, their geometries nest. (px py) tell us where in
>> our parent our origin falls.
>>
>> That's it! 

The OpenGL tie in, by the way, is that all drawing is done relative to 
an abstract origin. In OpenGL I will create a chunk of code to draw the 
wheel of a car, standing on edge, hubcap to right, with the center of 
the axis running through the the hub as (0 0 0). My caller can then use 
glTranslate and glRotate to draw four wheels around a car, all hubcaps 
facing out, and even have then spinning.

Likewise, all my drawing in GUIs using gui-geometry is done relative to 
an origin.

kt