Re: Backend and non-backend (was Re: Stencil bounding box)

[Johannes Schindelin]

Hi,

On Tue, 2 May 2006, David Feuer wrote:

> On 5/2/06, Johannes Schindelin <address@hidden> wrote:
> 
> > 
> > This is worse than what Han-Wen suggested. His suggestion is easy, makes
> > sense and would improve development. Why come up with other ideas?
> 
> I don't understand what he means by bbox overlap areas.  Maybe that's
> my problem?

Then say so!

A bbox (short for "bounding box") of an object is a rectangle which is the 
minimal enclosing rectangle [1]. Typically this is written as x0 y0 x1 y1 
where x0 < x1 and y0 < y1.

Now, the overlap area between two bboxes is just the intersection, which 
is again a rectangle, or empty.

If you have two different versions of LilyPond, the same object could be 
subtly moved between the two. But if you measure the area of the overlap 
area between old and new bbox, you have a pretty good idea how much the 
result deviates from the original.

And if somebody wants to try a super-cool idea, that measure will not only 
tell how much the output has changed, but also where to look for the 
largest effect.

Hth,
Dscho

Footnote [1]: Strictly speaking, it is a Cartesian rectangle, i.e. its 
sides are parallel to the axes.