Dan Ingalls wrote:
 
> Here's one approach...
>    | f |
>    f _ (ColorForm mappingWhiteToTransparentFrom: (Form dotOfSize: 50))
>              colors: (Array with: Color transparent with: Color blue).
>    f displayOn: Display at: 200 at 200 rule: Form paint
> 
> This should display properly in every color depth, but you need the "paint" combination rule which treats transparency correctly.
> 
>         - Dan

This works with the exception of the offset value which gets set in
dotOfSize: ( a class method of Form).

The class methods for instance creation of Forms seems to be incomplete
or maybe immature. I don't know the history of the methods or how
they evolved, but I found the comment in the instance selector, center
(the subject of this post) intriguing.

My proposal is to embrace offset in Form and its decendants. I think
that there should be a private instance method like setExtent:depth:
which also sets the instance variables offset and bits to appropriate
initial values (offset _ 0 at 0. bits _ ????).


This new method would then cascade down to the various other instance 
creation methods. There are currently only four users of setExtent:depth:.
They are all in Form or ColorForm.

I am willing to make the changes if they are the right thing to do.
Otherwise I will go back to contemplating Squeaks navel.

Thanks,

John-Reed Maffeo