On 07/29/2016 12:26 PM, George Neuner wrote:
> I don't see any obvious utility in being allowed to create a zero
> sized bitmap. Likewise a widget or a canvas.
It is useful when writing code that handles images generically. For
example, and this is a real example where the zero-size-bitmap error bit
me the other day, when rendering `2htdp/image`s to `bitmap%`s.
Here's the code I have now:
(define w (max 1 (image:image-width i)))
(define h (max 1 (image:image-height i)))
where previously it was
(define w (image:image-width i))
(define h (image:image-height i))
I consider the `(max 1 ...)` to have made my code less elegant and more
brittle.
*Negative* dimensions don't make sense. But zero dimensions do. (I feel
like I want to waffle about closure properties...)
> IMO a zero dimension should be an error. If you don't know how big
> the bitmap should be, don't create it until you do.
In the case I was facing, rendering `2htdp/image`'s `empty-image` to a
`bitmap%`, I knew exactly how big it should be: 0x0. I think supporting
0x0 bitmaps makes good sense and helps avoid brittleness and inelegance.
Tony
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