[racket-dev] Caching rendered icons

I think this is a great example to base a tutorial example on. Neil:
I'd be happy to help with the writeup, if you'd be willing to make a
first attempt.

Robby

On Thu, Jan 12, 2012 at 3:01 PM, Neil Toronto <neil.toronto at gmail.com> wrote:
> On 01/12/2012 11:52 AM, Matthew Flatt wrote:
>>
>> At Thu, 12 Jan 2012 11:19:55 -0700, Neil Toronto wrote:
>>>
>>> 2. Compile time: Provide macros that render icons during expansion and
>>> try to store them in the "compiled" directory.
>>
>>
>> Do you need icons to be in separate files? A macro could expand to a
>> byte-string literal, since it's just as easy to generate a bitmap from
>> a PNG byte string as from a PNG file.
>
>
> This is friggin' awesome. The expression
>
>    (compiled-left-arrow-icon '(255 95 78) 24)
>
> expands to
>
>    (make-object bitmap% (open-input-bytes bs) 'png)
>
> where `bs' is a literal byte string produced at compile time by
>
>    (define bm (left-arrow-icon color-val height-val))
>    (define p (open-output-bytes))
>    (send bm save-file p 'png)
>    (define bs-stx (datum->syntax stx (get-output-bytes p)))
>
> The hardest part is parsing the color and height syntax, but `syntax/parse'
> makes it easy enough. There is no distribution problem, no versioning,
> hashing, caching, or unused bitmap cleanup. I can't think of a better
> solution, and I couldn't have done it in any other language.*
>
> Racket so rocks.
>
> Neil T
>
> * Okay, I could have done it in some Lisp, but not safely or easily.
>
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