polylist toys

[panagiotis m]

Hello,

Thank you all for the useful comments.

I *think* the LCB feature in LC 10 Steven mentioned is the "is
valid" operator, that returns a boolean value indicating whether or not the
image data is valid.
Also, note that in the upcoming releases of LC 10 we will add syntax for
checking if a file/directory exists, so we could check not only image
validity but also image existence in the first place.

BTW, we have found a workaround for allowing this stack (lazy image
example) to work in LC 9 as well. The updated bundle will probably appear
in your account area in the next couple of days.

Kind regards,
Panos
--

On Fri, 19 Aug 2022 at 01:13, Alex Tweedly via use-livecode <
use-livecode at lists.runrev.com> wrote:

>
> On 18/08/2022 17:34, Steven Crighton via use-livecode wrote:
> > Hi Mike,
> >
> > I just tested the lazy load example and hit populate and clicked around
> etc and could not trigger an error.
>
> As already confirmed, that problem is fixed in 10.
>
> However, the lazy load example still contains bugs due to race
> conditions, some of which I described in some forum post somewhere (Boy
> do I hate the forums! Surely there's some way to check what posts I have
> done myself).
>
> Thinking about it more, there are other race conditions which are
> perhaps more obscure, but more serious. I know it's only an example, and
> maybe can't be expected to be bulletproof, but as an example of how to
> do Lazy Loading it is (IMHO) really too naive and simplistic. People
> expect to take those examples and just use them.
>
> The obvious race conditions are:
>
> 1. if multiple entries reference the same image, then there is a chance
> the earlier ones never get properly updated (sURLToIndex[pURL] will have
> been overwritten by the next call to onlineImage before the image value
> gets set).
>
> 2. if the user (or anything else) resets the dataContent of the widget
> while there are outstanding "load URL"s, then when the downloadComplete
> is triggered, it will set the image value for some random new item to
> the image of the earlier one.
>
> 3. And if the one which was wrongly set in case 2 above also happens to
> be a URL that occurs multiple time (i.e. case 1 above), then that
> wrongly set image will remain "forever".
>
> Alex.
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