[openbeos] Re: ShowImage "Mirror" Operations

"Ryan Leavengood" <leavengood@xxxxxxxxx> wrote:
> On 4/22/06, Joachim Seemer <j.seemer@xxxxxx> wrote:
> >
> > There's no reasons to ever block when doing something 
> > that has even the remote possibility to take noticable time.
> 
> In general I would agree, especially on a system like BeOS/Haiku 
> which
> is so pervasively multi-threaded. But in this particular case I'm not
> sure how much it gives you. As I said in the last email, if the
> operation is something that changes the image so much (such as
> flipping or rotating), the program could not allow you to change it
> anyhow while it was being flipped or rotated. The only thing
> applicable in my opinion is maybe a preview or a progress bar and a
> cancel button, but really those are overkill for a small app like
> ShowImage.

If ShowImage is to process a time-consuming lossless rotation 
at _opening_ an image for display, it might be courteous to 
display the unrotated image and a progress bar / activity hinter, 
instead of nothing, for a couple of seconds.

It should be possible to move to the next or previous image, 
or to quit ShowImage entirely, without having to wait for the 
processed _display_ of the image to finish. 

If the user has just opted to rotate or flip an image, and the 
action is indeed the lossless* variant that merely writes an
attribute (on BFS), the user should be free to move on with 
some other task, as soon as the attribute has been written,
not being held back by the new display of the image that is
being computed.

* What is lossless
Outside of BeOS is often means that the very same data is
written back, re-ordered, or some native feature of the format
is used to do changes neutral to core data. 

I honestly don't know if the jpegs can be 100% losslessly
rotated and written to disk. It's not a lossless format to begin with.

Most people don't care, I suppose, but it could start showing
in the images, if an application lets you do lossy actions on them
and you play with the same image one too many times.

/Jonas Sundström.

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