Format plug-in: Setting file properties/metadata

Question

Hello,
I am currently writing a plug-in to import a proprietary image format into Photoshop. The people who will use this plug-in believe it would be useful to have some file information displayed in the File Info dialog.
The problem I'm running into is finding the functions necessary to set these properties in the File Info dialog, as currently they are all entirely blank.
As a simple example, if I wanted to have the Document Title, Author, Description and Keywords read "Hello, world!" after I've read in an image, what functions would my plug-in have to call to set each of these text fields?
Is there a struct that my plug-in needs to modify, or a group of get/set functions to change these properties?
Any information would be extremely helpful, as documentation on the subject is very difficult to find in the SDK.
Thanks a lot!
Jack

Answer 1

Thanks for your help, Toby.
I've got an idea of how to configure the properties at this point. Simple properties work now, but I am still running into a bit of trouble setting complex options such as the Caption tag. I create a handle, populate it with the null-terminated string for the caption, and then I use setPropertyProc to link that handle to propCaption. The code would go something like this:
>Handle h = sPSHandle->New( captionLength );
>if( h )
>{
> Boolean locked;
> Ptr p;
>
> sPSHandle->SetLock( h, true, &p, &locked );
> // In here, use memcpy to copy a typical C string into p
> sPSHandle->SetLock( h, false, &p, &locked );
>
>sPSProperty->setPropertyProc(kPhotoshopSignature,propCaption,0,0,h);
>}
Basically when I run my plugin and open a file, the Description field is still blank, as it was before I tried to populate the fields.
Is there something wrong with my approach? Incidentally, I also encounter the same problem when I use the same property and handle suite methods that you do (FormatRecord->PropertyProcs and FormatRecord->HandleProcs instead of sPSProperty and sPSHandle respectively). From looking at other available code online, I'm assuming that there isn't a difference in behaviour. Please correct me if I'm wrong! :)