I have brought this to the attention of the gThumb developers and they
suggested bringing this request to this list since the standard detect
algorithm is:
if (file.mtime != thumb.MTime) {
recreate_thumbnail ();
}
The 1-second granularity of mtime causes trouble when a file is being created slowly in chunks - for instance, when a RS232-connected scanner or a device like an oscilloscope is saving images to disk.
For example, gnome may try to thumbnail the incomplete file at t=10.1 seconds, and create a "failed" thumbnail associated with that filename+mtime. The device may then save the final bit of the file at t=10.4 seconds, but apps will still use the failed thumbnail.
gThumb ignores failed thumbnails (and attempts to re-thumbnail) if the mtime is within the last 5 seconds to avoid this problem (because I really do use gthumb with my oscilloscope...)
Anyway... some of these odd problems could be avoided if the original-file-size was also saved (as a png text chunk) along with the mtime, and both the mtime and the file size were checked. (This would be backward compatible - new apps would use the original-file-size check if the thumbnail had the original-file-size encoded.)
Is there any hope of changing the thumbnailing spec? - Mike