Making sense of choices at Metadata > Edit XMP(IPTC) > Options. Or maybe a bug?

[KLE-France]

I'm not sure if the following is a bug or me not understanding something, so I'll start here in General Support.

When modifying XMP or IPTC data on multiple images at once, the "Options" tab has three choices:

Keep and add new value (Keywords [and supplemental categories])

Keep original value if new value is empty

Replace only if original value is empty

The following concerns only the last two.

Here's what's happening to me:

Select multiple images that have star ratings in them > Metadata > Edit XMP > ("Don't load field values" is checked) > Options tab:

"Keep and add new value (Keywords)" is checked

"Keep original value if new value is empty" is checked

"Replace only if original value is empty" is unchecked (because I want to change an existing value)

> Description tab > put new value in "Author" > Click "Write to all files"

⇒ This erases my star ratings.

When "Replace only if original value is empty" is checked, the star ratings do not change.

But this doesn't make sense to me. I am NOT putting a new value into the star rating, so this latter should be considered to have an "empty" new value. Thus, it seems to me, that a checked "Keep original value if new value is empty" should protect the star ratings...

But that's not what happens.

In this case at least, XnView seems to consider the default rating of no stars NOT as an "empty" value but as a rating of zero stars. This would explain why having an unchecked "Replace only if original value is empty" lets XnView change the star rating, but having it checked doesn't.

Donc, am I simply daft? Is this a bug? Or is this just something we need to live with?

Thanks in advance to all!

[xnview]

do you have the problem only with rating?