@CyrilleB79, could you please have a test?

Tested from source (commit eeb7e49) with one property having default value (underline) and one property having no specific default value (font size). I confirm that the reported issue is fixed, i.e. moving from cell to cell reports the property only when it changes.

However I can see a non critical change of behaviour with the following STR:

• Type "The cell's content" in a cell
• Format it to underline
• Press Alt; the ribbon is focused
• Press alt again; the cell is focused again.

At last step, with NVDA 2023.1, we can hear: "Sheet2 table 11.0 pt underline The cell's content".

With this PR instead, we can hear: "Sheet2 table The cell's content", i.e. formatting is not reported again.

@CyrilleB79 Thanks for testing. I think that finding, though it is a change, is consistent with how this happens in Word. For example:

1. Enable font attribute reporting
2. Open Word
3. Type "hello"
4. Select + underline
5. Open and close the ribbon.
6. Observe that NVDA will only report Underline after pressing down arrow, for example. It doesn't on first occasion.

@CyrilleB79 Thanks for testing. I think that finding, though it is a change, is consistent with how this happens in Word. For example:

1. Enable font attribute reporting
2. Open Word
3. Type "hello"
4. Select + underline
5. Open and close the ribbon.
6. Observe that NVDA will only report Underline after pressing down arrow, for example. It doesn't on first occasion.

No, I disagree.

With your STR, in Word, it does not report immediately when leaving the ribbon. But if you ensure that the word "Hello" is not selected, e.g. just put the caret between the two l's of "Hello", you will have "underline" reported as soon as you leave the ribbon.
The same way, in Excel with NVDA 2023.1, if you have only one cell selected, the attributes are reported as soon as you leave the ribbon. But if you have a multi-cell selection, the attributes are not reported until you turn back to a single cell selection.
This has probably to do with the fact that NVDA does not report formatting when dealing with selection.

* Type "The cell's content" in a cell

* Format it to underline

* Press Alt; the ribbon is focused

* Press alt again; the cell is focused again.

At last step, with NVDA 2023.1, we can hear: "Sheet2 table 11.0 pt underline The cell's content".

With this PR instead, we can hear: "Sheet2 table The cell's content", i.e. formatting is not reported again.

I actually can't reproduce this. For me the behavior is that underline is reported properly.

1. Focus a1
2. Type hello
3. press enter, focus is at a2
4. move up to A1
5. Press ctrl + u to underline
6. press alt twice

NVDA ssays: sheet 1 table underlined hello A1.

Sorry, my STR was not complete enough.

If you take your STR, add the following steps to reproduce the issue:
7. Press again alt two times

Or alternatively:
Step 5.5 (between 5. and 6.): press rightArrow, then leftArrow

Never mind, the approach I used was way to complex. I changed this pr with a two lines fix that should work as expected.

Never mind, the approach I used was way to complex. I changed this pr with a two lines fix that should work as expected.
I have tested it and all goes well. Nice fix!

Setting oldSelection.parent to self when oldSelection.parent == self is not very intuitive when reading the code. Maybe you could add a comment to explain this lines of code? It also appears later in the function with oldSelection.parent==newSelection.parent.