LibreOffice Writer: Line numbers announced when navigating but not editing.

[Qchristensen]

In LibreOffice 5.4.2.2 and NVDA 2017.3 (also Next 14541) when Line numbers are enabled in NVDA's document formatting, they are only read aloud when navigating (eg using up and down arrows), not when typing (eg pressing enter to move to a new line).

In Braille, each line is denoted with the number symbol and line number before the text on each line when navigating, as expected. When ENTER is pressed to move to a new line. The line number itself (with no number symbol) is displayed at the start of the line. When something is typed on that line, the number symbol and line number are displayed at the start of the line.

To reproduce:

1. Ensure Line numbers are checked in NVDA's document formatting dialog.
2. Create a blank document in LibreOffice writer. If using a Braille display note that dot 1 is shown in the leftmost cell, with the flashing dots indicating this as the current cell. (In Word, there would be the number symbol, then 1, then a blank cell, then the active cell).
3. Type "a". The braille display now shows the number symbol, 1, space, then a. Only the letter typed is read aloud.
4. Press ENTER to move to a new line. The Braille shows the number 2 (letter b) with no number symbol in the first cell, which is the active cell.
5. Press up arrow. NVDA reads "a". It does not read the line number aloud. The Braille display shows the number symbol, 1, space, then a.
6. Press down arrow. NVDA reads "Line 2 blank" aloud, and indicates this correctly on the Braille display.
7. Press up arrow. NVDA reads "Line 1, a". and again indicates this correctly on the Braille display.

In Step 5 above, it seems if you press enter to move to a new line, then immediately navigate to another line without typing anything, it doesn't read the line number you move to. If we had typed a letter in between steps 4 and 5, it would have read Line 1 correctly.

Issue on LibreOffice bug tracker 78963: https://bugs.documentfoundation.org/show_bug.cgi?id=78963