1. Create a new document in Calc.
2. Put the text "abc" (no quotes) into cell A1 and the number 123 into cell B1.
3. Drag over the 2 cells so they are both selected. An autofill handle appears on cell B1.
4. Drag the autofill handle down a row. Don't release it yet.
5. Notice that the tooltip says "abc". Now you can release the mouse button.
6. If the autofill is done on just column B instead of both columns A & B, the tooltip says 124, 125, etc. as the mouse is moved to successive rows.
The desired behaviour is that the tooltip would say 124, 125, etc. (based on the first numeric cell found in the starting range of the autofill) even when both cells A1 & B1 (in this case) form the starting range of the autofill.
A user can forget the linear-progression default behaviour (i.e., without the Ctrl key) of autofill and try to autofill "abc 123" expecting to get "abc 123" on all successive rows of the autofill. The current tooltip does not notify the user that the result will actually be "abc 124" etc.. The requested change would have the tooltip notify the user of this, so preventing the unexpected results which would require an Undo.
LibreOffice 18.104.22.168 on Ubuntu 13.04.
and what if you have the text in B1 and numbers in A1?, or if both are numbers?
With text in B1 & numbers in A1, the current behaviour is that the tooltip shows an incrementing number (for column A) as the autofill handle is dragged to successive rows (2, 3, etc.). This is fine because it indicates, while the mouse button is down, what will happen once the mouse button is released.
With numbers in both cells, currently the tooltip is based on cell A1. Again, this indicates that autofill will place incrementing numbers rather than just duplicating the contents of the selected cells. I have no reason to ask for this to be changed at this time.
Then better change the status from normal to enhancement