I only tested this with Calc and xls files. 1. Open a file in read-write mode (the default). 2. Next, choose File > Open from menu. 3. Check the "read-only" box in the open file dialog. 4. Select the same file that is already open read-write. 5. Click "Open." Result: Nothing. In particular, there is no indication that the file has changed state to read-only. I say this based on no such indicator in the window title, and no graying-out of editing buttons. (I have not checked the actual status of the file handle.) Expected result: Mode of that file should toggle from read-write to read-only, probably with a warning that changes might be lost. That is what the very old version of Excel that I use does. Operating System: Windows 7 Version: 4.2.5.2 release
Confirmed with LO 3.6.7.2, 4.2.5.2, 4.3.0.1 - Ubuntu 12.04 x86 Rare case, we can close the file first before reopening same file in read-only mode, but it's a misfunction
I tested writer and calc. In both cases, if the file was already open, then trying to open it again in read-only mode did nothing - the file remained in read-write mode.