I have recently upgraded Libreoffice on both Linux Mint 19 and Ubuntu 16.04 to 6.3, but there were too many odd things happening like the cell highlighting tool is greyed out and the Text Formatting toolbar has disappeared - very annoying to have to call it up from the menu each time. So on Ubuntu I uninstalled Liboff 6.3 and installed 6.2.7 All ok except after resizing a window in an .ods the file then would not display on the screen even though it was open. Then it started happening to a .odt file. This makes Liboff unusable.
In trying again to open an .odt I found that the window had actually shrunk to a spot on the screen which I could carefully extend out by careful use of the mouse. I have no idea why it would have shrunk to almost nothing. This has happened on resizing windows for both odt and ods.
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Since I dragged the odt file window out to be bigger I have not been able to make it "disappear" again. At the time it happened on Ubuntu 16.04 I had an ods and an odt file open on the screen, both reduced in size a bit to be able to see both at the same time. After minimising the odt, from this point it "disappeared" on un-minimising it. It was only later I discovered that it had been reduced to a dot on the screen. The other odd thing which I didn't mention before is that I get two rows of menu headers at the top of the screen not just one: File Edit View etc when viewing either odt or ods. This by the way is having gone back to using Libreoffice 6.2.7.1 The reason I abandonned Libreoffice 6.3 was that the odd things as explained before that were happening on ods files on both Ubuntu 16.04 and on Mint 19.1 were making it inconvenient to use. Strangely when I checked on Windows 7 Libreoffice 6.3 actually had the Text Formatting toolbar available and the cell highlighting feature.
[Automated Action] NeedInfo-To-Unconfirmed
Thank you for reporting the bug. Please attach a sample document, as this makes it easier for us to verify the bug. (Please note that the attachment will be public, remove any sensitive information before attaching it. See https://wiki.documentfoundation.org/QA/FAQ#How_can_I_eliminate_confidential_data_from_a_sample_document.3F for help on how to do so.) I have set the bug's status to 'NEEDINFO'. Please change it back to 'UNCONFIRMED' once the requested document is provided.
This is invalid bug report because it requests support and tells a personal story with different issues, instead of reporting a single reproducible issue, after a search confirms it wasn't reported before. You didn't mention you tried to reset a profile. I'll close. Please search for existing bugs and if not found report separately. Or single out here one reproducible issue and set back Unconfirmed.