3x380V

@maxwxyz, I guess 1.0 milestone is a bit too optimistic, let me explain. This is just another approach to #15435, but question remains the same. How should it look like?...

Progress bar is out of scope as there is no way finding where in the start process we are. Some kind of message driven periodic movement is doable, but text...

Thanks for testing this. But there is something to clarify. Total launch time should be almost the same. It is increased by the time needed to render text, which is...

Lets limit this PR to scrolling splash messages as originally intended. I will open another one with splash and about dialog refactoring.

@chennes or whoever will eventually merge this PR: it conflicts with #16438 and I'd like that cleanup to be merged first. Then I rebase this one, resolve conflicts and force...

#16438 is [3x380V:dlgabout](https://github.com/3x380V/FreeCAD/tree/dlgabout) branch based on `main` branch, it does code refactor and cleanup. This is [3x380V:splash](https://github.com/3x380V/FreeCAD/tree/splash) branch based on [3x380V:dlgabout](https://github.com/3x380V/FreeCAD/tree/dlgabout) branch and does implement scrolling messages. Unfortunately I do...

@wwmayer, what is needed to move forward with this PR? Apart from visual appearance, which I cannot cope with. I'd like to use it as a base for indeterminate progress...

The reason I implemented it is to remove 50ms delay after each message printed, so it does not slow down startup. It could be improved by printing errors in different...

- with scrolling area set to single line height, scrolling splash behavior is the same (minus delay). - it is possible to keep important messages; assume error (possibly rendered in...

@yorikvanhavre, unless I'm missing something, it is implemented that way.