Performance improvement for LOTS

[bjoernranft]

Hello,

since lots moved from 18.1.x to 18.2.x also the UI moved from Java Controls to the LibreOffice-Sidebar (and therefore switched to LibreOffice Controls).
The build up of the UI could be improved with templates with a formular UI and many Tabs and Controls it's noticeable.

After some checks with Performance Analyzers and measuring methods it's "calcAdjustedSize(new Size(rect.Width, height));" where it is worth taking a closer look at possible optimizations.

In addition at the moment all controls which are referenced to a tab are loaded at startup, another possible solution or extra performance improvement could be to just show only controls which are in the first or standard definied tab (the tab that the user sees first) and trying to load the currently not visible controls in a background worker that doesn't block.

Regards,

Björn