Virtual Treeview causes multiple problems in other controls in Lazarus/Cocoa

[MISV]

Here is a demo project which demonstrates multiple issues when having a visuble virtual treeview on Lazarus Mac/Cocoa (using fpcupdeluxe "trunk" which includes newest virtual treeview)

I first reported the issue here: https://bugs.freepascal.org/view.php?id=34002

And together with Lazarus developers narrowed it down to be an issue with virtualtreeview and cocoa.

The attached demo project demonstrates:

1) Toolbuttons becoming invisible until clicked
2) TPageControl tabsheets misdrawn until clicked
3) TEdit looking very weird with black background until clicked
4) Some captions/labels etc. are drawn upside down some places

All only when the two virtual treeviews are set to visible in the project.

...

To see all issues simply
- run project
- doubleclick window title bar (minimizes to dock)
- open from mac dock.