[Lazarus] Lazarus IDE not sizeable on Raspbian PIXEL

[Bo Berglund]

I don't know if this is a known problem or if there are solutions to
it, but here goes:

I have just completed installing Lazarus 1.6.2 and FPC 3.0.0 on a
pristine Raspbian PIXEL operating system running on an RPi3.

When Lazarus starts up the first time the usual dialog about the fpc
sources pops up but it auto-fills in correctly so I do not have to do
anything. Then the main IDE is shown.

Now the problem:
The main IDE bar on top of the screen only reaches about 60% of the
width of the screen and there is no way to resize it using the mouse.
The other Lazarus windows are resizable in the normal way but not the
main IDE bar. And the maximize button on this top window is also
disabled (grayed out) and cannot be used.

I suspect that this has something to do with the new window manager on
Raspbian PIXEL, and since it has been out for half a year now I am
hoping someone here has a solution to this problem...
Is there some extra dependency I have to install into the operating
system apart from the usual set I always install?
These are the ones I always install before starting the FPC/Lazarus
installation:

libx11-dev libgdk-pixbuf2.0-dev libcairo2-dev gir1.2-coglpango-1.0
libpangox-1.0-dev xorg-dev libgtk2.0-dev libpango1.0-dev

Any ideas welcome!


-- 
Bo Berglund
Developer in Sweden