[Lazarus] TPageControl suddenly stopped working

[David Riley]

On 12/03/2011 06:15 AM, Tail Kinker wrote:
> I am working on a project that has two TPageControl instances.  One is
> embedded inside a TTabSheet of another.  It is the embedded one that
> for whatever stupid reason has stopped working.
>
> This behaviour started after I set one of the TTabSheets in the
> TPageControl disabled, but did not cease after I re-set the TTabSheet
> back to enabled.
>
> Can anyone think what might be causing this behaviour?

I've just encountered this problem after upgrading from Ubuntu 10.04 to
Fedora 16, a tab control raises EInterfaceCritical:
"clearlooks_style_draw_box_gap: assertion 'height >= -1 'failed'".  It
seems the LCL is having some sort of problem with the Clearlooks theme,
which I'd imagine is analouge to the new Gnome-shell "adawaita" theme in
the LCL internals judging by the error messages, and changing the theme
is fixing the problem.  If your issue is similar try chaning your GTK
theme and see if it fixes it.