[Lazarus] Bug? Form (in design mode) shrinks every time i click on a component in the palette

[Kostas Michalopoulos]

So i have this weird problem under Linux with the GTK2 backend (it doesn't
happen in the Qt backend): every time i click on a component button in the
palette, the designed form shrinks a bit (about 30 pixels or so). This
happens in the stable 1.2 version, 1.4RC and trunk. Deleting ~/.lazarus etc
doesn't fix it so it isn't a settings issue.

I tried to debug it a bit by adding breakpoints in SetBounds, DoOnResize,
etc but couldn't find where the resize request comes from (OnResize stuff
comes from a "WM" message). What is even more weird, commenting out the
OnClick code in the component palette so that it isn't handled at all,
still causes it - i suspect some weird combination of GTK+ events might
cause it since the buttons are still pressed. Although TBH this was mostly
"shooting blind" trying to find some clue.

The only thing i suspect is the window manager i'm using, Window Maker,
might not support some of the more recent window hint/style/etc stuff
(although i'm using the latest version and is in active development since a
few years now). Steam also seems to have trouble with interacting with
wmaker, but that one implements its own widgets and it might be a bug they
didn't bother to fix. Every other program i've tried seems to work fine
with wmaker so i'm not sure if it is that (and besides it works fine with
the Qt backend).

Does anyone have any idea what might cause this and how to fix it (no,
replacing wmaker isn't an option :-P besides if it is a bug there i'll just
fix wmaker)?
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