Avoid CSDs rounded corners when no compositor is present

[Carlos Pita <carlosjosepita gmail com>]

Hi all,

I'm not sure whether the following could be addressed at the theme
level or not, but here it goes:

1) People using standalone window managers often dislike or don't care
about running a composite manager.

2) Adwaita is a theme of choice for people that want to keep a
consistent look between gtk2 and gtk3 based apps.

3) Latest releases of gtk include standard dialogs (file open, print,
etc.) based on CSD.

4) If the current theme is Adwaita and no composite manager is
present, CSD dialogs get slightly rounded top borders, which play bad
with the rectangular area of the client (remember: no transparency
available).

I think the most conservative option is to fallback to straight
borders when a composite manager is not available. But I'm not sure
whether the client is rendering the rounded borders or it's more of a
theme issue. I tend to believe it's a theme thing, as far as other
themes don't show the same behavior.

Is it possible to change this in the stock Adwaita theme? If not,
could anyone theme savvy provide some hack to force straight borders
from the user gtk settings?

Best regards
--
Carlos