<s>
ReAction	B-Library
GUI	I-Library
is	O
the	O
widget	B-Library
toolkit	I-Library
engine	O
that	O
is	O
used	O
in	O
AmigaOS	B-Application
3.2-4.1	O
.	O
</s>
<s>
It	O
is	O
an	O
evolution	O
of	O
ClassAct	B-Library
,	O
which	O
is	O
an	O
object-oriented	B-Language
system	O
of	O
classes	O
that	O
enhanced	O
the	O
aspect	O
of	O
the	O
Workbench	O
2.0	O
GUI	O
of	O
AmigaOS	B-Application
.	O
</s>
<s>
The	O
native	O
Amiga	O
windowing	B-Application
system	I-Application
is	O
called	O
Intuition	B-Application
,	O
which	O
manages	O
the	O
rendering	O
of	O
screens	O
,	O
windows	O
and	O
basic	O
widgets	O
.	O
</s>
<s>
However	O
,	O
until	O
AmigaOS	B-Application
2.0	O
there	O
was	O
no	O
standardized	O
look	B-Application
and	I-Application
feel	I-Application
,	O
and	O
often	O
application	O
developers	O
had	O
to	O
write	O
their	O
own	O
non-standard	O
widgets	O
(	O
both	O
buttons	O
and	O
menus	O
)	O
,	O
with	O
Intuition	B-Application
providing	O
little	O
support	O
.	O
</s>
<s>
Intuition	B-Application
was	O
later	O
enhanced	O
with	O
gadtools.library	O
(	O
AmigaOS	B-Application
2.0	O
and	O
later	O
)	O
,	O
which	O
provides	O
a	O
set	O
of	O
standard	O
widgets	O
.	O
</s>
<s>
AmigaOS	B-Application
2.0	O
also	O
introduced	O
a	O
standard	O
dialog	O
system	O
called	O
ASL	O
(	O
Amiga	O
Standard	O
requester	O
Library	O
)	O
and	O
the	O
Amiga	O
User	O
Interface	O
Style	O
Guide	O
,	O
which	O
defined	O
how	O
applications	O
should	O
be	O
laid	O
out	O
for	O
consistency	O
.	O
</s>
<s>
Intuition	B-Application
was	O
improved	O
with	O
BOOPSI	B-Device
(	O
Basic	O
Object	B-Language
Oriented	I-Language
Programming	I-Language
System	O
for	O
Intuition	B-Application
)	O
which	O
provides	O
an	O
object-oriented	B-Language
interface	O
on	O
which	O
to	O
build	O
an	O
extensible	O
set	O
of	O
widgets	O
.	O
</s>
<s>
The	O
introduction	O
of	O
BOOPSI	B-Device
allowed	O
third-party	O
developers	O
to	O
create	O
comprehensive	O
widget	B-Library
toolkits	I-Library
,	O
such	O
as	O
MUI	B-Library
and	O
ClassAct	B-Library
which	O
later	O
evolved	O
into	O
ReAction	O
.	O
</s>
<s>
ClassAct	B-Library
is	O
an	O
object-oriented	B-Language
system	O
of	O
classes	O
and	O
gadgets	O
developed	O
on	O
the	O
BOOPSI	B-Device
system	O
introduced	O
with	O
AmigaOS	B-Application
2.0	O
.	O
</s>
<s>
ClassAct	B-Library
was	O
modeled	O
after	O
the	O
future	O
direction	O
Commodore	O
had	O
envisioned	O
for	O
the	O
future	O
of	O
the	O
OS	O
presented	O
at	O
Orlando	O
Developers	O
Conference	O
prior	O
to	O
Commodore	O
's	O
Bankruptcy	O
.	O
</s>
<s>
Programmers	O
Christopher	O
'	O
caldi	O
 '	O
Aldi	O
,	O
Timothy	O
Aston	O
,	O
Osma	O
'	O
Tau	O
 '	O
Ahvenlampi	O
came	O
together	O
and	O
ClassAct	B-Library
is	O
a	O
realization	O
of	O
that	O
future	O
.	O
</s>
<s>
Various	O
styles	O
can	O
be	O
applied	O
to	O
ClassAct	B-Library
gadgets	O
,	O
such	O
as	O
3D	O
aspect	O
.	O
</s>
<s>
ReAction	O
is	O
the	O
official	O
AmigaOS	B-Application
GUI	O
builder	O
since	O
the	O
OS	O
3.5	O
days	O
.	O
</s>
<s>
Nowadays	O
it	O
is	O
being	O
built	O
on	O
top	O
of	O
Intuition	B-Application
,	O
updated	O
and	O
has	O
a	O
better	O
and	O
more	O
consistent	O
look	O
through	O
the	O
apps	O
that	O
use	O
it	O
.	O
</s>
<s>
ReAction	O
system	O
of	O
classes	O
and	O
gadgets	O
is	O
almost	O
the	O
same	O
as	O
ClassACT	B-Library
.	O
</s>
<s>
It	O
is	O
expandable	O
and	O
modular	O
as	O
the	O
same	O
as	O
ClassAct	B-Library
.	O
</s>
<s>
via	O
a	O
graphical	O
pie	B-Application
chart	I-Application
.	O
</s>
<s>
There	O
are	O
two	O
main	O
widget	B-Library
toolkits	I-Library
competing	O
in	O
the	O
Amiga	O
world	O
.	O
</s>
<s>
ReAction	O
which	O
is	O
the	O
default	O
GUI	B-Library
toolkit	I-Library
chosen	O
for	O
AmigaOS	B-Application
3.2-4.1	O
and	O
for	O
developing	O
AmigaOS	B-Application
software	O
,	O
and	O
MUI	B-Library
which	O
is	O
the	O
default	O
GUI	B-Library
toolkit	I-Library
chosen	O
for	O
MorphOS	B-Operating_System
.	O
</s>
<s>
AROS	B-Application
uses	O
Zune	B-Library
toolkit	O
which	O
is	O
an	O
open	O
source	O
MUI	B-Library
clone	O
.	O
</s>
<s>
Cygnix	O
is	O
a	O
lightweight	O
UNIX	B-Application
simulation	O
environment	O
for	O
AmigaOS	B-Application
that	O
comes	O
with	O
an	O
X11	B-Operating_System
server	I-Operating_System
Cygwin	B-Language
,	O
and	O
this	O
has	O
been	O
used	O
to	O
port	O
programs	O
such	O
as	O
AbiWord	B-Language
or	O
GIMP	B-Application
to	O
the	O
Amiga	O
.	O
</s>
<s>
A	O
slightly	O
related	O
project	O
is	O
a	O
GTK	B-Application
MUI	B-Library
wrapper	O
which	O
eventually	O
will	O
simplify	O
porting	O
of	O
GTK	B-Application
based	O
software	O
.	O
</s>
<s>
Various	O
multi-platforms	O
graphics	O
libraries	O
and	O
toolkits	O
such	O
as	O
Cairo	B-Language
and	O
SDL	B-Operating_System
are	O
also	O
available	O
on	O
Amiga	O
,	O
and	O
are	O
the	O
basics	O
for	O
creating	O
new	O
and	O
enhanced	O
Toolkits	O
,	O
new	O
GUIs	O
,	O
new	O
systems	O
of	O
widgets	O
,	O
etc	O
.	O
</s>
