<s>
Fast	B-Language
Light	I-Language
Toolkit	I-Language
(	O
FLTK	B-Language
,	O
pronounced	O
fulltick	O
)	O
is	O
a	O
cross-platform	B-Operating_System
widget	O
(	O
graphical	O
control	O
element	O
)	O
library	O
for	O
graphical	B-Application
user	I-Application
interfaces	I-Application
(	O
GUIs	B-Application
)	O
,	O
developed	O
by	O
Bill	O
Spitzak	O
and	O
others	O
.	O
</s>
<s>
Made	O
to	O
accommodate	O
3D	O
graphics	O
programming	O
,	O
it	O
has	O
an	O
interface	O
to	O
OpenGL	B-Application
,	O
but	O
it	O
is	O
also	O
suitable	O
for	O
general	O
GUI	B-Application
programming	O
.	O
</s>
<s>
Using	O
its	O
own	O
widget	O
,	O
drawing	O
and	O
event	O
systems	O
abstracted	O
from	O
the	O
underlying	O
system-dependent	O
code	O
,	O
it	O
allows	O
for	O
writing	O
programs	O
which	O
look	O
the	O
same	O
on	O
all	O
supported	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
FLTK	B-Language
is	O
free	B-License
and	I-License
open-source	I-License
software	I-License
,	O
licensed	O
under	O
GNU	B-Application
Lesser	I-Application
General	I-Application
Public	I-Application
License	I-Application
(	O
LGPL	B-Application
)	O
with	O
an	O
added	O
clause	O
permitting	O
static	B-Library
linking	I-Library
from	O
applications	O
with	O
incompatible	O
licenses	O
.	O
</s>
<s>
In	O
contrast	O
to	O
user	O
interface	O
libraries	O
like	O
GTK	B-Application
,	O
Qt	B-Language
,	O
and	O
wxWidgets	B-Language
,	O
FLTK	B-Language
uses	O
a	O
more	O
lightweight	O
design	O
and	O
restricts	O
itself	O
to	O
GUI	B-Application
functionality	O
.	O
</s>
<s>
Because	O
of	O
this	O
,	O
the	O
library	O
is	O
very	O
small	O
(	O
the	O
FLTK	B-Language
"	O
Hello	O
World	O
"	O
program	O
is	O
around	O
100	O
KiB	O
)	O
,	O
and	O
is	O
usually	O
statically	B-Library
linked	I-Library
.	O
</s>
<s>
It	O
also	O
avoids	O
complex	O
macros	O
,	O
separate	O
code	O
preprocessors	O
,	O
and	O
use	O
of	O
some	O
advanced	O
C++	B-Language
features	O
:	O
templates	O
,	O
exceptions	B-General_Concept
,	O
and	O
run-time	B-Application
type	I-Application
information	I-Application
(	O
RTTI	B-Application
)	O
or	O
,	O
for	O
FLTK	B-Language
1.x	O
,	O
namespaces	O
.	O
</s>
<s>
FLTK	B-Language
offers	O
fewer	O
widgets	O
than	O
most	O
GUI	B-Library
toolkits	I-Library
and	O
,	O
because	O
of	O
its	O
use	O
of	O
non-native	O
widgets	O
,	O
does	O
not	O
have	O
native	O
look-and-feel	O
on	O
any	O
platform	O
.	O
</s>
<s>
FLTK	B-Language
was	O
originally	O
designed	O
to	O
be	O
compatible	O
with	O
the	O
Forms	O
Library	O
written	O
for	O
Silicon	O
Graphics	O
(	O
SGI	O
)	O
machines	O
(	O
a	O
derivative	O
of	O
this	O
library	O
called	O
XForms	B-Application
is	O
still	O
used	O
quite	O
often	O
)	O
.	O
</s>
<s>
This	O
naming	O
was	O
extended	O
to	O
all	O
new	O
methods	O
and	O
widgets	O
in	O
the	O
C++	B-Language
library	O
,	O
and	O
this	O
prefix	O
FL	O
was	O
taken	O
as	O
the	O
name	O
of	O
the	O
library	O
.	O
</s>
<s>
After	O
much	O
debating	O
and	O
searching	O
for	O
a	O
new	O
name	O
for	O
the	O
toolkit	O
,	O
which	O
was	O
already	O
in	O
use	O
by	O
several	O
people	O
,	O
Bill	O
Spitzak	O
came	O
up	O
with	O
Fast	O
Light	O
Tool	O
Kit	O
(	O
FLTK	B-Language
)	O
.	O
</s>
<s>
FLTK	B-Language
is	O
an	O
object-oriented	B-Language
widget	B-Library
toolkit	I-Library
written	O
in	O
the	O
programming	O
language	O
C++	B-Language
.	O
</s>
<s>
While	O
GTK	B-Application
is	O
mainly	O
optimized	O
for	O
the	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
,	O
FLTK	B-Language
works	O
on	O
other	O
platforms	O
,	O
including	O
Microsoft	B-Application
Windows	I-Application
(	O
interfaced	O
with	O
the	O
Windows	B-Library
API	I-Library
)	O
,	O
and	O
OS	B-Operating_System
X	I-Operating_System
(	O
interfaced	O
with	O
Quartz	B-Operating_System
)	O
.	O
</s>
<s>
A	O
Wayland	B-Language
back-end	O
is	O
being	O
discussed	O
.	O
</s>
<s>
FLTK2	B-Language
has	O
gained	O
experimental	O
support	O
for	O
optionally	O
using	O
the	O
cairo	B-Language
graphics	I-Language
library	I-Language
.	O
</s>
<s>
A	O
library	O
written	O
in	O
one	O
programming	O
language	O
may	O
be	O
used	O
in	O
another	O
language	O
if	O
language	B-Application
bindings	I-Application
are	O
written	O
.	O
</s>
<s>
FLTK	B-Language
has	O
a	O
range	O
of	O
bindings	O
for	O
various	O
languages	O
.	O
</s>
<s>
FLTK	B-Language
was	O
mainly	O
designed	O
for	O
,	O
and	O
is	O
written	O
in	O
,	O
the	O
programming	O
language	O
C++	B-Language
.	O
</s>
<s>
However	O
,	O
bindings	O
exist	O
for	O
other	O
languages	O
,	O
for	O
example	O
Lua	B-Language
,	O
Perl	B-Language
,	O
Python	B-Language
,	O
Ruby	B-Language
,	O
Rust	B-Application
and	O
Tcl	B-Operating_System
.	O
</s>
<s>
For	O
FLTK	B-Language
1.x	O
,	O
this	O
example	O
creates	O
a	O
window	O
with	O
an	O
Okay	O
button	O
:	O
</s>
<s>
FLTK	B-Language
includes	O
Fast	O
Light	O
User	O
Interface	O
Designer	O
(	O
FLUID	O
)	O
,	O
a	O
graphical	O
GUI	B-Application
designer	O
that	O
generates	O
C++	B-Language
source	O
and	O
header	O
files	O
.	O
</s>
<s>
Many	O
programs	O
and	O
projects	O
use	O
FLTK	B-Language
,	O
including	O
:	O
</s>
<s>
Agenda	B-Application
VR3	I-Application
,	O
a	O
Linux-based	O
personal	B-Application
digital	I-Application
assistant	I-Application
with	O
software	O
based	O
on	O
FLTK	B-Language
.	O
</s>
<s>
Nuke	B-Language
,	O
a	O
digital	O
compositing	O
program	O
.	O
</s>
<s>
X	B-Application
window	I-Application
managers	I-Application
:	O
</s>
<s>
This	O
version	O
history	O
is	O
an	O
example	O
of	O
the	O
sometimes	O
tumultuous	O
nature	O
of	O
open-source	B-Application
development	I-Application
.	O
</s>
<s>
This	O
was	O
a	O
development	O
branch	O
,	O
long	O
thought	O
to	O
be	O
the	O
next	O
step	O
in	O
FLTK	B-Language
's	O
evolution	O
,	O
with	O
many	O
new	O
features	O
and	O
a	O
cleaner	O
programming	O
style	O
.	O
</s>
