Article #362: What is FLTK?

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Article #362: What is FLTK?

Created at 07:59 Jan 29, 2005 by mike

FLTK is a LGPL'd C++ graphical user interface toolkit for X (UNIX®), Linux® (X11 and Wayland), macOS (aka OS X), OpenGL, and Windows (Microsoft® Windows® XP, 2000, and later). FLTK is currently maintained by a small group of developers across the world with a central repository on GitHub and its main website at

Modified by AlbrechtS on 16 Aug 2016 and 05 Apr 2023.

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From wisenwild, 04:52 May 30, 2005 (score=3)

Could you elaborate a little about the rational of this particular GUI toolkit compared to others? Is it intended to be smaller, or more efficient? Why did you guys choose to rewrite a library from scratch instead of using stripped versions of existing libs (GTK, Qt, ...)? My question is very naive but I think some kind of hint about why you started a new project would be useful (There's a lot of GUI projects around and it's not very easy to find to what exact purpose is this or this lib best suited) Thank you
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From mike, 05:47 May 30, 2005 (score=3)

FLTK started life as a replacement for the XForms library and was later ported to Windows and MacOS.  It actually was started before GTK+ and KDE but was not widely available until 1998 when I started hosting the FLTK project.

FLTK (Fast Light Toolkit) is both faster and lighter than other toolkits without sacrificing features. We leverage C++ subclassing for creating and deriving new widgets from existing ones, and use an efficient event handling, drawing, and callback mechanism to respond to input from users and other data sources. We use the core APIs on each platform (X11 for UNIX/Linux, GDI for Windows, Quickdraw/Quartz for MacOS) and build FLTK upon a common "glue layer" API to them. In addition, FLTK is one of the only open source toolkits which natively supports OpenGL rendering - GTK+ and Qt are still quite weak in this area.

We do not depend on text-based attributes (GTK+, Motif), complex chains of support libraries (GTK+, KDE, wxWidgets), workarounds to provide OO features in standard C (GTK+), a special compiler preprocessor (KDE), or a non-standard variant of C (Cocoa).

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From lolke, 01:44 Sep 02, 2005 (score=3)

Comparing to wxwidgets, what would be the major merits of using FLTK, what of using wxwidgets?

Does it integrate well with other libraries (notably boost)

How do you currently support localization?
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