When comparing Tk vs FLTK, the Slant community recommends Tk for most people. In the question“What are the best cross-platform GUI toolkits?” Tk is ranked 12th while FLTK is ranked 15th. The most important reason people chose Tk is:
Bindings for Python, C, C++, Ruby, Perl, Go, Java, Haskell and more, see [Languages with a Tk binding](https://wiki.tcl-lang.org/page/Languages+with+a+Tk+binding).
Ranked in these QuestionsQuestion Ranking
Pro Bindings for several languages
Bindings for Python, C, C++, Ruby, Perl, Go, Java, Haskell and more, see Languages with a Tk binding.
Pro Easy Styling
Once you understand how to style, the styling can look great
Pro Great for beginners
Easy to pick up and run with it.
It's simple design and lack of more advanced C++ features makes it easy for beginners.
Uses a limited and lightweight design and restricts itself to solely GUI functionality. Because of this restriction, the FLTK hello world example is only about 100 KiB.
Well-designed widgets, coded with careful attention to rendering/execution speed.
FLTK code developed more than 10 years ago still compiles and runs perfectly, without changes.
Pro GUI designer
Fast Light User-Interface Designer (FLUID) included.
Con Base looks are garbage without a good amount of styling
Going with the base look for your app is a bad idea because it looks like garbage with the defaults
Con C# support lacking
Although the Eagle Project exists, which offers Mono and .NET Core support, C# support is not standard.
Con Can be too simple for some projects
FLTK offers far fewer widgets than most other toolkits.
Con Does not look like a native application
Because it uses non-native widgets, it doesn't look like a native application on any platform.