FLTK Ada Binding

Git repository: Link
Estimated status: 80% complete

16/12/2022

Another year, another lot of bugfixes. Well actually the timing is pure coincidence, but it sounds kinda nice when I put it that way.

• The Get_Value functions for Float_Input and Integer_Input widgets now won't crash if the widget contains an empty string.
• Menu widgets have had their internals reworked to properly take into account the extra Menu_Item generated by adding a submenu to the widget.
• Popup and Pulldown subprograms in Menu widgets now return an Index value instead of a reference to a Menu_Item. This allows them to return a "Not Found" value without using any exceptions.
• Key bindings in Text_Editor widgets now bind properly again.
• Selection related subprograms for Text_Buffers now ensure that out mode parameters keep their values in bounds.

The most vexing thing about all this is that some of the above fixes were needed due to my own oversights, and some were needed due to FLTK changing in subtle ways in the few point releases it has had since I made this binding. And I cannot tell which is which.

9/11/2021

A few noteworthy bugfixes have been applied to the binding.

First, unbeknownst to me the Fl_Widget constructor doesn't copy the given label string inside FLTK and merely stores a pointer. This meant that declaring several Widgets in a row each with their own different label could have unexpected and erratic results. Easily fixed by ensuring the binding constructor also calls copy_label() afterwards.

And second, somehow I had made an oversight with the type assigned to Color, using a signed Integer when it really needed an unsigned modular type with 32 bits of range. Again, easily fixed but even more annoying since it was my fault to begin with.

I'm sure the other guy aside from me who takes an interest in this binding will be happy about these. You know who you are.

21/5/2018

This binding is now complete enough for most purposes. It certainly took more effort than expected, in part due to underestimation of how much needed binding. The vast majority of useful classes are now usable in Ada, with a few exceptions such as the Fl_Browser, Fl_Help_View, Fl_Table, and Fl_Tree widgets.

Noteworthy features and modifications include:

• Constructors are not primitive operations and are not inherited
• Additional types have been defined and used to clean up the API
• No heap allocation/deallocation necessary
• Ada 2012 iterators are implemented for Group and Menu widgets
• The API for Menu and Menu_Item has been rearranged to better reflect a container/item dichotomy
• The Draw and Handle widget methods are easily overridable
• Static methods from the base Fl.H header have been split up into multiple packages
• Automatic addition of widgets to a Group with fl_group_begin and fl_group_end is not supported

A mapping of what C++ headers and methods correspond to what Ada packages, functions, and procedures is included. Also, the below "Hello world" code sample has been modified to work with the updated binding.

25/6/2017

FLTK, or by its full name the Fast Light Toolkit , is a graphical widget toolkit noteworthy for being so lightweight that it is commonly statically linked. Projects that make use of it include the Dillo web browser, the FLWM X window manager, and the Equinox Desktop Environment. There are bindings for it in several languages, including Python, Perl and Ruby, but not Ada. Until now!

This is a spinoff from Adapad, and so despite not yet being complete it can be at least guaranteed to be enough to write a text editor. It's a thick, loosely coupled binding, accomplished by first exporting the interface to C, then importing that to Ada. Attempted usage of the internal C interface as a binding on its own is not supported.

A typical FLTK Hello World program in Ada:

Aside from reworking the types to better fit the strongly typed philosophy of Ada, the entire library has been structured to avoid explicit heap usage. As you can see from the above example, the intended use is to declare FLTK objects on the stack. Allocation and deallocation of the C++ internals is handled automatically.

A few other minor changes were involved, such as requiring widgets to be explicitly added to a group rather than implicitly being added to the last group not yet ended. At the moment the package specifications should provide sufficient information to allow programmers to work with the library.