[fltk.general] API access to FLTK app

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API access to FLTK app Rob McDonald 22:53 Jan 14 top right image
  Apologies for a long setup to what may be an elementary question.

My FLTK interactive program also has a C++ API that we use SWIG to generate wrappers to call from Python and other scripting languages.

When launched normally, a small main() handles some command line options, displays the initial windows, and starts the FLTK event loop.

When called from the API (say Python), an instance of the main data structures is loaded into memory, and calls are made from Python as needed -- no event loop.  In fact, we usually use the API from a binary that does not have any GUI, OpenGL, or FLTK code compiled or linked in.

All the complex data 'lives' in the C++ side of things.  We only pass relatively simple data back and forth through the API.  All significant program state remains on the C++ side.

We would like to be able to launch an interactive GUI from Python that allows the user to interact with the program at the same time Python is interacting.  My program is single threaded and was not designed with thread safety in mind.

To do this, I think we need to...

Add a StartGUI() routine to the API that will start a new thread, open the default GUI windows, and start the event loop (basically do what main() does for the interactive program).  The original thread will return control to Python.

Add a lock that prevents truly simultaneous access.  Whenever an event comes in, FLTK must acquire the lock before calling into my code to handle the event.  Once the event is fully handled (and control returns to the event loop), the lock is released.

At the same time, every API call must acquire the lock before doing anything.  The lock will be released when the API call is finished.

Acquiring the lock will be blocking -- whether from the GUI or the API, if the program is busy, you'll see some lag or hesitation.  However, much of the time, you will be able to interact normally with the program.

Is this the right idea?  Do I have a fundamental misunderstanding here?  Can anyone point at an example application that takes this approach?

Thanks in advance for any help,

Rob



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