I recently came across an issue where my window would freeze after some time. I thought it would have something to do with the output widget, which I recently switched from Fl_Text_Display to Fl_Browser (I had not seen this issue before). When I commented out the line that adds lines to the browser, the issue does not appear.

Things that are broken:

Nothing updates, including button press/unpress, scroll bars, check boxes, and text input.

Things that are not broken:

Buttons still seem to work? When I pressed one of the buttons which triggers another window to open, the window still opened. However, the main window was still frozen. The new window is not frozen.

Redrawing the window does not fix the issue, however hiding and showing the window does. The issue also does not always appear, but does most of the time.

My setup is as follows:

The main thread outputs some lines then has Fl::run, then when a certain button is pressed, a new thread is created and detached. The new thread runs some other calculations but outputs sometimes by calling the output function. The output function uses Fl_Browser::add, and adds lines in a format like this:  @S14@C88@.text   . I suspect it has something to do with multithreading, as the issue does not happen in the main thread.

Any help is appreciated.