See comment 14 (excerpt):
"The current implementation basically handles add_timeout() the same
way as repeat_timeout(), i.e. add_timeout() *calls* repeat_timeout().
However, repeat_timeout() intentionally *corrects* the timeout value
by the value found in the global variable 'missed_timeout_by' which
is set when the timer expires, directly before the timer callback
is called. This variable is never reset."
This commit resets the variable as necessary in Fl::add_timeout().
** This FLTK repository is now our official source code repository. **
WHAT IS FLTK?
The Fast Light Tool Kit ("FLTK", pronounced "fulltick") is a
a cross-platform C++ GUI toolkit for UNIX(r)/Linux(r) (X11),
Microsoft(r) Windows(r), and MacOS(r) X. FLTK provides
modern GUI functionality without the bloat and supports 3D
graphics via OpenGL(r) and its built-in GLUT emulation. It
was originally developed by Mr. Bill Spitzak and is
currently maintained by a small group of developers across
the world with a central repository in the US.
For more information see file README.
35a3e7cc16