mirror of https://github.com/fltk/fltk
96 lines
3.5 KiB
HTML
96 lines
3.5 KiB
HTML
<HTML>
|
|
<HEAD>
|
|
<TITLE>10 - Advanced FLTK</TITLE>
|
|
</HEAD>
|
|
<BODY>
|
|
|
|
<H1 ALIGN="RIGHT"><A NAME="advanced">10 - Advanced FLTK</A></H1>
|
|
|
|
<P>This chapter explains advanced programming and design topics
|
|
that will help you to get the most out of FLTK.</P>
|
|
|
|
<H2><A NAME="multithreading">Multithreading</H2>
|
|
|
|
<P>FLTK supports multithreaded application using a locking mechanism based on "pthreads". We do not provide a threading interface as part of the library. However a simple example how threads can be implemented for all supported platforms can be found in <tt>test/threads.h</tt> and <tt>test/threads.cxx</tt>.
|
|
|
|
<P>To use the locking mechanism, FLTK must be compiled with <tt>--enable-threads</tt> set during the <tt>configure</tt> process. IDE-based versions of FLTK are automatically compiled with locking enabled if possible.
|
|
|
|
<P>In <TT>main()</TT>, call <a href="Fl.html#Fl.lock"><TT>Fl::lock()</TT></A> before <A HREF="Fl.html#Fl.run"><TT>Fl::run()</TT></A> or <A HREF="Fl.html#Fl.wait"><TT>Fl::wait()</TT></A> to start the runtime multithreading support for your program. All callbacks and derived functions like <tt>handle()</tt> and <tt>draw()</tt> will now be properly locked:</P>
|
|
|
|
<pre>
|
|
int main() {
|
|
Fl::lock();
|
|
/* run thread */
|
|
while (Fl::wait() > 0) {
|
|
if (Fl::thread_message()) {
|
|
/* process your data */
|
|
}
|
|
}
|
|
}
|
|
</pre>
|
|
|
|
<P>You can now start as many threads as you like. From within
|
|
a thread (other than the main thread) FLTK calls must be wrapped
|
|
with calls to <a href="Fl.html#Fl.lock"><tt>Fl::lock()</tt></a>
|
|
and <a href="Fl.html#Fl.unlock"><tt>Fl::unlock()</tt></a>:
|
|
|
|
<pre>
|
|
Fl::lock(); // avoid conflicting calls
|
|
... // your code here
|
|
Fl::unlock(); // allow other threads to access FLTK again
|
|
</pre>
|
|
|
|
<p>You can send messages from child threads to the main thread
|
|
using <a href="Fl.html#Fl.awake"><tt>Fl::awake(msg)</tt></a>:</p>
|
|
|
|
<pre>
|
|
void *msg; // "msg" is a pointer to your message
|
|
Fl::awake(msg); // send "msg" to main thread
|
|
</pre>
|
|
|
|
<p>You can also tell the main thread to call a function for you
|
|
as soon as possible by using
|
|
<a href="Fl.html#Fl.awake"><tt>Fl::awake(callback, userdata)</tt></a>:</p>
|
|
|
|
<pre>
|
|
void do_something(void *userdata) {
|
|
// running with the main thread
|
|
}
|
|
|
|
// running in another thread
|
|
void *data; // "data" is a pointer to your user data
|
|
Fl::awake(do_something, data); // call something in main thread
|
|
</pre>
|
|
|
|
|
|
<P>FLTK supports multiple platforms, some of them which do not
|
|
allow any other but the main thread to handle system events and
|
|
open or close windows. The safe thing to do is to adhere to the
|
|
following rules for threads on all operating systems:
|
|
|
|
<ul>
|
|
|
|
<li>Don't <tt>show()</tt> or <tt>hide()</tt>anything that contains
|
|
widgets derived from <tt>Fl_Window</tt>, including dialogs, file
|
|
choosers, subwindows or <tt>Fl_GL_Window</tt>s</li>
|
|
|
|
<li>Don't call <tt>Fl::wait()</tt>, <tt>Fl::flush()</tt> or any
|
|
related methods that will handle system messages</li>
|
|
|
|
<li>Don't start or cancel timers</li>
|
|
|
|
<li>Don't change window decorations or titles</li>
|
|
|
|
<li>The <tt>make_current()</tt> method may or may not work well for regular windows, but should always work for <tt>Fl_GL_Window</tt>s to allow for high speed rendering on graphics cards with multiple pipelines</li>
|
|
|
|
</ul>
|
|
|
|
<P>See also:
|
|
<a href="Fl.html#Fl.awake">void awake(void *message)</A>,
|
|
<a href="Fl.html#Fl.lock">void lock()</A>,
|
|
<a href="Fl.html#Fl.thread_message">void *thread_message()</A>,
|
|
<a href="Fl.html#Fl.unlock">void unlock()</A>.
|
|
|
|
</BODY>
|
|
</HTML>
|