90 lines
2.9 KiB
HTML
90 lines
2.9 KiB
HTML
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<HTML>
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<HEAD>
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<TITLE>10 - Advanced FLTK</TITLE>
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</HEAD>
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<BODY>
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<H1 ALIGN="RIGHT"><A NAME="advanced">10 - Advanced FLTK</A></H1>
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<P>This chapter explains advanced programming and design topics
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that will help you to get the most out of FLTK.</P>
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<H2><A NAME="multithreading">10.1 Multithreading</H2>
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<P>FLTK supports multithreaded application using a locking mechanism
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based on "pthreads". We do not provide a threading interface
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as part of the library. However a simple example how threads can
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be implemented for all supported platforms can be found in
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<tt>test/threads.h</tt> and <tt>test/threads.cxx</tt>.
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<P>To use the locking mechanism, the command line version of FLTK
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must be compiled with <tt>--enable-threads</tt> set during the
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<tt>configure</tt> process. IDE-based versions of FLTK are
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automatically compiled with locking enabled if possible.
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<P>In <TT>main()</TT>, before calling <TT>Fl::run()</TT>, call
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<TT>Fl::lock()</TT>. This will startup the runtime multithreading
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support for your program. All callbacks and derived functions
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like <tt>handle()</tt> and <tt>draw()</tt> will now be properly
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locked.
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<pre>
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main() {
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<a href="Fl.html#Fl.lock">Fl::lock()</a>;
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/* run thread */
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while(Fl::wait() > 0) {
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if(<a href="Fl.html#Fl.thread_message">Fl::thread_message()</a>) {
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/* process your data */
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}
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}
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}
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</pre>
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<P>You can now start as many threads as you like. From within
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a thread (other than the main thread) FLTK calls must be wrapped
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in the following code:
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<pre>
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<a href="Fl.html#Fl.lock">Fl::lock()</a>; // avoid conflicting calls
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... // your code here
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<a href="Fl.html#Fl.unlock">Fl::unlock()</a>; // allow other threads to access FLTK again
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<a href="Fl.html#Fl.awake">Fl::awake(msg)</a>; // tells FLTK that another thread has made changes
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</pre>
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<P>FLTK supports multiple platforms, some of them which do not
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allow any other but the main thread to handle system events and
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open or close windows. The safe thing to do is to adhere to the
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following rulesi for threads on all operating systems.
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<ul>
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<li>don't <tt>show()</tt> or <tt>hide()</tt>anything that contains
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widgets derived from <tt>Fl_Window</tt>, including dialogs, file
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choosers, subwindows or <tt>Fl_GL_Window</tt>s</li>
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<li>don't call <tt>Fl::wait()</tt>, <tt>Fl::flush()</tt> or any
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related methods that will handle system messages</li>
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<li>don't start or cancel timers</li>
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<li>don't change window decorations or titles</li>
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<li><tt>make_current()</tt> may or may not work well for regular
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windows, but should always work for <tt>Fl_GL_Window</tt>s to
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allow for high speed rendering on graphics cards with multiple
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pipelines</li>
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</ul>
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<P>See also:
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<a href="Fl.html#Fl.lock">void lock()</A>,
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<a href="Fl.html#Fl.unlock">void unlock()</A>,
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<a href="Fl.html#Fl.awake">void awake(void *message)</A>,
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<a href="Fl.html#Fl.thread_message">void *thread_message()</A>.
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</BODY>
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</HTML>
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