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git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@5700 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
95 lines
3.6 KiB
HTML
95 lines
3.6 KiB
HTML
<HTML>
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<TITLE>10 - Advanced FLTK</TITLE>
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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">Multithreading</H2>
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<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>.
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<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.
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<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>
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<pre>
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int main() {
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Fl::lock();
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/* run thread */
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while (Fl::wait() > 0) {
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if (Fl::thread_message()) {
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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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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>:
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<pre>
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Fl::lock(); // avoid conflicting calls
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... // your code here
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Fl::unlock(); // allow other threads to access FLTK again
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</pre>
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<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>
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<pre>
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void *msg; // "msg" is a pointer to your message
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Fl::awake(msg); // send "msg" to main thread
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</pre>
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<p>These messages can be read by the main thread using <A HREF="Fl.html#Fl.thread_message"><TT>Fl::thread_message()</TT></A> or by registering a message callback with <A HREF="Fl.html#Fl.set_awake_cb"><TT>Fl::set_awake_cb()</TT></A>:</p>
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<pre>
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void message_cb(void *msg) {
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... do something with "msg" ...
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}
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int main() {
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Fl::lock();
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Fl::set_awake_cb(message_cb);
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/* run thread */
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return (Fl::run());
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}
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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 rules 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>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>
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</ul>
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<P>See also:
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<a href="Fl.html#Fl.awake">void awake(void *message)</A>,
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<a href="Fl.html#Fl.lock">void lock()</A>,
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<a href="Fl.html#Fl.set_awake_cb">void set_awake_cb(void (*cb)(void *)</A>,
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<a href="Fl.html#Fl.thread_message">void *thread_message()</A>,
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<a href="Fl.html#Fl.unlock">void unlock()</A>.
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