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Beginner
Friday, September 23rd 2005, 3:40pm
QT and dynamic link libraries
Hi guys,
I've a short little question about QT in dynamic link libraries (DLL's or shared objects).
Here a little history: Currently I am working on a open-source game which should be high plugable (support of many different modification by simple DLL plugin).
In the game's startup I open a DLL and start a function out of it. This function creates the login widget. After the user has entered his login information I'd like to unload the DLL and go ahead in the main-function and open another widget out of it.
Here are some pieces of code...
int main ( int argc, char **argv )
{
void *handle;
t_functions functions;
QApplication a (argc, argv);
MainWin = new MainWindow ();
functions.Set_Connect = &Set_Connect;
/* open shared object */
handle = dlopen ( "./liblogin.so", RTLD_NOW );
if ( handle == NULL )
{
printf ( "dlopen failed %s\n", dlerror () );
return 1;
}
/* load functions */
Init_t Init = (Init_t) dlsym ( handle, "Init" );
if ( Init == NULL)
{
printf ( "dlsym failed: %s\n", dlerror () );
dlclose ( handle );
return 1;
}
/* give the shared object all functions which are available */
Init ( &functions );
/* load another DLL function */
Login_Window_t Login_Window = (Login_Window_t) dlsym ( handle, "Login_Window" );
if ( Login_Window == NULL)
{
printf ( "dlsym failed: %s\n", dlerror () );
dlclose ( handle );
return 1;
}
/* create login window */
Login_Window ( MainWin );
MainWin->show ();
/* here we go */
a.connect( &a, SIGNAL( lastWindowClosed () ), &a, SLOT( exit () ) );
a.exec ();
// HERE WE GO!!!
/* close the library */
dlclose (handle);
Make_Other_Widget();
return 0;
}
I hope it's almost clear what I did in there and what I'd like to do. How can I tell QApplication to execute again. Because the function Make_Other_Widget() executes but I can't see any widget
Has someone a little hint for me? Or even a solution?
Best Regards
Max
I've a short little question about QT in dynamic link libraries (DLL's or shared objects).
Here a little history: Currently I am working on a open-source game which should be high plugable (support of many different modification by simple DLL plugin).
In the game's startup I open a DLL and start a function out of it. This function creates the login widget. After the user has entered his login information I'd like to unload the DLL and go ahead in the main-function and open another widget out of it.
Here are some pieces of code...
int main ( int argc, char **argv )
{
void *handle;
t_functions functions;
QApplication a (argc, argv);
MainWin = new MainWindow ();
functions.Set_Connect = &Set_Connect;
/* open shared object */
handle = dlopen ( "./liblogin.so", RTLD_NOW );
if ( handle == NULL )
{
printf ( "dlopen failed %s\n", dlerror () );
return 1;
}
/* load functions */
Init_t Init = (Init_t) dlsym ( handle, "Init" );
if ( Init == NULL)
{
printf ( "dlsym failed: %s\n", dlerror () );
dlclose ( handle );
return 1;
}
/* give the shared object all functions which are available */
Init ( &functions );
/* load another DLL function */
Login_Window_t Login_Window = (Login_Window_t) dlsym ( handle, "Login_Window" );
if ( Login_Window == NULL)
{
printf ( "dlsym failed: %s\n", dlerror () );
dlclose ( handle );
return 1;
}
/* create login window */
Login_Window ( MainWin );
MainWin->show ();
/* here we go */
a.connect( &a, SIGNAL( lastWindowClosed () ), &a, SLOT( exit () ) );
a.exec ();
// HERE WE GO!!!
/* close the library */
dlclose (handle);
Make_Other_Widget();
return 0;
}
I hope it's almost clear what I did in there and what I'd like to do. How can I tell QApplication to execute again. Because the function Make_Other_Widget() executes but I can't see any widget
Has someone a little hint for me? Or even a solution?
Best Regards
Max
Friday, September 23rd 2005, 4:15pm
RE: QT and dynamic link libraries
Try this:
But IMO it would be better, if you redesign your application that it starts the main event loop only once.
QPluginLoader?
|
Source code |
1 2 3 4 5 |
... a.connect( &a, SIGNAL( lastWindowClosed () ), &a, SLOT( quit() ) ); a.exec (); ... } |
Quoted
Has someone a little hint for me? Or even a solution?
QPluginLoader?
You can meet me at Qt Centre - The Ultimate Qt Community site.
Friday, September 23rd 2005, 6:19pm
Originally posted by Flubb
The plugin has to be as independent as possible from the main program.
Has someone an idea how I could handle that?
Have ever heard about an interface or about an abstract base class?
You can meet me at Qt Centre - The Ultimate Qt Community site.
Friday, September 23rd 2005, 7:52pm
This is a simple, completely made up, example:
You might want to read "C++ Primer" by Stanley B. Lippman and Josee Lajoie. There is also Bruce Eckel's book available online and here is a really good C++ FAQ.
|
|
Source code |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 |
// Abstract base class (ABC) that defines an login window interface
// this is what you use in your application
class LoginWindowInterface
{
public:
virtual bool authenticate() = 0;
virtual QString login() const = 0;
virtual QString password() const = 0;
};
// this class implements that interface, but it's provided by the plugin
// you don't need any headers in your application to use it
class LoginWindowImpl : public QDialog, public LoginWindowInterface
{
public:
LoginWindowImpl( QWidget *parent ) : QDialog( parent ) { _ui.setupUi( this ); }
bool authenticate() { return (exec() == QDialog::Accepted); }
QString login() const { return _ui.login->text(); }
QString password() const { return _ui.password->text(); }
};
// abstract login window factory --- create login windows
// this is what your plugin returns when you invoke QPluginLoader::instance()
class LoginWindowFactory : public QObject
{
public:
LoginWindowFactory( QObject *parent ) : QObject( parent ){}
virtual LoginWindowInterface * create( QWidget *parent ) = 0;
};
// concrete factory provided by the plugin
class LoginWindowFactoryImpl : public LoginWindowFactory
{
public:
LoginWindowInterface * create( QWidget *parent ) { return new LoginWindowImpl( parent ); }
};
// sample:
QObject *obj = pluginLoader->instance();
if( obj == 0 ) { ... }
LoginWindowFactory *factory = qobject_cast< LoginWindowFactory * >( obj );
if( factory == 0 ) { /* wrong plugin? */ }
LoginWindowInterface *loginWindow = factory->create( this );
if( loginWindow->authenticate() ) {
QString login = loginWindow->login();
QString password = loginWindow->password();
...
}
else {
/* authentication was cancelled by the user */
}
|
You can meet me at Qt Centre - The Ultimate Qt Community site.
Friday, September 23rd 2005, 7:55pm
Originally posted by Flubb
I googled a lot around and finally I found out, that I can't use interfaces, because I'd like to use signals and slots also.
I don't see any problem in using signals and slots with plugins. Could you post a link to that site?
Or running procedual code after closing a specific widget (outside of the library).
Does this widget happen to be a modal dialog?
You can meet me at Qt Centre - The Ultimate Qt Community site.