Re: Threads (WAS: RE: pthreads, pixmaps and event boxes : update lock s app BUT no-update frees app.)

[flatmax <flatmax cse unsw EDU AU>]

Because the programmer knows precisely which function is run by the thread
! In this threaded function, all calls/functions/methods which use gtk_*
functions are wrapped by these threads_enter/leave functions .... failure
to do so will not stop the thread from running, but will stop the updating
of the widgets correctly.

Matt

On Thu, 15 Mar 2001, Michael Mitton wrote:

> Maybe someone could fill me in here.
>
> Is it possible (from a theoretical standpoint) for the gtk to automatically
> call gdk_threads_enter() and gdk_threads_leave()?  I just never understood
> why the programmer had to make these calls...
>
> -Michael
>
> -----Original Message-----
> From: flatmax [mailto:flatmax cse unsw EDU AU]
> Sent: Thursday, March 15, 2001 12:55 PM
> To: gtk-app-devel-list gnome org
> Subject: Re: pthreads, pixmaps and event boxes : update locks app BUT
> no-update frees app.
>
>
> OK it turns out these errors were created by incorrect useage of the :
> gdk_threads_enter();
> gdk_threads_leave();
> functions.
>
> When threading, these functions SHOULD ONLY BE USED in the thread function
> !
>
> Matt
>
> On Thu, 15 Mar 2001, flatmax wrote:
>
> > Here is the little problem (cited below) ... I wonder if it solvable by
> > hooking more 'gtk_widget_add_events' functions onto the event boxes ?
> >
> > Firstly I have constructed some custom pixmap event boxes using the
> following :
> > GtkPixmap **digitsGtk; // The digit GtkPixmaps
> > GtkWidget **digitsEventBox; // The event box for handling mouse presses
> > Where I use :
> gtk_container_add(GTK_CONTAINER(digitsEventBox[i]),GTK_WIDGET(digitsGtk[i]))
> ;
> > To load the pixmaps into the event boxes.
> >
> > The following function lets the user interact with the event boxes and
> > hence switch the pixmaps :
> >   void eventSetup(void){
> >     for (int i=0; i<digitCnt();i++){
> >       gtk_widget_add_events(GTK_WIDGET(digitsEventBox[i]),
> >                             GDK_BUTTON_RELEASE_MASK);
> >       gtk_signal_connect (GTK_OBJECT(digitsEventBox[i]),
> >                           "button-release-event",
> >                           GTK_SIGNAL_FUNC(digitPress), this);
> >     }
> >   }
> >
> >
> > During app operation either I have the choice of :
> > a] updating digit pixmaps during thread operation, but may not interact
> >    with the pixmap event boxes
> > b] No updating of the digit pixmaps by the thread during
> >    thread operation, but may interact blindly with the pixmap event boxes
> >    (blindly 'cause they aren't being updated !)
> >
> > 'a]' is accomplished by REMOVING the gdk_threads_enter() and
> >      gdk_threads_leave() update lockouts from the 'update' routine.
> > 'b]' is accomplished by INCLUDING the gdk_threads_enter() and
> >      gdk_threads_leave() update lockouts in the 'update' function routine.
> >
> > The update function looks something like so :
> >   void update(void){
> >     for (int i=0;i<digitCnt();i++){
> >       int which=/*digit value*/
> >       cout<<"Threads enter "<<i<<endl;
> >       gdk_threads_enter();
> >
> >       cout<<"Set pixmap"<<endl;
> >       gtk_pixmap_set(digitsGtk[i], digitsGdk[which], digitsMasks[which]);
> >
> >       cout<<"Threads exit"<<endl;
> >       gdk_threads_exit();
> >     }
> >   }
> >
> > thanks
> > Matt
>
>
>
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