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

[Michael Mitton <Michael Mitton millersville edu>]

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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