Re: widget array

[adlaib <adlaib lucent com>]

> fine but  the compiler warns about incompatible pointer type for the gtk_label_set().
instead of:
>  gtk_label_set(*((GtkWidget **)widgetPtr), "changed 1st label");
u need to do: 
gtk_label_set(GTK_LABEL(*((GtkWidget **)widgetPtr)), "changed 1st label");
to make gtk think it's a label widget ptr (which it actually is - cause u have
it pointing 
to a label)

however, there are more pressing matters to attend to - u have
>  *((GtkWidget **)widgetPtr +1)
this is a core dump waiting to happen. on 32 bit machines pointers are 4 bytes
so
it should be + 4; it is much easier (and safer/portable) to do +
sizeof(widgetPtr) - which
should give u the pointer size in bytes.

there were comments about using an array[], if you are doing this from main 
(i assumed u were not) or if the array were global then the array[] would work. 
alternatively, u could define a struct with an array element and malloc the 
struct and pass a ptr to the struct around if u dont like messing with the
pointers

there were also comments about using structures only. it's your code and your
choice. i 
will say that some designs lend themselves to arrays rather than structures, 

ie: 
a window with N labels that you want to do the same kind of processing with -
seems easier
to me to stuff them in an array and do your processing in a loop rather than
using a struct,
- if N is large and u r using a struct, your fingers are gonna bleed from all
that typing...






ksteen@earthlink.net wrote:
> 
> adlaib wrote:
> 
> > oh yeah.
> >
> > just cast the array
> > ie:
> > ---------------------------------------------------------------------------------------
> > int     i;
> > gpointer widgetPtr;
> > gpointer tempWidgetPtr;
> >
> > widgetPtr = (gpointer)malloc(sizeof(widgetPtr)*NUM_WIDGETS);
> >
> > //use tempWidgetPtr to traverse the array,
> > tempWidgetPtr = widgetPtr;
> >
> > // i guess u can write a macro for the typecast
> > for (i=0; i<NUM_WIDGETS; i++) {
> >         *((GtkWidget **)tempWidgetPtr) = gtk_CREATE_SOME_KIND_OF_WIDGET();
> >         DO_SOME_WIDGET_PROCESSING(*((GtkWidget **)tempWidgetPtr));
> >         tempWidgetPtr=+ sizeof(tempWidgetPtr);
> > }
> >
> > //u don't need a cast here cause widgetPtr is already a gpointer.
> > gtk_signal_connect(GTK_OBJECT(THE_WIDGET_THAT_GENERATES_THE_SINGAL),
> > "THE_SIGNAL",
> >                         GTK_SIGNAL_FUNC(THE_SIGNAL_HANDLER), widgetPtr);
> > ---------------------------------------------------------------------------------------
> >
> > THE_SIGNAL_HANDLER() - should destroy all NUM_WIDGETS (depending on what u r
> > doing) and
> > free widgetPtr - if nobody else needs it or else youre gonna have some nasty
> > memory leaks.
> >
> > what i do is define a stucture of several ptrs, malloc the stuct - and pass the
> > structPtr to the signal handler - that way i can do many arrays of widgets at
> > the
> > same time.
> >
> > widgetArray[NUM_WIDGETS] willl NOT work... (unless u declare it static - yuck)
> >
> > hope that helps...
> >
> >
> 
>     Thanks.  That works.  When I tryed It in the simple program below The program runs


> Can  it be written  so that it will compile cleanly?
> 
> #include<stdlib.h>
> #include <gtk/gtk.h>
> 
> void button_click(GtkWidget *widget, gpointer data);
> #define NUM_WIDGETS 2
> 
> int main (int argc, char *argv[])
> {
>   GtkWidget *window;
>   GtkWidget *vbox;
>   GtkWidget *button;
>   gpointer widgetPtr;
> 
>   gtk_init (&argc, &argv);
> 
>   widgetPtr = (gpointer)malloc(sizeof(widgetPtr)*NUM_WIDGETS);
>   window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
>   gtk_widget_show (window);
>   gtk_signal_connect(GTK_OBJECT(window), "delete_event",
>     GTK_SIGNAL_FUNC(gtk_main_quit), NULL);
> 
>   vbox = gtk_vbox_new(FALSE, 0);
>   gtk_widget_show(vbox);
>   gtk_container_add(GTK_CONTAINER(window), vbox);
> 
>   *((GtkWidget **)widgetPtr) = gtk_label_new("Initial label");
>   gtk_widget_show(*((GtkWidget **)widgetPtr));
>   gtk_box_pack_start(GTK_BOX(vbox), *((GtkWidget **)widgetPtr), TRUE, TRUE, 0);
> 
>   *((GtkWidget **)widgetPtr +1) = gtk_label_new("second label");
>   gtk_widget_show(*((GtkWidget **)widgetPtr +1));
>   gtk_box_pack_start(GTK_BOX(vbox), *((GtkWidget **)widgetPtr +1), TRUE, TRUE, 0);
> 
>   button = gtk_button_new_with_label("Change Label");
>   gtk_widget_show(button);
>   gtk_box_pack_start(GTK_BOX(vbox), button, TRUE, TRUE, 0);
>   gtk_signal_connect(GTK_OBJECT(button), "clicked",
>     GTK_SIGNAL_FUNC(button_click), widgetPtr);
> 
>   gtk_main ();
>   return 0;
> }
> 
> void button_click(GtkWidget *widget, gpointer widgetPtr){
> 
>  gtk_label_set(*((GtkWidget **)widgetPtr), "changed 1st label");
> // Compiler warning about incompatible pointer types for arg 1
>  gtk_label_set(*((GtkWidget **)widgetPtr +1), "New second label");
> 
> }
> 
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