[maemo-developers] Dialogs and gtk_window_set_transient_for()

[From: Arto Karppinen]

Tapani Pälli wrote:
> Hello;
>
> ext Arto Karppinen wrote:
>   
>> Hi
>>
>> Im developing an app which shows modal dialogs to the user. Also the app 
>> may popup a custom error message dialog if something goes wrong. 
>> Currently i'm setting both dialog to be transient_for to my main window. 
>> This has the effect of the error dialog appearing beneath the first 
>> modal dialog..
>>
>>   
>>     
> Does the error happen due to a wrong action in the first dialog? 

The error may happen inside a subsystem which the dialog calls.

> Why
> don't you set error dialog to be transient to the modal dialog?
>
>   

Because i have two main windows, and several dialogs for both. The 
subsystem which pops up the error dialog does not have any trivial way 
of figuring out which window happens to be on top at the moment.

>> That is, the dialog which is first set to be trancient for the main 
>> window, is shown on top of any dialog which is created later.
>>
>> Which is not what i want, i want the error message dialog to be shown on 
>> top.
>>
>> Is there some way to get which dialogs are trancient for a window, or do 
>> i have to build some kind of system which keeps track of what dialogs 
>> are currently shown
>>     
>
> If you show a modal dialog, it means that you should not be able to
> access the application elsewhere before closing this dialog. It is
> probably best for you to set error dialog transient to the modal dialog.
> You might want to pass the window as parameter to the function that pops
> up the dialog so it can be changed easily.
>   

All of my dialogs take the parent dialog as a pointer. The problem is of 
scale, i have too many windows to manually write switch case or some 
other structure to select the correct parent from somewhere.

The core of the problem is that Gtk provides 
gtk_window_get_transient_for() function which you can use to iterate 
"upwards" from child windows until you get to the toplevel window.

However, Gtk does not have (as far i know), 
gtk_window_get_transient_children() or some such, which you could use to 
iterate "downwards" from toplevel window until you would reach the child 
which happens to be on top at the moment.

Currently im using g_object_set_data() to set pointer to the child 
window from the parent window so i can iterate "downwards" the window 
tree. This way i only need to know my main window, and i can iterate 
"downwards" from there until i find the dialog on top.

This is what I'm doing for now:

#define IRRECO_DLG_CHILD_DATA_KEY "IrrecoChildDialog"

void irreco_dlg_set_parent(IrrecoDlg *self, GtkWindow *parent)
{
    gint depth = 0;
    gpointer data;
    IRRECO_ENTER
   
    if (gtk_window_get_transient_for(GTK_WINDOW(self))) {
        IRRECO_PRINTF("Dialog is already tracient for something.\n");
        IRRECO_RETURN
    }
   
    /* Iterate trough child windows, until we find the one that is
       topmost on screen. */
    do {
        data = g_object_get_data(G_OBJECT(parent), 
IRRECO_DLG_CHILD_DATA_KEY);
        if (data != NULL && GTK_IS_WINDOW(data)) {
            parent = GTK_WINDOW(data);
        } else {
            break;
        }
        depth++;
    } while (TRUE);
   
    IRRECO_PRINTF("Number of parent dialogs on screen: %i\n", depth);
   
    /* Set self as a child window. */
    gtk_window_set_transient_for(GTK_WINDOW(self), parent);
    g_object_set_data(G_OBJECT(parent), IRRECO_DLG_CHILD_DATA_KEY, self);
   
    /* Set up cleanup event. */
    g_signal_connect(G_OBJECT(self), "destroy",
        G_CALLBACK(irreco_dlg_data_key_cleanup), parent);
    IRRECO_RETURN
}

static void irreco_dlg_data_key_cleanup(IrrecoDlg *self, GtkWindow *parent)
{
    gpointer data;
    IRRECO_ENTER
   
    if (G_IS_OBJECT(parent) == FALSE) IRRECO_RETURN;
   
    /* Does parent have a pointer which points to this instace? */
    data = g_object_get_data(G_OBJECT(parent), IRRECO_DLG_CHILD_DATA_KEY);
    if (data == NULL || data != self) IRRECO_RETURN;
   
    /* Remote the pointer. */
    g_object_steal_data(G_OBJECT(parent), IRRECO_DLG_CHILD_DATA_KEY);
    IRRECO_RETURN
}


-- 
Arto Karppinen
------------------------------
arto.karppinen at iki.fi