[9297] in The GTK GIMP ToolKit mailing list archive
[gtk-list] gpointer and callbacks
daemon@ATHENA.MIT.EDU (dross)
Wed Oct 14 16:04:35 1998
Date: Wed, 14 Oct 1998 20:08:26 +0000
From: dross <dross@melbpc.org.au>
To: gtk-list@redhat.com
Resent-From: gtk-list@redhat.com
Reply-To: gtk-list@redhat.com
I'm trying to write a simple audio interface, and am setting sliders to
adjust the volume and mic levels. I have a callback function that I would
like to pass an integer identifier, identifing the device I want to change
the level for. The problem is I can't seem to pass an integer to this function.
I am new to gtk and I don't quite understand what a gpointer is, and in all the
examples I found only strings where used. Can you pass any type using gpointer?
void adjust_level (GtkAdjustment * adj, gpointer data)
{
int volume = adj->value, rvolume;
/* equalise left and right channels */
rvolume = (volume & 0x000000ff) << 8;
volume = (volume & 0x000000ff) | rvolume;
if (ioctl (fd_mixer, MIXER_WRITE (*(int*)data), &volume) < 0)
{
perror ("Can't set current volume settings");
}
}
void setup_window (GtkWidget * parent)
{
GtkWidget *vbox, *hbox;
GtkWidget *button;
GtkWidget *hscale;
int volume = 0;
int device, *ptr;
ptr = &device;
.
.
.
/* Set the initial volume to the left chanel */
device = SOUND_MIXER_VOLUME;
volume = get_level(device);
vol_adj = (GtkAdjustment*)gtk_adjustment_new ((volume & 0x000000ff),
0, 100, 1, 1, 0);
hscale = gtk_hscale_new (GTK_ADJUSTMENT (vol_adj));
gtk_signal_connect (GTK_OBJECT (vol_adj), "value_changed",
GTK_SIGNAL_FUNC (adjust_level), (gpointer)&device);
gtk_box_pack_start (GTK_BOX (hbox), hscale, TRUE, TRUE, 0);
gtk_widget_show (hscale);
/* Set the initial volume to the left chanel */
device = SOUND_MIXER_MIC;
volume = get_level(device);
mic_adj = (GtkAdjustment*)gtk_adjustment_new ((volume & 0x000000ff),
0, 100, 1, 1, 0);
hscale = gtk_hscale_new (GTK_ADJUSTMENT (mic_adj));
gtk_signal_connect (GTK_OBJECT (mic_adj), "value_changed",
GTK_SIGNAL_FUNC (adjust_level), (gpointer)&device);
.
.
.
}
Thanks
Darryl Ross
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