Progessive zooming and some other small problem.

[Roberto Moral <roberto quantiva com>]

Hello all,

I am trying to get a panel with progressive zomming working, like OS X
dock but with gtk (I bet I am not the first one) I have a function that
populates the panel and assign the event.

Basically I create an event box (docklet), create an image (image) out
of a pixmap and put it inside the container (docklet) then I connect the
signals:

        g_signal_connect(G_OBJECT(docklet),
"enter_notify_event",(GCallback)zoomin, image);
        g_signal_connect(G_OBJECT(docklet),
"leave_notify_event",(GCallback)zoomout, image);
        g_signal_connect(G_OBJECT(docklet), "button_press_event",
(GCallback)launchapp, application);

my zoomin callback looks like this:

static void zoomin(GtkWidget *widget, GdkEventButton *event, gpointer
data) {
        int steps, step_size, i, zoom_width, zoom_height;
/*      GdkImage *image = data; */
        GdkPixbuf *zoomer;

        if (debug) {
        g_print("We are zooming in\n");
}
        steps = 8;
        step_size = 8;
        zoom_width = 64;
        zoom_height = 64;
        
        
        for ( i = 0; i < steps ; i++ ) {
                zoomer = gdk_pixbuf_new_from_data ((gpointer)data, GDK_COLORSPACE_RGB,
TRUE, 8, 64,64, 0, NULL, NULL);
        /*      zoomer = gdk_pixbuf_get_from_image(NULL, image, NULL, -1, -1, 0, 0,
64, 64); */

                zoom_width = zoom_width + step_size;
                zoom_height = zoom_height + step_size;
                usleep(100000);
                gtk_image_set_from_pixbuf(data, gdk_pixbuf_scale_simple(zoomer,
zoom_width, zoom_height, GDK_INTERP_BILINEAR));
                if (debug) {
                        g_print("zoom_width = %d , zoom_height = %d\n", zoom_width,
zoom_height);
                }
        }
}

now to my 2 problems.

first, the zoom works, however it doesn't do the smooth zoom I was
hoping for, it goes from the minimun size to the maximun size altho I
see from the debug that zoom_height and zoom_width are set to the right
values but the image is not being updated. I put the usleep there to
actually see if it was going so fast that I was not able to see the
magnification because of that.

second, I though that gpointer data was a pointer to my GdkImage but
        GdkImage *image = data;
zoomer = gdk_pixbuf_get_from_image(NULL, image, NULL, -1, -1, 0, 0, 64,
64);

result in errors at run time:

(gDock:772): GdkPixbuf-CRITICAL **: file gdk-pixbuf-scale.c: line 235
(gdk_pixbu f_scale_simple): assertion `src != NULL' failed
 
(gDock:772): Gdk-CRITICAL **: file gdkpixbuf-drawable.c: line 1346
(gdk_pixbuf_g et_from_image): assertion `GDK_IS_IMAGE (src)' failed
zoom_width = 72 , zoom_height = 72


and if I try to use the zoomer = gdk_pixbuf_new_from_data
((gpointer)data, GDK_COLORSPACE_RGB, TRUE, 8, 64,64, 0, NULL, NULL);
when the zoom actually occurs I get a corrupted image, grey background
with vertical color lines.


for the first problem I could write the function so it only magnifies
one step at the time, but that would take a toll in the CPU that I am
trying to avoid.
for the second problerm I am sure it is something that I am doing wrong
in both cases.

Could someone give me a pointer as to what I am doing wrong.

Thank you.

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