Inconsistent behavior in Gtk Images

[Brian Clark <bc viz tamu edu>]

I had my program working so that I would load an image, display it, and 
make changes to the image.  When I right clicked on the image, it would 
change to the previous image, then back to the current image when I 
released the right mouse button.  This worked fine for quite some time. 
 Then I recently changed some code, though I don't believe I touched 
the code affecting this, and the right click no longer changes the 
image.  I have put cout's in my functions to know that the appropriate 
functions are being called, and they are.

The only two things I can think are this:  Either my method of setting 
the pixbuf is not valid, and I've just been getting lucky to have it 
work so far, or something is happening so that the secondary pixbuf is 
getting loaded with the first pixbuf.  Of course, I can't see where or 
how that happens.  I'm also open to other explanations.

Does anyone have any thoughts?  Beuller?  Beuller?  Beuller?

The GdkPixbufs get set up the first time in the code below.  From then 
on, the buffers that fill them get modified, and that has been enough 
to change the image in the past (in fact, it still works for the 
primary buffer).  I have also tried explicitly setting the pixbufs 
again (one way was to just comment out the "if (firsttime)" line (JUST 
that line) at the end of prepDisplay() just above the return, so that 
the block of code is no longer encapsulated as an "if" statement and 
therefore always runs.

GdkPixbuf* Image::prepDisplay()
{
    int r,g,b;
    int firsttime=0;
    if (NULL==gtkbuffer)    // gtkbuffer initialized to NULL in 
constructor
    {
        gtkbuffer = g_new(guchar,3*width*height);
    }
    if (NULL==gtkbuffer2)   // gtkbuffer2 initialized to NULL in 
constructor
    {
        gtkbuffer2 = g_new(guchar,3*width*height);
        firsttime=1;
    }

    for (int j=(height-1);j>=0;j--)
    {
        for (int i=0;i<width;i++)
        {
            r = (int)(0.5 + pixels[i][j].r);
            g = (int)(0.5 + pixels[i][j].g);
            b = (int)(0.5 + pixels[i][j].b);
        
            if (firsttime)  // put same thing in both buffers if first time
            {
                gtkbuffer2[(i*3+0)+(width*j*3)] = (guchar)r;
                gtkbuffer2[(i*3+1)+(width*j*3)] = (guchar)g;
                gtkbuffer2[(i*3+2)+(width*j*3)] = (guchar)b;
            }
            else  // put gtkbuffer values in gtkbuffer2 if not first time
            {
                gtkbuffer2[(i*3+0)+(width*j*3)] = gtkbuffer[(i*3+0)+(width*j*3)];
                gtkbuffer2[(i*3+1)+(width*j*3)] = gtkbuffer[(i*3+1)+(width*j*3)];
                gtkbuffer2[(i*3+2)+(width*j*3)] = gtkbuffer[(i*3+2)+(width*j*3)];
            }
            gtkbuffer[(i*3+0)+(width*j*3)] = (guchar)r;
            gtkbuffer[(i*3+1)+(width*j*3)] = (guchar)g;
            gtkbuffer[(i*3+2)+(width*j*3)] = (guchar)b;
        }
    }
    if (firsttime)
    {
	primary = gdk_pixbuf_new_from_data(gtkbuffer,GDK_COLORSPACE_RGB, 
FALSE, 8, width, height, width*3, NULL, NULL);
	secondary = gdk_pixbuf_new_from_data(gtkbuffer2,GDK_COLORSPACE_RGB, 
FALSE, 8, width, height, width*3, NULL, NULL);
    }
    return primary;
}

Here are my callbacks.  I've tried putting cout's in the if statements 
to confirm that it's getting the callback and it's getting the right 
button.


gboolean mouse_release_on_image(GtkWidget *window, GdkEventButton 
*event, gpointer user_data)
{
    Image *theImage;
    theImage = (Image*)user_data;
    gint whichButton = event->button;

    if (3==whichButton)
    {
	gtk_image_set_from_pixbuf (GTK_IMAGE(theImage->window), 
theImage->getPrimary());
    }

    return TRUE;
}

gboolean mouse_press_on_image(GtkWidget *img, GdkEventButton *event, 
gpointer user_data)
{
    Image *theImage;
    theImage = (Image*)user_data;
    gint whichButton = event->button;
    GdkPixbuf *temp;

    if (3==whichButton)
    {
        temp = theImage->getSecondary();
        gtk_image_set_from_pixbuf (GTK_IMAGE(theImage->window), temp);
    }

    return TRUE;
}

GdkPixbuf* Image::getSecondary()
{
    return secondary;
}

The function getPrimary() is the same as getSecondary(), with the 
obvious change that it returns primary instead of secondary.
I also tried cout << getPrimary() << ", " << getSecondary() to see if I 
was getting the same address, and I got different numbers (though I may 
not be getting what I think I'm getting--I'm not 100% sure that this 
should work).

It's been making me crazy for 24 hours, now.  If you don't have the 
answer, I'd even happily take the random long shot.

Thanks,
Brian