How to refresh gtk widget (gtk_widget_queue_draw error) - c++

Question

I have a simple gtk window with one image in it. After making some modification on that image (taken from OpenCV) I want to make window refresh by expose-event. I use gtk2 and it is not possible to change to gtk3. There is no errors but image is not redrawn, the old one still persist.
class TestApp {
public:
GtkWidget *frameWindow;
GInputStream *inStr;
GtkWidget *image;
GdkPixbuf *pixBuff;
cv::Mat *frame;
TestApp(int argc, char *argv[]) : frameWindow(NULL), image(NULL), pixBuff(NULL), inStr(NULL),frame(NULL){
gtk_init(&argc, &argv);
}
int refresh(cv::Mat *f){
frame=f;
int sz = f->dataend - f->datastart;
memcpy((uchar*)gdk_pixbuf_get_pixels(pixBuff),f->datastart,sz);
gtk_widget_queue_draw(frameWindow);
return 0;
}
void imshow(cv::Mat *im){
/* main window */
frame = im;
frameWindow = gtk_window_new(GTK_WINDOW_TOPLEVEL);
gtk_container_set_border_width(GTK_CONTAINER(frameWindow), 1);
gtk_window_set_title(GTK_WINDOW(frameWindow), "image");
gtk_window_set_default_size(GTK_WINDOW(frameWindow), 1280, 720);
gtk_window_set_position(GTK_WINDOW(frameWindow), GTK_WIN_POS_CENTER);
gtk_window_fullscreen(GTK_WINDOW(frameWindow));
pixBuff=gdk_pixbuf_new_from_data((guchar*)im->datastart,GDK_COLORSPACE_RGB,FALSE,8,im->size().width,im->size().height,(im->channels()*im->cols), NULL,NULL);
image = gtk_image_new_from_pixbuf(pixBuff);
gtk_container_add(GTK_CONTAINER(frameWindow), image);
g_object_ref_sink(G_OBJECT(frameWindow));
g_signal_connect(G_OBJECT(frameWindow), "expose_event", G_CALLBACK((void*)exposeCb), (gpointer)this);
g_signal_connect(G_OBJECT(frameWindow), "key_press_event", G_CALLBACK((void*)buttonCb), (gpointer)this);
gtk_widget_realize(frameWindow);
gtk_widget_show_all(frameWindow);
gtk_main();
}
static gboolean buttonCb(GtkWidget *eventBox, GdkEventKey *event, gpointer data){
char c = event->keyval;
switch(c){
case 'q':
gtk_widget_destroy(eventBox);
gtk_main_quit();
break;
}
return true;
}
static gboolean exposeCb(GtkWidget *eventBox, GtkWidget *event, gpointer data){
return false;
}
};
int main (int argc, char *argv[]) {
TestApp gtkObj(argc,argv);
cv::Mat im=cv::imread("colour256.png");
cv::Mat imOld=im.clone();
cv::cvtColor(im,im,CV_BGR2RGB);
gtkObj.imshow(&im);
gtkObj.refresh(&imOld);
return 0;
}
Should I redraw image somehow?

Answer 1

FALSE is correct return value. Returning TRUE means "I have dealt with this event" so no further callbacks for particular event ("signal" in GTK+ parlance) are called, in particular default callback is not called so window is not painted. Returning FALSE doesn't stop other callbacks.
I don't think there's much difference. Id' leave it in refresh in order to avoid doing too much work in callbacks.
Quoted warning means that pointer passed to gtk_widget_queue_draw does not contain a GtkWidget. Maybe it hot corrupt? Maybe refresh is called prior to imshow?