gtk flash images in new thread - c

Question

I use g_thread_new() to create a new thread to implement a flash image effect but only to show the later image but not to flash the 2 images.
And this is the code in the GThreadFunc function:
gdk_threads_enter();
draw_effect(background_map[mbullet.x][mbullet.y +1]);
g_usleep(110000);
draw_background(background_map[mbullet.x][mbullet.y +1]);
gdk_threads_leave();
And this is draw_**()function:
void draw_effect(GtkWidget *widget)
{
gtk_image_set_from_pixbuf(widget,fire_effect);
};
But the program can only show the image that draw_background()draws not draw_effct() does.
Unless I remove the gdk_threads_enter() andgdk_threads_leave() code,can the image flash as I wish.
What's wrong with my code?Can anybody help me?

Answer 1

You're modifying a widget from a thread other than the main thread, which usually leads to all kinds of problems and unexpected behaviors in many GUI libraries, not only gtk.
I do understand the motivation to use a thread here though, since you need to wait a while before redrawing the background.
I recommend that you call draw_effect directly instead of creating a thread, and then use g_timeout_add to schedule a call to a function that will redraw the background.
It should be something like this (please modify as needed and do read the docs):
Define this function:
gboolean
redraw_background (gpointer user_data) {
// ... get references to background_map and mbullet here ...
draw_background(background_map[mbullet.x][mbullet.y +1]);
return FALSE; // so it isn't called again
}
And elsewhere:
// Draw what you need to draw
draw_effect(background_map[mbullet.x][mbullet.y +1]);
// Schedule draw_background 110 ms from now
// user_data will be passed as a parameter to redraw_background
g_timeout_add (110, // milliseconds
redraw_background,
user_data);