How do I use an image as the background of a gtk toolbar in GTK+2.0

Question

Is there any api like gtk_widget_modify_bg() to modify the background of a gtk toolbar by an image.

gtk_widget_modify_bg() only can change the color of the background.

Answer 1

After one day's try, now I has known how to set an image backgroud for a gtk toolbar.

The keypoint is that you could not directly modify background for GtkToolbar or even GtkVBox (generally you would put GtkToolbar in a GtkVBox). Because they are all none window GtkWidget, so they couldn't catch expose-event, then can't draw their own background. Their background are same as their parent.

But the GtkEventBox can. So you can put the GtkToolbar into a GtkEventBox, and put GtkEventBox into a GtkVBox. Then you modify GtkEventBox's backgroud by an image, It seems GtkToolBar's background changed.

Following is my test codes:

int main(int argc, char* argv[])
{
    GtkWidget* window;
    GtkWidget* vbox;
    GtkWidget* event_box;
    GtkWidget* toolbar;
    GtkToolItem* item;

    gtk_init(&argc, &argv);
    gtk_rc_parse("./gtk.rc");

    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);
    gtk_window_set_default_size(GTK_WINDOW(window), 250, 200);
    gtk_window_set_title(GTK_WINDOW(window), "toolbar");

    vbox = gtk_vbox_new(FALSE, 0);
    gtk_container_add(GTK_CONTAINER(window), vbox);

    event_box = gtk_event_box_new();
    //gtk_widget_set_name(vbox, "toolbar_event_box");
    //set_event_box_background(event_box);
    gtk_box_pack_start(GTK_BOX(vbox), event_box, FALSE, FALSE, 5);

    toolbar = gtk_toolbar_new();
    gtk_toolbar_set_style(GTK_TOOLBAR(toolbar), GTK_TOOLBAR_ICONS);
    gtk_container_set_border_width(GTK_CONTAINER(toolbar), 2);

    item = gtk_tool_button_new_from_stock(GTK_STOCK_NEW);
    gtk_toolbar_insert(GTK_TOOLBAR(toolbar), item, -1);

    item = gtk_tool_button_new_from_stock(GTK_STOCK_OPEN);
    gtk_toolbar_insert(GTK_TOOLBAR(toolbar), item, -1);

    item = gtk_tool_button_new_from_stock(GTK_STOCK_SAVE);
    gtk_toolbar_insert(GTK_TOOLBAR(toolbar), item, -1);

    item = gtk_separator_tool_item_new();
    gtk_toolbar_insert(GTK_TOOLBAR(toolbar), item, -1);

    item = gtk_tool_button_new_from_stock(GTK_STOCK_QUIT);
    g_signal_connect(G_OBJECT(item), "clicked", G_CALLBACK(gtk_main_quit), NULL);
    gtk_toolbar_insert(GTK_TOOLBAR(toolbar), item, -1);

    gtk_container_add(GTK_CONTAINER(event_box), toolbar);

    g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK(gtk_main_quit), NULL);
    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}

and I use gtkrc file to set the GtkEventBox backgroud. Following is the gtk.rc:

pixmap_path "/usr/share/pixmaps:/usr/share/myself"

style "window"
{
  bg_pixmap[NORMAL] = "firefox.png"
}

style "toolbar"
{
  bg_pixmap[NORMAL] = "bk.bmp"
}

widget_class "GtkWindow" style "window"
widget_class "GtkEventBox" style "toolbar"

The result of the program run:

If you don't use gtkrc file, you can use gtk_widget_set_style() to change the GtkEventBox background. like this:

void set_event_box_background(GtkWidget* event_box)
{
    GError* error = NULL;
    GdkPixbuf* pixbuf = gdk_pixbuf_new_from_file("/usr/share/myself/bk.bmp", &error);
    GdkPixmap *pixmap = NULL;
    GdkPixmap *mask = NULL;

    gdk_pixbuf_render_pixmap_and_mask(pixbuf, &pixmap, &mask, 255);
    GtkStyle* orig_style = gtk_widget_get_style(event_box);
    GtkStyle* style = gtk_style_copy(orig_style);
    style->bg_pixmap[GTK_STATE_NORMAL] = pixmap;
    gtk_widget_set_style(event_box, style);
}

I get this method from Yuren's Info Area.
When you use this method, you should comment gtk_rc_parse("./gtk.rc"); and uncomment set_event_box_background(event_box); line at above main() function.