C gtk3样式-按钮的背景不变

#include <gtk/gtk.h>

int main(int argc, char *argv[]) {
    gtk_init(&argc, &argv);

    GtkWidget *window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size(GTK_WINDOW(window), 200, 100);

    GtkWidget *button = gtk_button_new_with_label("Button");
    gtk_container_add(GTK_CONTAINER(window), button);

    GtkCssProvider *provider = gtk_css_provider_new();
    gtk_css_provider_load_from_data(provider, "button { background-color: #ff0000; }", -1);
    GtkStyleContext *context = gtk_widget_get_style_context(button);
    gtk_style_context_add_provider(context, GTK_STYLE_PROVIDER(provider), GTK_STYLE_PROVIDER_PRIORITY_USER);

    g_signal_connect(window, "destroy", G_CALLBACK(gtk_main_quit), NULL);

    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}