GSettings值似乎发生了变化，但并未持续存在

Question

GSettings值似乎在我的C代码中有所改变，但它不会持续存在。 dconf-editor显示它保持不变（默认的“picture-uri”设置）。

我错过了什么吗？

#include <stdio.h>
#include <gio/gio.h>

int main() {
    GSettings * background_settings = g_settings_new("org.gnome.desktop.background");

    printf("\"picture-uri\" setting is writable? \n%d\n\n", g_settings_is_writable(background_settings, "picture_uri"));

    GVariant * picture_uri_setting = g_settings_get_value(background_settings, "picture-uri");
    char * picture_uri_setting_value;
    g_variant_get(picture_uri_setting, "&s", &picture_uri_setting_value);
    printf("Before: %s\n", picture_uri_setting_value);

    GVariant * new_picture_uri_setting = g_variant_new("&s", "file:///tmp/wall.jpg");
    g_settings_set_value(background_settings, "picture-uri", new_picture_uri_setting);

    picture_uri_setting = g_settings_get_value(background_settings, "picture-uri");
    g_variant_get(picture_uri_setting, "&s", &picture_uri_setting_value);
    printf("After: %s\n", picture_uri_setting_value);

    return 0;
}

这是我编译它的方式：

gcc -Wall -g --save-temps main.c $(pkg-config --libs --cflags gtk+-3.0)

感谢。