问题描述：随便修改一个按钮长度的大小（gtk_table_attach函数里)，都会引起整个界面布局的变化。
                 假定的修改,具体的问题写在代码注释里面，非常希望有人能帮我解答。

#include <gtk/gtk.h>
int main (int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *label;
    GtkWidget *button1;
    GtkWidget *button2;
    GtkWidget *button3;
    GtkWidget *button4;
    GtkWidget *button5;
    GtkWidget *button6;
    GtkWidget *button7;
    GtkWidget *table;
  
    gtk_init (&argc, &argv);
  
    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
    gtk_window_set_title (GTK_WINDOW(window),"计算机学院");
    gtk_widget_set_usize (window, 305, 235);
    gtk_widget_set_uposition(window, 500, 100);
    table = gtk_table_new(2,15,1);
    button1 = gtk_button_new_with_label("记录学生成绩");
    button2 = gtk_button_new_with_label("删除学生成绩");
    button3 = gtk_button_new_with_label("修改学生成绩");
    button4 = gtk_button_new_with_label("查询学生成绩");
    button5 = gtk_button_new_with_label("保存文件");
    button6 = gtk_button_new_with_label("导出文件");
    button7 = gtk_button_new_with_label("退出");
    label = gtk_label_new("成绩管理系统");
  
    gtk_container_add(GTK_CONTAINER(window), table);
    gtk_table_attach (GTK_TABLE(table), button1, 1, 15, 1, 2, (GtkAttachOptions)(GTK_FILL), (GtkAttachOptions)(0), 0, 0);
    gtk_table_attach (GTK_TABLE(table), button2, 1, 15, 2, 3, (GtkAttachOptions)(GTK_FILL), (GtkAttachOptions)(0), 0, 0);
    gtk_table_attach (GTK_TABLE(table), button3, 1, 15, 3, 4, (GtkAttachOptions)(GTK_FILL), (GtkAttachOptions)(0), 0, 0);
    gtk_table_attach (GTK_TABLE(table), button4, 1, 15, 4, 5, (GtkAttachOptions)(GTK_FILL), (GtkAttachOptions)(0), 0, 0);//为什么这里6不能设成15？设成15之后整个界面都变了
    gtk_table_attach (GTK_TABLE(table), button5, 1, 15, 5, 6, (GtkAttachOptions)(GTK_FILL), (GtkAttachOptions)(0), 0, 0);
    gtk_table_attach (GTK_TABLE(table), button6, 1, 15, 6, 7, (GtkAttachOptions)(GTK_FILL), (GtkAttachOptions)(0), 0, 0);
    gtk_table_attach (GTK_TABLE(table), button7, 1, 15, 7, 8, (GtkAttachOptions)(GTK_FILL), (GtkAttachOptions)(0), 0, 0);
    gtk_table_attach (GTK_TABLE(table), label, 0, 16, 0, 1, (GtkAttachOptions)(GTK_FILL), (GtkAttachOptions)(0), 0, 0);  
    //上面这部分，按钮的长度只要发生变化，都会引起整个界面发生变化，为什么阿？我只想改变一个按钮长度而已。
    gtk_widget_show (window);
    gtk_widget_show (table);
    gtk_widget_show (button1);
    gtk_widget_show (button2);
    gtk_widget_show (button3);
    gtk_widget_show (button4);
    gtk_widget_show (button5);
    gtk_widget_show (button6);
    gtk_widget_show (button7);
    gtk_widget_show (label);
  
    gtk_main();
    return 0;
}