GTK+ 事件类型与代码示例解析
1. GDK 事件类型概述
GTK+ 会将以下数据类型传递给事件处理程序，每种数据类型对应的信号也会一并列出。
-GdkEvent：包含拖放结束事件。
-GdkEventType：是一个特殊的数据类型，作为其他数据类型传递给信号处理程序时的指示器，定义为枚举类型，如下所示：
typedef enum { GDK_NOTHING = -1, GDK_DELETE = 0, GDK_DESTROY = 1, GDK_EXPOSE = 2, GDK_MOTION_NOTIFY = 3, GDK_BUTTON_PRESS = 4, GDK_2BUTTON_PRESS = 5, GDK_3BUTTON_PRESS = 6, GDK_BUTTON_RELEASE = 7, GDK_KEY_PRESS = 8, GDK_KEY_RELEASE = 9, GDK_ENTER_NOTIFY = 10, GDK_LEAVE_NOTIFY = 11, GDK_FOCUS_CHANGE = 12, GDK_CONFIGURE = 13, GDK_MAP = 14, GDK_UNMAP = 15, GDK_PROPERTY_NOTIFY = 16, GDK_SELECTION_CLEAR = 17, GDK_SELECTION_REQUEST = 18, GDK_SELEC
