| With the extensive application of embedded system in the fields of home-electron amusement, a beautiful graphic system with powerful functions is more needed in the embedded system than before. X protocol is mature and provides powerful functions. It has important realistic significance to implement embedded graphic system which supports X protocol.In order to suit variety of low circumstance in the embedded system, the embedded graphic system ClearX realizes a transplantable driver layer. Driver layer is composed of three modules: display driver, mouse driver, keyboard driver. Every module provides a unified and hardware-independent device object for the calls of upper layer. The inner of the device object package the functions of operating hardware, only provides some unified interfaces to communicate with the upper layer.The management of window is an important function of graphic system. The key of it is the clipping of window and the exposure of region. ClearX suggests a method of clipping window using the concept of clipping region. By calculating the clipping region of window, the exposure region of window is divided into two parts: the clipping region and the covered region, then expose them respectively by calling the graphic interfaces of the screen. At last, the operation functions of window are realized, such as show window, hide window, resize window, change the order of windows etc.Event handling module is based on X protocol. After analyzing the relationship between window and event handling, the events which are defined by X protocol will be introduced. Then a input event queue and a client event queue are established, so events are classified into input events and internal system events, a cycle processes them respectively. Finally, aim at three sorts of events: mouse and keyboard event, window cross event, focus change event, a method is suggested to process them with grab mechanism. This module lays a solid foundation for realizing API of X protocol. |
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