我们从preSS键盘上的一个键的那一刻会发生什么，直到它出现在Word文档中 [英] What happens from the moment we press a key on the keyboard, until it appears in your word document

问题描述

这个问题是在我的面试。我只是为了看看我是否给了所有的细节...

This question was in my job interview.. I just to see whether I gave all the details...

推荐答案

• 机械开关短路电阻R1最终拉至地面


• 一个特殊的多路复用器将其转换为一个消息，以减少导线的数量


• 的消息间$ P $由嵌在键盘CPU PTED


• 消息转换为USB协议消息，并调制成零和5伏之间的一系列交流电压的电脉冲的


• USB集线器接收样的措施线路电压周期


• 主机集线器控制器转换消息数据


• 数据进入PC直通USB总线控制器，连接到PCIE总线，直通IRQ notificaitons的组合，DMA传输，由公交车司机发出


• 总线驱动器间$ P $点的消息，并将其转发沿着驱动程序堆栈，最终以一个HID驱动


• HID驱动程序与窗口，最终导致属于MSWORD过程
发送到一个窗口一个窗口消息

• WM_KEYDOWN由DefWindowProc函数转换为WM_CHAR（）。虽然键被按下，多WM_CHARs可以创建。


• Word应用程序捕获WM_CHAR另一个字符添加到文档模型和用户界面的问题，重新渲染


• UI渲染引擎通过加载相应的字体转换UNI code $ C $连接点，以图形图像


• 图形引擎计算整个区域避免闪烁的新形象，并把它逐像素的屏幕

• mechanical switch short-circuits pull up R1 resistor end to the ground
• a special multiplexor translates it into a message, to reduce the number of wires
• the message interpreted by a CPU embedded in the keyboard
• message translated to a USB protocol message, and modulated as a series of electric impulses of alternating voltage between zero and 5 volts
• USB receiving hub measures samples line voltage periodically
• host hub controller translates the message to data
• data enters PC thru USB bus controller, connected to PCIE bus, thru a combination of IRQ notificaitons and a DMA transfer, issued by the bus driver
• Bus driver interprets the message and forwards it along the driver stack, ultimately to an HID driver
• HID driver talks to windows, ultimately resulting in a window message sent to a window belonging to msword process
• WM_KEYDOWN is translated to WM_CHAR by DefWindowProc(). While key is down, multiple WM_CHARs may be created.
• Word application catches WM_CHAR to add another character to the document model and issue re-rendering of UI
• UI rendering engine translates unicode codepoint to graphical image by loading respective font
• graphics engine computes the new image of the whole area to avoid flicker, and puts it pixel-by-pixel to the screen

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