Read windows programming (5)

"Although Windows provides a powerful graphical device interface (GDI) function for graphic display, I will only introduce the display of simple text lines in this chapter. I will also ignore the different font shapes and sizes that Windows can use, and only use the built-in font of windows. This seems to be a limitation. Otherwise, the problems involved and solved in this Chapter apply to all windowsProgramDesign. When text and graphics are mixed, the character size of the font in Windows usually determines the size of the image ."

"In the text mode, the program can output any part of the display, and the content output to the screen will stay in the original place and will not disappear mysteriously. Therefore, the program can discard the information required to regenerate the screen display.

In Windows, you can only draw text and graphics in the display area of the window, in addition, it cannot be ensured that the content displayed in the display area is retained until the program intentionally modifies the content. For example, a user may move another program window on the screen, which may overwrite a portion of your application window. Windows does not save the area covered by other programs in your window. When the program is removed, Windows will require your program to update the display area.

Windows is a message-driven system. It notifies the application of various events by putting messages in the application message queue or sending messages to the appropriate window message processing program. Windows sends the wm_paint Message notification window message handler, and some display areas of the window need to be drawn ."