The window management functions give applications the means to create and manage a user interface. You use the window management functions to create and use windows to display output, prompt for user input, and carry out the other tasks necessary to support interaction with the user. Most applications create at least one window.
Applications define the general behavior and appearance of their windows by creating window classes and corresponding window procedures. The window class identifies default characteristics, such as whether the window processes double clicks of the mouse buttons or has a menu. The window procedure contains the code that defines the behavior of the window, carries out requested tasks, and processes user input.
Applications generate output for a window using the GDI functions. Because all windows share the display screen, applications do not receive access to the entire screen. Instead, the system manages all output so that it is aligned and clipped to fit within the corresponding window. Applications can draw in a window in response to a request from the system or while processing input messages. When the size or position of a window changes, the system typically sends a message to the application requesting that it paint any previously unexposed area of its window.
Applications receive mouse and keyboard input in the form of messages. The system translates mouse movement, mouse button clicks, and keystrokes into input messages and places these messages in the message queue for the application. The system automatically provides a queue for each application. The application uses message functions to extract messages from the queue and dispatch them to the appropriate window procedure for processing.
Applications can process the mouse and keyboard input directly or let the system translate this low-level input into command messages by using menus and keyboard accelerators. You use menus to present a list of commands to the user. The system manages all the actions required to let the user choose a command and then sends a message identifying the choice to the window procedure. Keyboard accelerators are application-defined combinations of keystrokes that the system translates into messages. Accelerators typically correspond to commands in a menu and generate the same messages.
Applications often respond to command messages by prompting the user for additional information with dialog boxes. A dialog box is a temporary window that displays information or requests input. A dialog box typically includes controls — small, single-purpose windows — that represent buttons and boxes through which the user makes choices or enters information. There are controls for entering text, scrolling text, selecting items from a list of items, and so on. Dialog boxes manage and process the input from these controls, making this information available to the application so that it can complete the requested command.
You can share useful data, such as bitmaps, icons, fonts, and strings, by adding this data as "resources" to the file for an application or DLL. Applications retrieve the data by using the resource functions to locate the resources and load them into memory.
Window management functions provide other features related to windows, such as carets, the clipboard, cursors, hooks, icons, and menus.