Win32 User Interface API Reference

This section provides documentation for the Windows API functions related to creating and managing the graphical user interface (GUI) for Windows applications.

The Win32 User Interface API encompasses a wide range of functionalities, including window management, message handling, control manipulation, menus, dialog boxes, and more. These APIs are fundamental for developing desktop applications with a rich and interactive user experience.

Key Concepts

• Windows: The basic building blocks of the GUI. Applications create windows to display content and receive user input.
• Messages: A communication mechanism between the operating system and applications, and between different parts of an application.
• Device Context (DC): An information structure that describes drawing attributes, such as the drawing mode, text alignment, background color, and mapping mode.
• GDI (Graphics Device Interface): The subsystem responsible for drawing text and graphics on the screen.

Commonly Used Functions

Function Name	Description
CreateWindowEx	Creates an overlapped, pop-up, or child window.
DefWindowProc	Dispatches a message to the default window procedure.
GetMessage	Retrieves messages from the calling thread's message queue.
TranslateMessage	Translates virtual-key messages into character messages.
DispatchMessage	Dispatches a message to a window procedure.
MessageBox	Displays a message box with specified text and buttons.
DialogBox	Creates a modal dialog box.
InvalidateRect	Adds a rectangle to a window's update region.
UpdateWindow	Updates a window's client area.
SetFocus	Sets the keyboard focus to a specified window.

CreateWindowEx

Creates an overlapped, pop-up, or child window. This is one of the most fundamental functions for creating windows.

HWND CreateWindowEx(
  DWORD     dwExStyle,
  LPCTSTR   lpClassName,
  LPCTSTR   lpWindowName,
  DWORD     dwStyle,
  int       x,
  int       y,
  int       nWidth,
  int       nHeight,
  HWND      hWndParent,
  HMENU     hMenu,
  HINSTANCE hInstance,
  LPVOID    lpParam
);

Parameters:

• dwExStyle: Extended window styles.
• lpClassName: Registered class name.
• lpWindowName: Window text.
• dwStyle: Window styles.
• x, y, nWidth, nHeight: Position and dimensions.
• hWndParent: Handle to the parent window.
• hMenu: Handle to a menu or child-window identifier.
• hInstance: Handle to the application instance.
• lpParam: Application-defined data.

DefWindowProc

Dispatches a message to the default window procedure. This function is typically called by an application's main message loop when it does not handle a particular message.

LRESULT DefWindowProc(
  HWND   hWnd,
  UINT   uMsg,
  WPARAM wParam,
  LPARAM lParam
);

Parameters:

• hWnd: Handle to the window.
• uMsg: The message to be processed.
• wParam: Additional message information.
• lParam: Additional message information.

GetMessage

Retrieves messages from the calling thread's message queue. This is a core part of the message loop.

BOOL GetMessage(
  LPMSG lpMsg,
  HWND  hWnd,
  UINT  wMsgFilterMin,
  UINT  wMsgFilterMax
);

Parameters:

• lpMsg: Pointer to an MSG structure that receives message information.
• hWnd: Handle to the window whose messages are to be retrieved.
• wMsgFilterMin, wMsgFilterMax: Values that restrict the range of messages to be retrieved.

MessageBox

Displays a message box that can contain an application-defined icon, set of buttons, and descriptive text. It's a simple way to communicate with the user.

int MessageBox(
  HWND    hWnd,
  LPCTSTR lpText,
  LPCTSTR lpCaption,
  UINT    uType
);

Parameters:

• hWnd: Handle to the owner window.
• lpText: The message to be displayed.
• lpCaption: The title of the message box.
• uType: The contents and behavior of the message box.

Refer to the full Win32 API documentation for a comprehensive list of functions and their detailed descriptions.