Input API

This section provides details on the Windows API functions and structures used for handling user input, including keyboard, mouse, touch, and pen input.

Core Input Concepts

Understanding the fundamental concepts of input in Windows is crucial for developing responsive and intuitive applications. This includes:

• Input Messages: How Windows systems generate and dispatch input events as messages.
• Input Devices: The different types of input devices supported by Windows and their characteristics.
• Input Event Handling: Techniques for capturing, processing, and responding to input events.
• Input Focus: How applications manage which window or control receives input.

Keyboard Input

The keyboard is a primary input device. The following APIs are essential for keyboard input:

• GetMessage / PeekMessage: Retrieving keyboard messages.
• TranslateMessage: Translating virtual-key messages into character messages.
• DispatchMessage: Sending messages to the appropriate window procedure.
• Virtual-Key Codes: Constants representing specific keys (e.g., VK_SHIFT, VK_RETURN).
• GetAsyncKeyState / GetKeyState: Checking the current state of a key.

For more advanced keyboard handling, consider:

• DirectInput: A lower-level API for more direct device access, often used in games.

Mouse Input

Mouse input is handled through specific messages and functions:

• Mouse Messages: Such as WM_LBUTTONDOWN, WM_MOUSEMOVE, WM_RBUTTONUP.
• Cursor Handling: Setting and managing the mouse cursor's appearance and position.
• Coordinate Systems: Understanding screen coordinates versus client coordinates.

Touch and Pen Input

Modern Windows applications leverage touch and pen input:

• Pointer Input: A unified API for handling input from various pointing devices, including touch, pen, and mouse.
• WM_POINTERUPDATE, WM_POINTERDOWN, WM_POINTERUP: Messages for pointer input.
• Pointer Types: Differentiating between touch, pen, and mouse pointers.
• Stylus Input: Specific handling for pen-based input, including pressure and tilt.

Input Structures

Several structures are used to convey input data:

Structure	Description
MSG	Contains message information retrieved from the message queue.
KBDLLHOOKSTRUCT	Information about a low-level keyboard input event.
MSLLHOOKSTRUCT	Information about a low-level mouse input event.
POINTER_INFO	Contains information about a pointer.
TOUCH_INFO	Contains information about a touch input contact.