- WINDOWS MONITOR KEYSTROKES FROM AN INDEPENDENT APPLICATIN DRIVER
- WINDOWS MONITOR KEYSTROKES FROM AN INDEPENDENT APPLICATIN CODE
Assuming a standard keyboard layout, you would get the following sequence of messages: For example, suppose the user presses the SHIFT key followed by the A key. The wParam parameter of the message contains the UTF-16 character.Īs you might guess, WM_CHAR messages are generated from WM_KEYDOWN messages, while WM_SYSCHAR messages are generated from WM_SYSKEYDOWN messages. For each character that is produced, the TranslateMessage function puts a WM_CHAR or WM_SYSCHAR message on the message queue of the window. This function examines key-down messages and translates them into characters. Key strokes are converted into characters by the TranslateMessage function, which we first saw in Module 1. Otherwise, you will block the operating system from handling the command. If you intercept the WM_SYSKEYDOWN message, call DefWindowProc afterward. One flag that might be useful is bit 30, the "previous key state" flag, which is set to 1 for repeated key-down messages.Īs the name implies, system key strokes are primarily intended for use by the operating system. You typically do not need the information in lParam. The lParam parameter contains some miscellaneous information packed into 32 bits.
WINDOWS MONITOR KEYSTROKES FROM AN INDEPENDENT APPLICATIN CODE
In all four of the keyboard messages discussed so far, the wParam parameter contains the virtual-key code of the key. If you hold down a key long enough to start the keyboard's repeat feature, the system sends multiple key-down messages, followed by a single key-up message. When you release a key, the system sends a corresponding key-up message: This includes the function keys other than F10. Some ALT key combinations do not do anything.Īll other key strokes are considered nonsystem keys and produce the WM_KEYDOWN message. In addition, if a window has a menu, the ALT key can be used to activate menu items. For example, ALT + TAB switches to a new window. Various ALT-key combinations invoke system commands. The F10 key activates the menu bar of a window. The WM_SYSKEYDOWN message indicates a system key, which is a key stroke that invokes a system command. When you press a key, the window that has keyboard focus receives one of the following messages. For example, the virtual-key code for the A key is 0x41, but there is no constant named VK_A. No constants are defined for the virtual-key codes that match ASCII values. For the complete list of virtual-key codes, see Virtual-Key Codes. For example, the virtual-key code for the LEFT ARROW key is VK_LEFT (0x25). The header file WinUser.h defines constants for most of the virtual-key codes.
![windows monitor keystrokes from an independent applicatin windows monitor keystrokes from an independent applicatin](https://i.stack.imgur.com/0zGCM.png)
In some respects this mapping is unfortunate, because you should never think of virtual-key codes as characters, for the reasons discussed. A through Z keys = ASCII 'A' – 'Z' (0x41 – 0x5A).That said, the following virtual-key codes do map to ASCII equivalents: This is obvious if you think about it, because the same key can generate different characters (a, A, á), and some keys, such as function keys, do not correspond to any character. In general, virtual-key codes do not correspond to ASCII codes or any other character-encoding standard. Pressing the A key on any keyboard generates the same virtual-key code. Virtual-key codes are device-independent.
WINDOWS MONITOR KEYSTROKES FROM AN INDEPENDENT APPLICATIN DRIVER
The keyboard driver translates scan codes into virtual-key codes. You will almost never care about scan codes. Scan codes vary from one keyboard to the next, and there are separate scan codes for key-up and key-down events. When you press a key, the hardware generates a scan code.