C++ Caps Lock Key

Introduction

Caps Lock is a key on the keyboard that, when pressed, capitalizes all letters typed. However, this key is often accidentally pressed, resulting in a lot of capitalized letters that the user did not intend to type. This can be frustrating, especially for programmers who need to write code in a specific format.

C++ has a solution to this problem: the Caps Lock key can be disabled programmatically, so that it does not affect the output. In this guide, we will explore how to disable the Caps Lock key in C++, and how it can be useful for programmers.

Disabling Caps Lock in C++

Using the Windows API

On Windows, the Caps Lock key can be disabled using the SendInput function from the Windows API. Here is a sample code snippet that demonstrates how to disable the Caps Lock key:

// Disable Caps Lock
INPUT input[2];
ZeroMemory(input, sizeof(input));
input[0].type = INPUT_KEYBOARD;
input[0].ki.wVk = VK_CAPITAL;
input[1].type = INPUT_KEYBOARD;
input[1].ki.wVk = VK_CAPITAL;
input[1].ki.dwFlags = KEYEVENTF_KEYUP;
SendInput(2, input, sizeof(INPUT));

This code creates an array of 2 INPUT structures, which are used to simulate keyboard input. The first structure sets the VK_CAPITAL virtual key code to DOWN, while the second structure sets it to UP. This effectively cancels out the Caps Lock key press, so that it does not affect the output.

Using the X11 API

On Linux, the Caps Lock key can be disabled using the X11 API. Here is a sample code snippet that demonstrates how to disable the Caps Lock key using X11:

// Disable Caps Lock
Display* display = XOpenDisplay(NULL);
XModifierKeymap* modMap = XGetModifierMapping(display);
KeyCode kc = XKeysymToKeycode(display, XK_Caps_Lock);
int max = modMap->max_keypermod * 8;
for (int i = 0; i < max; i++) {
    if (modMap->modifiermap[i] == kc) {
        modMap->modifiermap[i] = 0;
    }
}
XSetModifierMapping(display, modMap);
XCloseDisplay(display);

This code uses the X11 API to obtain the modifier key map, and then searches for the Caps Lock key (XK_Caps_Lock) in the map. Once the key is found, it is set to 0 in the map, effectively disabling the Caps Lock key.

Conclusion

Disabling the Caps Lock key in C++ can be a useful tool for programmers who want to avoid accidental capitalization in their code. With the Windows API and the X11 API, it is possible to programmatically disable the Caps Lock key in C++.