How to build the value of WM_CHAR vkCode for non alpha characters?

Question

How to build the vkCode value of WM_CHAR lParam for non-alpha characters !@#$%¨&*()-= etc?

test("a#b@c&d*ef-g+!h", hWnd); struct extraKeyInfo { unsigned short repeatCount = 1; unsigned char scanCode; bool extendedKey = 0; bool contextCode = 0; bool prevKeyState = 0; bool transitionState = 0; operator unsigned int() { return repeatCount | (scanCode << 16) | (extendedKey << 24) | (contextCode << 29) | (prevKeyState << 30) | (transitionState << 31); } }; void test(const char* str, HWND hWnd) { extraKeyInfo lParam = {}; for (int i = 0; i < strlen(str); i++) { short vkCode = LOBYTE(VkKeyScan(str[i])); // vkCode 32 = space. if ((!isalpha(str[i])) && (vkCode != 32)) vkCode << 19; /* <= my doubt lies here */ lParam.scanCode = MapVirtualKey(vkCode, MAPVK_VK_TO_VSC); PostMessage(hWnd, WM_CHAR, vkCode, lParam); } return; }

Are you sure that your target app will accept input like this? — David Heffernan
– David Heffernan, Commented Aug 20, 2022 at 7:49
@DavidHeffernan There's something wrong? I'm testing and it's accepting normally, I am in doubt about how to construct the lParam for non-alpha char. — Cesar
– Cesar, Commented Aug 20, 2022 at 8:09
Yes, vkCode << 19; is definitely a problem (or two). 1. vkCode is a short, which contains 16 bits, and it is shifted 19 positions. That is not going to work well. And 2. The result isn't stored anywhere. — BoP
– BoP, Commented Aug 20, 2022 at 8:38
Well, only a minority of apps will respond to faking input this way. The correct way is with SendInput. But more generally UIAutomation is how to automate other processes. — David Heffernan
– David Heffernan, Commented Aug 20, 2022 at 9:30
I suggest you could try to use MapVirtualKeyA function.You could refer to the thread: stackoverflow.com/questions/7682999/… — Jeaninez - MSFT
– Jeaninez - MSFT, Commented Aug 22, 2022 at 9:02

jwezorek · Accepted Answer · 2022-08-20 16:55:50Z

You can use the Win32 API call VkKeyScanEx to convert a character value to a virtual key code. Note however that virtual key codes identify keys so they depend on keyboard layout and there is not a one-to-one correspondence between printable characters and key codes because multiple characters may be associated with the same key but distinguished via shift state.

#include <Windows.h> #include <iostream> short get_virtual_key_code(char ch) { auto key_code = VkKeyScanExA(ch, 0); return LOBYTE(key_code); // high byte contains modifier flags e.g. shift etc. } int main() { std::cout << "A => " << std::hex << get_virtual_key_code('A') << "\n"; // 0x41 std::cout << "a => " << std::hex << get_virtual_key_code('a') << "\n"; // 0x41 again, same key code different flags std::cout << "/ => " << std::hex << get_virtual_key_code('/') << "\n"; // typically 0xBF on US keyboards. return 0; }

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How to build the value of WM_CHAR vkCode for non alpha characters?

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