discord-rpc/src/discord-register.cpp

#include "discord-rpc.h"
#include <stdio.h>

#ifdef _WIN32
#define WIN32_LEAN_AND_MEAN
#define NOMCX
#define NOSERVICE
#define NOIME
#include <windows.h>
#include <Psapi.h>
#include <Strsafe.h>
#pragma comment(lib, "Psapi.lib")
#endif

void Discord_Register(const char* applicationId)
{
#ifdef _WIN32
    // https://msdn.microsoft.com/en-us/library/aa767914(v=vs.85).aspx
    // we want to register games so we can run them as discord-<appid>://
    // Update the HKEY_CURRENT_USER, because it doesn't seem to require special permissions.

    wchar_t appId[32];
    MultiByteToWideChar(CP_UTF8, 0, applicationId, -1, appId, 32);

    wchar_t exeFilePath[MAX_PATH];
    GetModuleFileNameExW(GetCurrentProcess(), nullptr, exeFilePath, MAX_PATH);

    wchar_t protocolName[64];
    StringCbPrintfW(protocolName, sizeof(protocolName), L"discord-%s", appId);
    wchar_t protocolDescription[128];
    StringCbPrintfW(
      protocolDescription, sizeof(protocolDescription), L"URL:Run game %s protocol", appId);
    wchar_t urlProtocol = 0;
    wchar_t openCommand[MAX_PATH + 8];
    StringCbPrintfW(openCommand, sizeof(openCommand), L"\"%s\" \"%%1\"", exeFilePath);

    wchar_t keyName[256];
    StringCbPrintfW(keyName, sizeof(keyName), L"Software\\Classes\\%s", protocolName);
    HKEY key;
    auto status =
      RegCreateKeyExW(HKEY_CURRENT_USER, keyName, 0, nullptr, 0, KEY_WRITE, nullptr, &key, nullptr);
    if (status != ERROR_SUCCESS) {
        fprintf(stderr, "Error creating key\n");
        return;
    }
    DWORD len;
    LSTATUS result;
    len = lstrlenW(protocolDescription) + 1;
    result =
      RegSetKeyValueW(key, nullptr, nullptr, REG_SZ, protocolDescription, len * sizeof(wchar_t));
    if (FAILED(result)) {
        fprintf(stderr, "Error writing description\n");
    }

    len = lstrlenW(protocolDescription) + 1;
    result = RegSetKeyValueW(key, nullptr, L"URL Protocol", REG_SZ, &urlProtocol, sizeof(wchar_t));
    if (FAILED(result)) {
        fprintf(stderr, "Error writing description\n");
    }

    len = lstrlenW(exeFilePath) + 1;
    result =
      RegSetKeyValueW(key, L"DefaultIcon", nullptr, REG_SZ, exeFilePath, len * sizeof(wchar_t));
    if (FAILED(result)) {
        fprintf(stderr, "Error writing icon\n");
    }

    len = lstrlenW(openCommand) + 1;
    result = RegSetKeyValueW(
      key, L"shell\\open\\command", nullptr, REG_SZ, openCommand, len * sizeof(wchar_t));
    if (FAILED(result)) {
        fprintf(stderr, "Error writing command\n");
    }
    RegCloseKey(key);
#endif
}