List control panel applets and allow the user to open them

list-cpls.cpp

/*
List and load Control Panel applets

Based on this article:
https://blogs.msdn.microsoft.com/oldnewthing/archive/2003/12/26/45979.aspx

And this section of MSDN:
https://msdn.microsoft.com/en-us/library/windows/desktop/cc144185(v=vs.85).aspx

KNOWN BUGS:
- should call STOP once per applet at end and EXIT once for the applet library
*/

#define STRICT
#include <windows.h>
#include <windowsx.h>
#include <ole2.h>
#include <commctrl.h>
#include <shlwapi.h>
#include <cpl.h>

#include <string>
#include <vector>
#include <stdio.h>

#define IDC_LISTBOX 101

typedef std::basic_string<TCHAR> tstring;

struct ControlPanelApplet
{
	tstring name;
	int index;
	// tstring filepath;

	APPLET_PROC pfnCPlApplet;
	CPLINFO cpli;

	ACTCTX act;
	HANDLE hctx;
	ULONG_PTR ulCookie;
	HINSTANCE hinstCPL;
};

class MyApplication
{
// ----------------------------------------------
// Public Methods
// ----------------------------------------------
public:
	static const int padding = 20;

	MyApplication(HINSTANCE);
	~MyApplication();

	// handle window message
	LRESULT handleMessage(UINT uiMsg, WPARAM wParam, LPARAM lParam);

	// run the main message loop
	void run(int nShowCmd);

// ----------------------------------------------
// Private Methods
// ----------------------------------------------
private:
	void registerClass();
	void fatalError(LPCTSTR msg);
	
	void createListBox();
	void addListBoxItem(LPCTSTR item);

	void loadApplets();
	void loadApplet(LPCTSTR appletName);
	void unloadApplets();

	LPCTSTR className() { return TEXT("NiaApplicationWindow"); }

	// Window event methods
	void onResize(long request, int width, int height);
	void onKeyUp(unsigned long keyCode);
	void onCommand(long notification, long identifier, HWND control);

// ----------------------------------------------
// Instance Variables
// ----------------------------------------------
private:
	std::vector<ControlPanelApplet> applets;
	bool cleared;

	HINSTANCE hinst;
	HWND topWindow, listBox;
	HFONT defaultFont;

};


// ----------------------------------------------
// Window Procedure
// ----------------------------------------------
LRESULT CALLBACK
WndProc(HWND hwnd, UINT uiMsg, WPARAM wParam, LPARAM lParam)
{
	if (uiMsg == WM_CREATE)
	{
		CREATESTRUCT *lpCreateStruct = reinterpret_cast<CREATESTRUCT*>(lParam);
		SetWindowLongPtr(hwnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(lpCreateStruct->lpCreateParams));
	}
	else
	{
		MyApplication *self = reinterpret_cast<MyApplication*>(GetWindowLongPtr(hwnd, GWLP_USERDATA));

		if (self != NULL)
		{
			return self->handleMessage(uiMsg, wParam, lParam);
		}
		else
		{
			return DefWindowProc(hwnd, uiMsg, wParam, lParam);
		}
	}
}

// ----------------------------------------------
// Application Entry Point
// ----------------------------------------------
int WINAPI WinMain(HINSTANCE hinst, HINSTANCE hinstPrev, LPSTR lpCmdLine, int nShowCmd)
{
	MyApplication app(hinst);
	app.run(nShowCmd);
}

void MyApplication::fatalError(LPCTSTR msg)
{
	MessageBox(topWindow, msg, TEXT("Fatal Error"), MB_OK|MB_ICONEXCLAMATION);
	DestroyWindow(topWindow);
}

MyApplication::MyApplication(HINSTANCE hinst) : hinst(hinst), cleared(false)
{
	registerClass();

	INITCOMMONCONTROLSEX icc;
	icc.dwSize = sizeof(INITCOMMONCONTROLSEX);
	icc.dwICC = ICC_STANDARD_CLASSES;
	InitCommonControlsEx(&icc);

	NONCLIENTMETRICS metrics;
	metrics.cbSize = sizeof(NONCLIENTMETRICS);
	SystemParametersInfo(SPI_GETNONCLIENTMETRICS, sizeof(NONCLIENTMETRICS), &metrics, 0);
	defaultFont = ::CreateFontIndirect(&metrics.lfMessageFont);

	topWindow = CreateWindow(
		className(), TEXT("My Control Panel"), WS_OVERLAPPEDWINDOW,
		// WS_POPUPWINDOW | WS_CAPTION ,
		100, 100, 800, 600,
		NULL, NULL, hinst, this
	);

	createListBox();
}

MyApplication::~MyApplication()
{
	DeleteObject(defaultFont);
	unloadApplets();
}

void MyApplication::unloadApplets()
{
	printf("unloading applets\n");
	for (std::vector<ControlPanelApplet>::iterator it = applets.begin();
		it != applets.end();
		++it)
	{
		it->pfnCPlApplet(topWindow, CPL_STOP, 0, it->cpli.lData);
		it->pfnCPlApplet(topWindow, CPL_EXIT, 0, 0);
		FreeLibrary(it->hinstCPL);
	}
}

void MyApplication::registerClass()
{
	WNDCLASS wc;

	wc.style = 0;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hinst;
    wc.hIcon = NULL;
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = className();

    RegisterClass(&wc);
}

void MyApplication::createListBox()
{
	RECT r;
	GetClientRect(topWindow, &r);

	listBox = CreateWindow(
		WC_LISTBOX, NULL, WS_CHILD | WS_VISIBLE | LBS_NOTIFY,
		padding, padding, r.right - padding, r.bottom - padding,
		topWindow, (HMENU) IDC_LISTBOX, hinst, NULL
	);

	SendMessage(listBox, WM_SETFONT, reinterpret_cast<WPARAM>(defaultFont), MAKELPARAM(TRUE, 0));

	loadApplets();
}

void MyApplication::addListBoxItem(LPCTSTR item)
{
	SendMessage(listBox, LB_ADDSTRING, 0, reinterpret_cast<LPARAM>(item));
}

void MyApplication::loadApplets()
{
	LONG ret;
	HKEY cpls;
	DWORD amountKeys, maxKeySize;

	ret = RegOpenKeyEx(
		HKEY_LOCAL_MACHINE, 
		TEXT("Software\\Microsoft\\Windows\\CurrentVersion\\Control Panel\\Cpls"),
		0, KEY_READ, &cpls
	);
	if (ret != ERROR_SUCCESS)
	{
		fatalError(TEXT("Could not load Cpls registry key"));
	}

	ret = RegQueryInfoKey(cpls, NULL, NULL, NULL, &amountKeys, &maxKeySize, NULL, NULL, NULL, NULL, NULL, NULL);
	if (ret != ERROR_SUCCESS)
	{
		fatalError(TEXT("Could not query Cpls registry key"));
	}

	if (amountKeys)
	{
		DWORD keyBufsize = maxKeySize+1;
		// printf("%d subkeys - max subkey length: %d\n", amountKeys, keyBufsize);
		TCHAR keyBuff[keyBufsize];

		for (int i = 0; i < amountKeys; i++)
		{
			keyBufsize = maxKeySize+1;
			ret = RegEnumKeyEx(cpls, i, keyBuff, &keyBufsize, NULL, NULL, NULL, NULL);

			if (ret == ERROR_SUCCESS)
			{
				// addListBoxItem(keyBuff);
				loadApplet(keyBuff);
			}
			else
			{
				printf("error detected for subkey %d (error code: %d)\n", i, ret);
			}
		}
	}

	RegCloseKey(cpls);
}

void MyApplication::loadApplet(LPCTSTR appletName)
{
	TCHAR szPath[MAX_PATH];
	LPTSTR pszLast;
	DWORD cch = SearchPath(NULL, appletName,
                         NULL, MAX_PATH, szPath, &pszLast);

	if (cch < 0 && cch > MAX_PATH) {
		return;
	}

	ControlPanelApplet applet;
	// applet.filepath = szPath;
	// applet.act = { 0 };
	applet.act.cbSize = sizeof(applet.act);
	applet.act.dwFlags = 0;
	applet.act.lpSource = szPath;
	applet.act.lpResourceName = MAKEINTRESOURCE(123);
	applet.hctx = CreateActCtx(&applet.act);

	if (applet.hctx == INVALID_HANDLE_VALUE || ActivateActCtx(applet.hctx, &applet.ulCookie))
	{
		applet.hinstCPL = LoadLibrary(szPath);
		if (applet.hinstCPL)
		{
			applet.pfnCPlApplet = (APPLET_PROC) GetProcAddress(applet.hinstCPL, "CPlApplet");
			if (applet.pfnCPlApplet)
			{
				int cApplets = applet.pfnCPlApplet(topWindow, CPL_GETCOUNT, 0, 0);
          		// printf("%d applet(s) detected\n", cApplets);

          		if (cApplets)
          		{
          			for (int i = 0; i < cApplets; i++)
          			{
            			TCHAR szAppletName[256];

            			applet.pfnCPlApplet(topWindow, CPL_INQUIRE, 0, (LPARAM)&applet.cpli);
            			LoadString(applet.hinstCPL, applet.cpli.idName, szAppletName, 256);
            			applet.index = i;
            			applet.name = szAppletName;

            			applets.push_back(applet);
            			addListBoxItem(applet.name.c_str());
          			}
          		}
			}
			else
			{
				FreeLibrary(applet.hinstCPL);
			}
		}
	}
}

void MyApplication::run(int nShowCmd)
{
	ShowWindow(topWindow, nShowCmd);

	MSG msg;
	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
}

LRESULT MyApplication::handleMessage(UINT uiMsg, WPARAM wParam, LPARAM lParam)
{
	switch(uiMsg)
	{
		case WM_SIZE: {
			onResize(wParam, LOWORD(lParam), HIWORD(lParam));
			return 0;
		}

		/*
		case WM_CLOSE: {
			// unloadApplets();
			return DefWindowProc(topWindow, uiMsg, wParam, lParam);
		}
		*/

		case WM_DESTROY: {
			PostQuitMessage(0);
			return 0;
		}

		case WM_KEYUP: {
			onKeyUp(wParam);
			return 0;
		}

		case WM_COMMAND: {
			onCommand(HIWORD(wParam), LOWORD(wParam), reinterpret_cast<HWND>(lParam));
			return 0;
		}

		default: {
			return DefWindowProc(topWindow, uiMsg, wParam, lParam);
		}
	}
}

void MyApplication::onResize(long request, int width, int height)
{
	RECT rc;
	GetClientRect(topWindow, &rc);
	// printf("width: %d, height: %d -- width: %d, height: %d\n", rc.right, rc.bottom, rc.right - padding, rc.bottom - padding);
	SetWindowPos(listBox, NULL, 0, 0, rc.right - (padding*2), rc.bottom - (padding*2), SWP_NOMOVE | SWP_NOOWNERZORDER);
	// SetWindowPos(listBox, NULL, 0, 0, 200, 200, SWP_NOMOVE | SWP_NOOWNERZORDER);
}

void MyApplication::onKeyUp(unsigned long keyCode)
{
	if (keyCode == VK_ESCAPE)
	{
		DestroyWindow(topWindow);
	}
}

void MyApplication::onCommand(long notification, long identifier, HWND control)
{
	if (identifier == IDC_LISTBOX && notification == LBN_DBLCLK)
	{
		long selectedItem = SendMessage(listBox, LB_GETCURSEL, 0, 0);
		if (selectedItem < applets.size())
		{
			ControlPanelApplet& applet = applets[selectedItem];
			applet.pfnCPlApplet(topWindow, CPL_DBLCLK, 0, applet.cpli.lData);
		}
	}
}