Little problem

[Jpsarapuu]

Hi!

I am trying to make a Hello World program with little more features than usual.
I wanted it to allow running of only one instance of the program. This part was
OK. The problem came when I wanted it to hide/show itself with one key
press. The program hides itself correctly and runs in background but I can't get it back active. Also, I don't want this program to occupy 50% of CPU
Usage. What am I doing wrong?

Here's the code:

#include <windows.h>
#include <ctime>
#include "Resource.h"

HWND MainWindow = 0;


bool InitializeApp(HINSTANCE hInstance, HWND hwnd, int nShowCmd);

int Run();

LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);




int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
	HANDLE hMutex = CreateMutex(NULL, FALSE, "APPLICATION_ID");
	if (GetLastError() == ERROR_ALREADY_EXISTS)
	{
		::MessageBox(0, "Program is already running!", "Error", MB_OK);
		return 0;
	}

	if(!InitializeApp(hInstance, MainWindow, nShowCmd))
	{
		::MessageBox(0, "Initialization Failed!", "Error", MB_OK);
		return 0;
	}

	return Run();
}




bool InitializeApp(HINSTANCE hInstance, HWND hWnd, int nShowCmd)
{
	WNDCLASSEX wc;

	wc.style		 = CS_HREDRAW | CS_VREDRAW;
	wc.lpfnWndProc	 = WndProc;
	wc.cbSize		 = sizeof(WNDCLASSEX);
	wc.cbClsExtra	 = 0;
	wc.cbWndExtra	 = 0;
	wc.hInstance	 = hInstance;
	wc.hIcon		 = ::LoadIcon(hInstance, MAKEINTRESOURCE(WINDOWICON));
	wc.hIconSm		 = ::LoadIcon(hInstance, MAKEINTRESOURCE(WINDOWICON));
	wc.hCursor		 = ::LoadCursor(0, IDC_ARROW);
	wc.hbrBackground = static_cast<HBRUSH>(::GetStockObject(WHITE_BRUSH));
	wc.lpszMenuName  = 0;
	wc.lpszClassName = "HWC"; // Hello World Class

	if(!::RegisterClassEx(&wc))
	{
		::MessageBox(0, "WNDCLASS registration failed!", "Error", 0);
		return false;
	}

	UINT XPOS = (::GetSystemMetrics(SM_CXSCREEN) - WIDTH)  / 2;
	UINT YPOS = (::GetSystemMetrics(SM_CYSCREEN) - HEIGHT) / 2;



    MainWindow = ::CreateWindow(
				   "HWC",
				   "Hello, World!",
				   WS_OVERLAPPEDWINDOW,
				   XPOS,						// Place window in the middle of the screen
				   YPOS,
				   WIDTH,
				   HEIGHT,
				   0,
				   0,
				   hInstance,
				   0);

	if(MainWindow == 0)
	{
		::MessageBox(0, "Window creation failed!", 0, 0);
		return false;
	}

	::ShowWindow(MainWindow, nShowCmd);
	::UpdateWindow(MainWindow);

	return true;
}


int Run()
{
	MSG msg;
	::ZeroMemory(&msg, sizeof(MSG));

	while(TRUE)
	{
		long int startpoint = ::GetTickCount();

		if(::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
		{
			if(msg.message == WM_QUIT)
				break;
			if(msg.message == WM_KEYDOWN)
			{
				if(msg.wParam == VK_DELETE)
				{
					::ShowWindow(MainWindow, SW_HIDE);
					::UpdateWindow(MainWindow);
				}
				if(msg.wParam == VK_SPACE)
				{
					::ShowWindow(MainWindow, SW_SHOW);
					::UpdateWindow(MainWindow);
				}
				if(msg.wParam == VK_ESCAPE)
				{
					::DestroyWindow(MainWindow);
				}
			}
		
			::TranslateMessage(&msg);
			::DispatchMessage(&msg);
		}

		while((::GetTickCount() - startpoint) < 25);
	}

	return msg.wParam;
}



LRESULT CALLBACK WndProc(HWND	hWnd, UINT	msg, WPARAM wParam, LPARAM lParam)
{
	switch(msg)
	{
	case WM_LBUTTONDOWN:
		::MessageBox(0, "Hello, World!", "Hello!", MB_OK);
		return 0;

	case WM_DESTROY:
		::PostQuitMessage(0);
		return 0;
	}
	
	return ::DefWindowProc(hWnd, msg, wParam, lParam);
}

PS. Don't mind the Resource header, it's for the icons that work fine.