Animated eyes following mouse movement

mouseeye.cpp

#define WIN32_LEAN_AND_MEAN
#define _USE_MATH_DEFINES
#include <windows.h>
#include <stdio.h>
#include <math.h>

POINT CalcEyePosition(HWND hWnd, RECT *rcClient)
{
	POINT ptWindow;
	ptWindow.x = rcClient->right / 2;
	ptWindow.y = rcClient->bottom / 2;
	ClientToScreen(hWnd, &ptWindow);

	POINT ptCursor;
	GetCursorPos(&ptCursor);

	double deg = (double)(ptCursor.x - ptWindow.x);
	deg /= (double)(ptCursor.y - ptWindow.y);
	deg = atan(deg);

	int a = rcClient->right / 4;
	int b = rcClient->bottom / 2;

	POINT pt;
	if (ptCursor.y > ptWindow.y)
	{
		pt.x = (LONG)(a/2 * sin(deg) + a); 
		pt.y = (LONG)(b/2 * cos(deg) + b);
	}
	else
	{
		pt.x = (LONG)(a - (a/2 * sin(deg)));
		pt.y = (LONG)(b - (b/2 * cos(deg)));
	}

	return pt;
}

void UpdateFrame(HWND hWnd)
{
	RECT rcClient;
	GetClientRect(hWnd, &rcClient);

	HDC hDC = GetDC(hWnd);
	if (hDC)
	{
		Ellipse(hDC, 0, 0, (rcClient.right / 2) - 2, rcClient.bottom-1);
		Ellipse(hDC, (rcClient.right / 2) + 1, 0, rcClient.right - 2, rcClient.bottom-1);

		int wx = rcClient.right / 16, wy = rcClient.bottom / 8;
		int mx = rcClient.right / 2,  my = rcClient.bottom / 2;

		SelectObject(hDC, GetStockObject(BLACK_BRUSH));
		POINT pt = CalcEyePosition(hWnd, &rcClient);
		Ellipse(hDC, pt.x -wx , pt.y - wy, pt.x + wx, pt.y + wy);
		Ellipse(hDC, pt.x + mx - wx, pt.y - wy, pt.x + mx + wx, pt.y + wy);
		
		ReleaseDC(hWnd, hDC);
	}
}

void ResetRegion(HWND hWnd, WORD width, WORD height)
{
	HRGN l_eye = CreateEllipticRgn(0, 0, (width / 2) - 1, height);
	HRGN r_eye = CreateEllipticRgn((width / 2) + 1, 0, width - 1, height);
	CombineRgn(l_eye, l_eye, r_eye, RGN_OR);
	SetWindowRgn(hWnd, l_eye, TRUE); 
}

void SaveSettings(HWND hWnd)
{
	char name[MAX_PATH];
	GetModuleFileName(NULL, name, sizeof(name));
	size_t pos = strlen(name); 
	name[pos - 3] = 'i';
	name[pos - 2] = 'n';
	name[pos - 1] = 'i';
	RECT rc;           GetClientRect(hWnd, &rc);
	POINT pt = {0, 0}; ClientToScreen(hWnd, &pt);
	char tmp[32];
	sprintf(tmp, "%d", pt.x);      WritePrivateProfileString("Settings", "PosX",   tmp, name);
	sprintf(tmp, "%d", pt.y);      WritePrivateProfileString("Settings", "PosY",   tmp, name);
	sprintf(tmp, "%d", rc.right);  WritePrivateProfileString("Settings", "Width",  tmp, name);
	sprintf(tmp, "%d", rc.bottom); WritePrivateProfileString("Settings", "Height", tmp, name);
}

RECT ReadSettings()
{
	RECT rc;
	char name[MAX_PATH];
	GetModuleFileName(NULL, name, sizeof(name));
	size_t pos = strlen(name);
	name[pos - 3] = 'i';
	name[pos - 2] = 'n';
	name[pos - 1] = 'i';
	rc.left   = GetPrivateProfileInt("Settings", "PosX",   100, name);
	rc.top    = GetPrivateProfileInt("Settings", "PosY",   100, name);
	rc.right  = GetPrivateProfileInt("Settings", "Width",  200, name);
	rc.bottom = GetPrivateProfileInt("Settings", "Height", 125, name);
	return rc;
}

LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
	switch (uMsg)
	{
	case WM_PAINT:
		{
			PAINTSTRUCT ps;
			BeginPaint(hWnd, &ps);
			UpdateFrame(hWnd);
			EndPaint(hWnd, &ps);
		}
		break;
	case WM_TIMER:
		UpdateFrame(hWnd);
		break;
	case WM_SIZE:
		ResetRegion(hWnd, LOWORD(lParam), HIWORD(lParam));
		break;
	case WM_LBUTTONDBLCLK:
		{
			if (MessageBox(hWnd, "Wirklich beenden?", "MouseEyes", MB_YESNO | MB_ICONQUESTION) == IDYES)
				PostMessage(hWnd, WM_CLOSE, 0, 0);
		}
		break;
	case WM_NCHITTEST:
		{
			POINT pt; RECT rc;
			pt.x = LOWORD(lParam);
			pt.y = HIWORD(lParam);
			ScreenToClient(hWnd, &pt);		
			GetClientRect(hWnd, &rc);
			if (pt.x > 0.75 * rc.right && pt.y > rc.bottom / 2)
				return HTBOTTOMRIGHT;
			else if (pt.x > rc.right / 2)
					return HTCAPTION;
			else return HTCLIENT;
		}
	case WM_CLOSE:
		{
			SaveSettings(hWnd);
			PostQuitMessage(0);
			return 0L;
		}
	}
	return DefWindowProc(hWnd, uMsg, wParam, lParam);
}

int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrevInst, LPSTR lpCmdLine, int nCmdShow)
{
	if (FindWindow("MouseEye", NULL)) return 0;

	WNDCLASS wc;
	wc.hInstance     = hInst;
	wc.cbClsExtra    = 0;
	wc.cbWndExtra    = 0;
	wc.hbrBackground = reinterpret_cast<HBRUSH>(GetStockObject(WHITE_BRUSH));
	wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
	wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
	wc.lpfnWndProc   = WindowProc;
	wc.lpszClassName = "MouseEye";
	wc.lpszMenuName  = NULL;
	wc.style         = CS_HREDRAW | CS_VREDRAW | CS_DBLCLKS;

	RegisterClass(&wc);
	//HWND hWnd = CreateWindow("MouseEye", "MouseEye", WS_CAPTION|WS_SYSMENU|WS_MINIMIZEBOX|WS_THICKFRAME, 100, 100, 200, 125, NULL, NULL, hInst, NULL);
	HWND hWnd = CreateWindow("MouseEye", "MouseEye", WS_POPUP, 100, 100, 200, 125, NULL, NULL, hInst, NULL);

	if (!hWnd) 
	{
		MessageBox(NULL, "Cannot Create Window!", "Error", MB_ICONERROR | MB_OK);
		return 1;
	}

	RECT wndSettings = ReadSettings();

	SetWindowPos(hWnd, HWND_TOPMOST, wndSettings.left, wndSettings.top, wndSettings.right, wndSettings.bottom, 0);
	ShowWindow(hWnd, nCmdShow);
	UpdateWindow(hWnd);

	RECT rcClient;
	GetClientRect(hWnd, &rcClient);
	ResetRegion(hWnd, (WORD)rcClient.right, (WORD) rcClient.bottom);

	SetTimer(hWnd, 1, 100, NULL);

	MSG msg;
	while (GetMessage(&msg, NULL, 0, 0))
	{
		TranslateMessage(&msg);
		DispatchMessage(&msg);
	}
	return (int) msg.wParam;	
}