바깥 테두리 투명 처리

SetWindowRgn 란 함수로 처리한단다..

간단하게 예제로 보면

 //원형 시계

//ExClock.c
#include <windows.h>
#include <stdlib.h>
#include <time.h>

#define CLOCKTIMER 1
#define CLOCKSIZE 100

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
VOID CALLBACK TimeProc(HWND hwnd,UINT iMsg,UINT wParam,DWORD lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
				   PSTR szCmdLine, int iCmdShow)
{
	static char szAppName[] = "ExClock";
	HWND        hwnd;
	MSG         msg;
	WNDCLASSEX  wndclass;
	int cx,x;

	wndclass.cbSize        = sizeof(wndclass);
	wndclass.style         = CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc   = WndProc;
	wndclass.cbClsExtra    = 0;
	wndclass.cbWndExtra    = 0;
	wndclass.hInstance     = hInstance;
	wndclass.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hCursor       = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wndclass.lpszMenuName  = NULL;
	wndclass.lpszClassName = szAppName;
	wndclass.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);

	RegisterClassEx(&wndclass);
	//스크린의 가로 크기를 얻는다.
	cx=GetSystemMetrics(SM_CXFULLSCREEN);
	x=cx-CLOCKSIZE;

	hwnd = CreateWindow(szAppName,
						"원형시계 예제:ExClock",
						WS_POPUP | WS_VISIBLE,
						x,
						0,
						CLOCKSIZE,
						CLOCKSIZE,
						NULL,
						NULL,
						hInstance,
						NULL);

	ShowWindow(hwnd, iCmdShow);
	UpdateWindow(hwnd);

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

LRESULT CALLBACK WndProc(HWND hwnd, UINT iMsg, WPARAM wParam, LPARAM lParam)
{
	HDC         hdc;
	PAINTSTRUCT ps;
	HBRUSH hBrush,oldBrush;
	HPEN   hPen,oldPen;
	HRGN rgn;
	switch(iMsg)
	{
	case WM_CREATE:
		SetTimer(hwnd,CLOCKTIMER,100,(TIMERPROC)TimeProc);
		rgn=CreateRoundRectRgn(0,0,CLOCKSIZE,CLOCKSIZE,CLOCKSIZE,CLOCKSIZE);
		SetWindowRgn(hwnd,rgn,FALSE);
		return 0;
	case WM_PAINT:
		hdc = BeginPaint(hwnd, &ps);
		hBrush=CreateSolidBrush(RGB(0,0,200));
		hPen=CreatePen(PS_SOLID,3,RGB(200,200,91));
		oldBrush=SelectObject(hdc,hBrush);
		oldPen=SelectObject(hdc,hPen);

		RoundRect(hdc,0,0,CLOCKSIZE,CLOCKSIZE,CLOCKSIZE,CLOCKSIZE);

		SelectObject(hdc,CreateSolidBrush(RGB(0,0,0)));
		RoundRect(hdc,15,30,85,60,20,20);
		SelectObject(hdc,oldBrush);
		SelectObject(hdc,oldPen);
		DeleteObject(hBrush);
		DeleteObject(hPen);
		EndPaint (hwnd, &ps) ;
		return 0;
	case WM_DESTROY:
		KillTimer(hwnd,CLOCKTIMER);
		PostQuitMessage(0);
		return 0;
	}
	return DefWindowProc(hwnd, iMsg, wParam, lParam);
}

VOID CALLBACK TimeProc(HWND hwnd,UINT iMsg,UINT wParam,DWORD lParam)
{
	time_t curtime;
	struct tm cur;
	char curdate[80];
	HDC hdc;
	time(&curtime);
	cur=*localtime(&curtime);
	wsprintf(curdate,"%02d:%02d:%02d",cur.tm_hour,cur.tm_min,cur.tm_sec);
	hdc=GetDC(hwnd);
	SetBkColor(hdc,RGB(0,0,0));
	SetTextColor(hdc,RGB(255,255,0));
	TextOut(hdc,20,37,curdate,strlen(curdate));
	ReleaseDC(hwnd,hdc);
}