im trying to get my window to update using update UpdateLayeredWindow, but no luck so far.

void update(HWND hwnd){
	HDC pDC = GetDC(hwnd);
	HDC dcMem;
	dcMem = CreateCompatibleDC(pDC);
 
	HBITMAP bmp;
	//bmp = LoadBitmap(aInstance, "clockbg.bmp");
	bmp = LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_BITMAP1));
	if(!bmp)MessageBox(NULL,"FAIL TO LOAD IMAGE", "ERROR",NULL);
 
	HBITMAP pOldBitmap = (HBITMAP) SelectObject(dcMem, bmp);
 
 
	BLENDFUNCTION blend;
	blend.BlendOp = AC_SRC_OVER;
	blend.BlendFlags = 0;
	blend.SourceConstantAlpha = 255;
	blend.AlphaFormat = AC_SRC_ALPHA;
 
	POINT ptSrc = {10, 10 };
	SIZE sz = { 100, 100 };
	UpdateLayeredWindow(hwnd, NULL, NULL, &sz, dcMem, &ptSrc, RGB(255,255,255), &blend, ULW_COLORKEY );
	DWORD dwError = GetLastError(); // <- this gives me 87
 
	DeleteDC(dcMem);
	DeleteObject(pDC);
}

thank you

i wish that was it but no, still get 87, it compiles and runs fine is just the UpdateLayeredWindow is doing nothing to the window.

yes i am using WS_EX_LAYERED
and UpdateLayeredWindow is returning 0, is failing.

#define WIN32_LEAN_AND_MEAN

#ifndef WS_EX_LAYERED
#define WS_EX_LAYERED 0x00080000
#endif

#ifndef LWA_COLORKEY
#define LWA_COLORKEY 0x00000001
#define LWA_ALPHA 0x00000002
#endif

#include <windows.h>
#include "resource.h"

HINSTANCE aInstance;

void update(HWND hwnd);
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);

int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prev, char *args, int show) {
HWND hwnd; //window handle
MSG msg; //message
WNDCLASSEX windowClass; //window class
windowClass.cbSize = sizeof(WNDCLASSEX);
windowClass.style = CS_HREDRAW | CS_VREDRAW ;
windowClass.lpfnWndProc = WndProc;
windowClass.cbClsExtra = 0;
windowClass.cbWndExtra = 0;
windowClass.hInstance = instance;
windowClass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
windowClass.hCursor = LoadCursor(NULL, IDI_APPLICATION);
windowClass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);//(HBRUSH)GetStockObject(NewBrush); set window background colour
windowClass.lpszMenuName = NULL;//MAKEINTRESOURCE(IDR_MENU1); //add menu bar
windowClass.lpszClassName = "MyClass";
windowClass.hIconSm = LoadIcon(GetModuleHandle(NULL), MAKEINTRESOURCE(IDI_ICON1));

//register the window class
if(!RegisterClassEx(&windowClass))
return 0;

hwnd = CreateWindowEx(WS_EX_LAYERED,
"MyClass",
"Test",
WS_OVERLAPPEDWINDOW |
//WS_MINIMIZEBOX|
WS_VISIBLE |
WS_SYSMENU,
200, 100,
400, 350,
NULL,
NULL,
instance,
NULL);


MSG message;

while (GetMessage(&message, 0, 0, 0)) {
TranslateMessage(&message);
DispatchMessage(&message);
}

return message.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam){

switch(message){
case WM_CREATE:
SetLayeredWindowAttributes(hwnd, 0, 240, LWA_ALPHA);
update(hwnd);
return 0;
case WM_CLOSE:
DestroyWindow(hwnd);
//ShowWindow(window, SW_HIDE );
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;

break;
default:
break;
}
return (DefWindowProc(hwnd, message, wParam, lParam));
}

void update(HWND hwnd){
HDC pDC = GetDC(hwnd);
HDC dcMem;
dcMem = CreateCompatibleDC(pDC);
COLORREF colour;
colour = RGB(255,255,255);
HBITMAP bmp;
//bmp = LoadBitmap(aInstance, "clockbg.bmp");
bmp = LoadBitmap(GetModuleHandle(NULL), MAKEINTRESOURCE(IDB_BITMAP1));
if(!bmp)MessageBox(NULL,"FAIL TO LOAD IMAGE", "ERROR",NULL);

HBITMAP pOldBitmap = (HBITMAP) SelectObject(dcMem, dcMem);
BLENDFUNCTION blend;
blend.BlendOp = AC_SRC_OVER;
blend.BlendFlags = 0;
blend.SourceConstantAlpha = 255;
blend.AlphaFormat = AC_SRC_ALPHA;

POINT ptSrc = {10, 10 };
SIZE sz = { 100, 100 };
//UpdateLayeredWindow(hwnd, NULL, NULL, &sz, dcMem, &ptSrc, colour, &blend, LWA_ALPHA );
int p = UpdateLayeredWindow(hwnd, NULL, NULL, NULL, dcMem, NULL, colour, &blend, LWA_ALPHA );
DWORD dwError = GetLastError(); // <- this gives me 87

DeleteDC(dcMem);
DeleteObject(pDC);
}