Transparent button WinAPI C++

Question

I have a simple window, my main window contains WS_EX_LAYERED flag. I can change opacity of main window but when I try to change opacity of children window I'll get some problem. It's not visible. Maybe I should use another flag in CreateWindowEx(..) or use post-fix A or W? I just need visible main window with 100 percentage of opacity and the button, which can change opacity.

#include <windows.h>

LPCWSTR g_szClassName = L"myWindowClass";

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    case WM_CLOSE:
        DestroyWindow(hwnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;
    default:
        return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASSEX wc;
    HWND hwnd, btn;
    MSG Msg;

    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style = 0;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = g_szClassName;
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

    if (!RegisterClassEx(&wc))
    {
        MessageBox(NULL, L"Window Registration Failed!", L"Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    hwnd = CreateWindowEx(
        WS_EX_LAYERED,
        g_szClassName,
        L"The title of my window",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 600, 600,
        NULL, NULL, hInstance, NULL);

    btn = CreateWindowEx(
        WS_EX_LAYERED,
        L"BUTTON",                                                                  
        L"TEXT",                                                                    
        WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,                                      
        0,
        0,                                                                  
        100,                                                                
        100,                                                                
        hwnd,                                                                       
        (HMENU)BN_CLICKED,                                                          
        (HINSTANCE)GetWindowLongPtr(hwnd, GWLP_HINSTANCE),
        NULL);                                                                      

    SetLayeredWindowAttributes(hwnd, 0, 255, LWA_ALPHA);
    SetLayeredWindowAttributes(btn, 0, 50, LWA_ALPHA);
    if (hwnd == NULL)
    {
        MessageBox(NULL, L"Window Creation Failed!", L"Error!",
            MB_ICONEXCLAMATION | MB_OK);
        return 0;
    }

    ShowWindow(hwnd, nCmdShow);
    ShowWindow(btn, nCmdShow);
    UpdateWindow(hwnd);

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

Answer 1

First you need to add a manifest file in the application directory to specify Windows 8 compatibility.

<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
  <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1"> 
    <application>
      <!--The ID below indicates app support for Windows 8 -->
      <supportedOS Id="{4a2f28e3-53b9-4441-ba9c-d69d4a4a6e38}"/>
    </application>
  </compatibility>
  <dependency>
    <dependentAssembly>
        <assemblyIdentity
            type="win32"
            name="Microsoft.Windows.Common-Controls"
            version="6.0.0.0"
            processorArchitecture="*"
            publicKeyToken="6595b64144ccf1df"
            language="*"
        />
    </dependentAssembly>
  </dependency>
</assembly>

Then specify the use of the manifest file. If you are using VS, you can set it in Properties->Manifest Tool->Input and Out->Additional Manifest Files.

Finally rebuild the project,output: