Drawing custom desktop background (Windows)

// Note: Loading image resources and processing keyboard input is
// not required, that's just how I demoed it. After FindWindowA,
// just make a loop where you draw whatever you want at any interval
// - don't worry, Windows won't try to draw over you.
// Does not work with Wallpaper Engine running.

// Edited 06-Jun-2019 for Windows 10 compatibility

#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <assert.h>
#include "resource.h"

BOOL CALLBACK WorkerEnumProc(HWND hWnd, LPARAM lParam);

DWORD __stdcall WinMain(HINSTANCE hInstance, HINSTANCE hPrevInst,
    PSZ pszCmdLine, int nCmdShow) {
    HANDLE hDC, hMemDC;
    HGDIOBJ hOldBitmap;
    HWND hWndDesktop;
    HBITMAP hBitmapImage;
    BITMAP bmImage;
    SHORT sShiftLast = 0xFFFF, sShiftCur;
    int iOldMode, iScreenW, iScreenH;

    hBitmapImage = LoadImageA(hInstance, MAKEINTRESOURCEA(IDB_RAW),
        IMAGE_BITMAP, 0, 0, 0);
    assert(hBitmapImage);
    GetObject(hBitmapImage, sizeof(BITMAP), &bmImage);

    iScreenW = GetSystemMetrics(SM_CXSCREEN);
    iScreenH = GetSystemMetrics(SM_CYSCREEN);

    hWndProgman = FindWindowA("Progman", NULL);
    if (!hWndProgman) {
        MessageBoxA(NULL, "Unable to find program manager window",
            "Error", MB_ICONERROR);
        ExitProcess(1);
    }

    if ((GetVersion() & 0x0000FFFF) == 0x0206) {
        // Windows 8.1+
        OutputDebugStringA("Windows 8.1 or later detected\r\n");
        SendMessage(hWndProgman, 0x052C, 0, 0);
        EnumWindows(WorkerEnumProc, (LPARAM)&hWndDesktop);
    } else {
        // Any earlier version
        OutputDebugStringA("Windows 8 or earlier detected\r\n");
        hWndDesktop = hWndProgman;
    }

    if (!hWndDesktop) {
        MessageBoxA(NULL, "Unable to find desktop window",
            "Error", MB_ICONERROR);
        ExitProcess(1);
    }

    // my loop. put whatever you want in yours.
    // all you need is to GetDC(hWndDesktop), draw, and ReleaseDC(hWndDesktop, hDC) each time
    while (!(GetAsyncKeyState(VK_END) & 0x8000)) {
        sShiftCur = GetAsyncKeyState(VK_SHIFT) & 0x8000;
        if (sShiftCur != sShiftLast) {
            hBitmapImage = LoadImageA(hInstance,
                MAKEINTRESOURCEA(sShiftCur ? IDB_ACTIVATED : IDB_RAW),
                IMAGE_BITMAP, 0, 0, 0);
            assert(hBitmapImage);
            GetObject(hBitmapImage, sizeof(BITMAP), &bmImage);
            sShiftLast = sShiftCur;


            hDC = GetDC(hWndDesktop);
            hMemDC = CreateCompatibleDC(hDC);
            hOldBitmap = SelectObject(hMemDC, hBitmapImage);
            iOldMode = SetStretchBltMode(hDC, HALFTONE);
            StretchBlt(hDC, 0, 0, iScreenW, iScreenH, hMemDC, 0, 0,
                bmImage.bmWidth, bmImage.bmHeight, SRCCOPY);
            SetStretchBltMode(hDC, iOldMode);
            SelectObject(hMemDC, hOldBitmap);
            ReleaseDC(hWndDesktop, hDC);
        }


        Sleep(50);
    }

    return 0;
}

BOOL CALLBACK WorkerEnumProc(HWND hWnd, LPARAM lParam) {
    HWND hWndDefView;

    hWndDefView = FindWindowExA(hWnd, NULL, "SHELLDLL_DefView",
        NULL);
    if (hWndDefView) {
        *(HWND*)lParam = FindWindowExA(NULL, hWnd, "WorkerW",
            NULL);
        return FALSE;
    }

    return TRUE;
}