Wallpaper test

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

static const char SZ_CLASSNAME[] = "DEXTOP";

static BOOL s_bActivated = FALSE;
static HBITMAP s_hCurBitmap = NULL;
static HINSTANCE s_hInstance;
static BITMAP s_bmCurBitmap;

DWORD __stdcall STWinProc(HWND hWnd, UINT uMsg, WPARAM wParam,
        LPARAM lParam) {
    switch (uMsg) {
    case WM_CREATE:
        s_hCurBitmap = LoadImageA(s_hInstance,
            MAKEINTRESOURCEA(IDB_ALMONDS_RAW),
            IMAGE_BITMAP, 0, 0, 0);
        assert(s_hCurBitmap);
        GetObject(s_hCurBitmap, sizeof(BITMAP), &s_bmCurBitmap);
        return 0;

    case WM_LBUTTONDOWN:
        s_bActivated = !s_bActivated;
        if (s_bActivated) s_hCurBitmap = LoadImageA(s_hInstance,
                MAKEINTRESOURCEA(IDB_ALMONDS_ACTIVATED),
                IMAGE_BITMAP, 0, 0, 0);
        else s_hCurBitmap = LoadImageA(s_hInstance,
                MAKEINTRESOURCEA(IDB_ALMONDS_RAW),
                IMAGE_BITMAP, 0, 0, 0);
        assert(s_hCurBitmap);
        GetObject(s_hCurBitmap, sizeof(BITMAP), &s_bmCurBitmap);
        InvalidateRect(hWnd, NULL, FALSE);
        return 0;

    case WM_PAINT:
    {
        HANDLE hDC, hMemDC;
        HGDIOBJ hOldBitmap;
        PAINTSTRUCT ps;
        int iOldMode;
        RECT rectClient;

        assert(GetClientRect(hWnd, &rectClient));
        hDC = BeginPaint(hWnd, &ps);
        hMemDC = CreateCompatibleDC(hDC);
        hOldBitmap = SelectObject(hMemDC, s_hCurBitmap);
        iOldMode = SetStretchBltMode(hDC, HALFTONE);
        StretchBlt(hDC, rectClient.left, rectClient.top,
            rectClient.right - rectClient.left,
            rectClient.bottom - rectClient.top, hMemDC, 0, 0,
            s_bmCurBitmap.bmWidth, s_bmCurBitmap.bmHeight,
            SRCCOPY);
        SetStretchBltMode(hDC, iOldMode);
        SelectObject(hMemDC, hOldBitmap);
        DeleteDC(hMemDC);
        EndPaint(hWnd, &ps);

        return 0;
    }

    case WM_SIZE:
        InvalidateRect(hWnd, NULL, FALSE);
        return 0;

    case WM_CLOSE:
        DestroyWindow(hWnd);
        return 0;

    case WM_DESTROY:
        ExitProcess(0);
        return 0;
    }

    return DefWindowProc(hWnd, uMsg, wParam, lParam);
}

DWORD __stdcall WinMain(HINSTANCE hInstance, HINSTANCE hPrevInst,
        PSZ pszCmdLine, int nCmdShow) {
    HANDLE hWnd;
    MSG msg;
    WNDCLASSEXA wcxa = {
        sizeof(WNDCLASSEXA),
        0,
        STWinProc,
        0, 0,
        hInstance,
        LoadIconA(NULL, MAKEINTRESOURCEA(IDI_APPLICATION)),
        LoadCursorA(NULL, MAKEINTRESOURCEA(IDC_ARROW)),
        GetSysColorBrush(COLOR_BACKGROUND),
        NULL, SZ_CLASSNAME, NULL
    };

    s_hInstance = hInstance;
    assert(RegisterClassExA(&wcxa));
    hWnd = CreateWindowA(SZ_CLASSNAME, "Background",
        WS_OVERLAPPEDWINDOW | WS_VISIBLE, 100, 100, 200, 200, NULL, NULL,
        hInstance, 0);

    ShowWindow(hWnd, SW_SHOW);

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