layeredwnd.cpp

#define NOMINMAX
#define STRICT
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <Siv3D.hpp>


struct DIBSection
{
	HDC hdc;
	HBITMAP hbmp;
	HBITMAP old;
	LPBYTE bits;

	DIBSection(const Size& size)
	{
		BITMAPINFO bi {};
		bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
		bi.bmiHeader.biBitCount = 32;
		bi.bmiHeader.biPlanes = 1;
		bi.bmiHeader.biWidth = size.x;
		bi.bmiHeader.biHeight = -size.y;

		hbmp = ::CreateDIBSection(NULL, &bi, DIB_RGB_COLORS, (void**)&bits, NULL, 0);

		HDC hDesktopDc = ::GetDC(0);
		hdc = ::CreateCompatibleDC(hDesktopDc);
		::ReleaseDC(0, hDesktopDc);

		old = (HBITMAP)::SelectObject(hdc, hbmp);
	}

	~DIBSection()
	{
		::SelectObject(hdc, old);
		::DeleteDC(hdc);
		::DeleteObject(hbmp);
	}
};


void copyImageBits(Image& imgSrc, LPBYTE bitsDst)
{
	for (int i : step(imgSrc.height))
	{
		for (int j : step(imgSrc.width))
		{
			bitsDst[i * imgSrc.width * 4 + j * 4 + 0] = imgSrc[i][j].b;
			bitsDst[i * imgSrc.width * 4 + j * 4 + 1] = imgSrc[i][j].g;
			bitsDst[i * imgSrc.width * 4 + j * 4 + 2] = imgSrc[i][j].r;
			bitsDst[i * imgSrc.width * 4 + j * 4 + 3] = imgSrc[i][j].a;
		}
	}
}

LRESULT CALLBACK windowProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
	switch (msg)
	{
	case WM_NCHITTEST:
		return HTCAPTION;
	}

	return ::DefWindowProc(hwnd, msg, wparam, lparam);
}

HWND createSubWindow(const Size& size)
{
	// ウィンドウクラスの登録

	const String className = L"wnd";

	WNDCLASS wc {};
	wc.lpfnWndProc   = windowProc;
	wc.hInstance     = ::GetModuleHandle(NULL);
	wc.lpszClassName = className.c_str();

	if (::RegisterClass(&wc) == 0)
	{
		MessageBox::Show(L"ウィンドウクラスの登録に失敗しました。");
		return NULL;
	}


	// ウィンドウを作成

	HWND hwnd = ::CreateWindowEx(
		WS_EX_LAYERED | WS_EX_TOOLWINDOW,
		className.c_str(),
		L"Siv3D & ULW Test App",
		WS_POPUP,
		0, 0, size.x, size.y,
		NULL,
		NULL,
		::GetModuleHandle(NULL),
		NULL);

	if (hwnd == NULL)
	{
		MessageBox::Show(L"ウィンドウ作成に失敗しました。");
		return NULL;
	}

	return hwnd;
}

void updateLayeredWindow(HWND hwnd, HDC hdc)
{
	BLENDFUNCTION blend;
	blend.BlendOp = AC_SRC_OVER;
	blend.BlendFlags = 0;
	blend.SourceConstantAlpha = 255;
	blend.AlphaFormat = AC_SRC_ALPHA;

	RECT rect;
	::GetWindowRect(hwnd, &rect);

	POINT point;
	point.x = rect.left;
	point.y = rect.top;

	SIZE size;
	size.cx = rect.right - rect.left;
	size.cy = rect.bottom - rect.top;

	POINT p {};

	HDC hDesktopDc = ::GetDC(0);
	::UpdateLayeredWindow(hwnd, hDesktopDc, &point, &size, hdc, &p, 0, &blend, ULW_ALPHA);
	::ReleaseDC(0, hDesktopDc);
}

void Main()
{
	Image img(L"Example/Siv3D-kun.png");


	HWND hwnd = createSubWindow(img.size);
	if (hwnd == NULL)
	{
		return;
	}

	::ShowWindow(hwnd, SW_SHOWNORMAL);


	DIBSection dib(img.size);
	
	copyImageBits(img, dib.bits);

	updateLayeredWindow(hwnd, dib.hdc);


	while (true)
	{
		MSG msg = { };

		if (PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE))
		{
			if (GetMessage(&msg, NULL, 0, 0))
			{
				TranslateMessage(&msg);
				DispatchMessage(&msg);
			}
		}
		else {
			if (!System::Update())
			{
				break;
			}

			Window::ClientRect().draw(Palette::Black);
		}
	}
}