仿照VS工具實現窗口陰影

原理：創建四個窗口平鋪在需要添加陰影的窗口上；

vs實現原理：可以使用QQ截圖放在vs工具的四周可看出實現原理；

頭文件：

#include <QtWidgets/QMainWindow>

#define int32 int
using float64 = double;
typedef unsigned int quint32;
using uint32 = quint32;
using ShiftedMultiplier = uint32;

namespace Main_Window {
	enum class ShadowsChange {
		Moved = 0x01,
		Resized = 0x02,
		Shown = 0x04,
		Hidden = 0x08,
		Activate = 0x10,
	};
	Q_DECLARE_FLAGS(ShadowsChanges, ShadowsChange);
}


enum {
	_PsInitHor = 0x01,
	_PsInitVer = 0x02,
};


#define for_const(range_declaration, range_expression) for (range_declaration : std::as_const(range_expression))
#include <QPainter>

#include <Shobjidl.h>
#include <shellapi.h>
#include <WtsApi32.h>

#include <Windowsx.h>
#include <gdiplus.h>

class _PsShadowWindows {
public:
	using Change = Main_Window::ShadowsChange;
	using Changes = Main_Window::ShadowsChanges;

	_PsShadowWindows();
	~_PsShadowWindows();

	void setColor(QColor c);
	bool init(QColor c);
	void initCorners(int directions = (_PsInitHor | _PsInitVer));
	void verCorners(int h, Gdiplus::Graphics *pgraphics1, Gdiplus::Graphics *pgraphics3);
	void horCorners(int w, Gdiplus::Graphics *pgraphics0, Gdiplus::Graphics *pgraphics2);
	void update(Changes changes, WINDOWPOS *pos = 0);
	void updateWindow(int i, POINT *p, SIZE *s = 0);
	void destroy();
	//void setApp(myDialog* d);
	static void setApp(QWidget* d);
	static void setResizeEnable(bool flag);
private:

	int _x, _y, _w, _h;
	int _metaSize, _fullsize, _size, _shift;
	QVector<BYTE> _alphas, _colors;

	bool hidden;

	HWND hwnds[4];;
	static QWidget* m_myApp;
	static bool m_bRsizeEnable;
	static bool m_bNCactivate;
	HDC dcs[4], screenDC;
	HBITMAP bitmaps[4];
	int max_w, max_h;
	BLENDFUNCTION blend;

	BYTE r, g, b;
	COLORREF noKeyColor;

	static LRESULT __stdcall wndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
};

extern _PsShadowWindows _psShadowWindows;

實現：

#include "shadow_win.h"
#include <QCoreApplication>

int32 _psSize = 0;
QWidget* _PsShadowWindows::m_myApp = NULL;
bool _PsShadowWindows::m_bRsizeEnable = true;
bool _PsShadowWindows::m_bNCactivate = true;
#pragma comment(lib,"gdiplus.lib")

_PsShadowWindows::_PsShadowWindows() : screenDC(0), max_w(0), max_h(0), _x(0), _y(0), _w(0), _h(0), hidden(true), r(0), g(0), b(0), noKeyColor(RGB(255, 255, 255)) {
		for (int i = 0; i < 4; ++i) {
			dcs[i] = 0;
			bitmaps[i] = 0;
			hwnds[i] = 0;
		}
	}

_PsShadowWindows::~_PsShadowWindows()
{
}

	void _PsShadowWindows::setColor(QColor c) {
		r = c.red();
		g = c.green();
		b = c.blue();

		if (!hwnds[0]) return;
		Gdiplus::SolidBrush brush(Gdiplus::Color(_alphas[0], r, g, b));
		for (int i = 0; i < 4; ++i) {
			Gdiplus::Graphics graphics(dcs[i]);
			graphics.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);
			if ((i % 2) && _h || !(i % 2) && _w) {
				graphics.FillRectangle(&brush, 0, 0, (i % 2) ? _size : _w, (i % 2) ? _h : _size);
			}
		}
		initCorners();

		_x = _y = _w = _h = 0;
		update( (Change)(0x01 | 0x02));
	}

	bool _PsShadowWindows::init(QColor c) {
		_fullsize = 19;
		_shift = 1;
		auto cornersImage = QImage(_fullsize, _fullsize, QImage::Format_ARGB32_Premultiplied);
		
		QCoreApplication::applicationDirPath();
		cornersImage.load(QCoreApplication::applicationDirPath() + "\\Resources\\shadow.png");

		_metaSize = _fullsize + 2 * _shift;
		_alphas.reserve(_metaSize);
		_colors.reserve(_metaSize * _metaSize);
		for (int32 j = 0; j < _metaSize; ++j) {
			for (int32 i = 0; i < _metaSize; ++i) {
				_colors.push_back((i < 2 * _shift || j < 2 * _shift) ? 1 : qMax(BYTE(1), BYTE(cornersImage.pixel(QPoint(i - 2 * _shift, j - 2 * _shift)) >> 24)));
			}
		}
		uchar prev = 0;
		for (int32 i = 0; i < _metaSize; ++i) {
			uchar a = _colors[(_metaSize - 1) * _metaSize + i];
			if (a < prev) break;

			_alphas.push_back(a);
			prev = a;
		}
		_psSize = _size = _alphas.size() - 2 * _shift;

		setColor(c);

		Gdiplus::GdiplusStartupInput gdiplusStartupInput;
		ULONG_PTR gdiplusToken;
		Gdiplus::Status gdiRes = Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);

		if (gdiRes != Gdiplus::Ok) {
			return false;
		}
		blend.AlphaFormat = AC_SRC_ALPHA;
		blend.SourceConstantAlpha = 255;
		blend.BlendFlags = 0;
		blend.BlendOp = AC_SRC_OVER;

		screenDC = GetDC(0);
		if (!screenDC) {
			return false;
		}

		QRect avail(m_myApp->geometry());
		max_w = avail.width();
		max(max_w, 19);
		max_h = avail.height();
		//max(max_h, st::titleHeight + st::windowMinHeight);

		HINSTANCE appinst = (HINSTANCE)GetModuleHandle(0);
		HWND hwnd = (HWND)m_myApp->winId() ? (HWND)m_myApp->winId() : 0;

		for (int i = 0; i < 4; ++i) {
			QString cn = QString("TelegramShadow%1").arg(i);
			LPCWSTR _cn = (LPCWSTR)cn.utf16();
			WNDCLASSEX wc;

			wc.cbSize = sizeof(wc);
			wc.style = 0;
			wc.lpfnWndProc = wndProc;
			wc.cbClsExtra = 0;
			wc.cbWndExtra = 0;
			wc.hInstance = appinst;
			wc.hIcon = 0;
			wc.hCursor = 0;
			wc.hbrBackground = 0;
			wc.lpszMenuName = NULL;
			wc.lpszClassName = _cn;
			wc.hIconSm = 0;
			if (!RegisterClassEx(&wc)) {
				destroy();
				return false;
			}

			hwnds[i] = CreateWindowEx(WS_EX_LAYERED | WS_EX_TOOLWINDOW, _cn, 0, WS_POPUP, 0, 0, 0, 0, 0, 0, appinst, 0);
			if (!hwnds[i]) {
				destroy();
				return false;
			}
			SetWindowLong(hwnds[i], GWL_HWNDPARENT, (LONG)hwnd);

			dcs[i] = CreateCompatibleDC(screenDC);
			if (!dcs[i]) {
				destroy();
				return false;
			}

			bitmaps[i] = CreateCompatibleBitmap(screenDC, (i % 2) ? _size : max_w, (i % 2) ? max_h : _size);
			if (!bitmaps[i]) {
				destroy();
				return false;
			}

			SelectObject(dcs[i], bitmaps[i]);
		}

		QStringList alphasForLog;
		for_const(auto alpha, _alphas) {
			alphasForLog.append(QString::number(alpha));
		}

		initCorners();
		return true;
	}

	void _PsShadowWindows::initCorners(int directions ) {
		bool hor = (directions & _PsInitHor), ver = (directions & _PsInitVer);
		Gdiplus::Graphics graphics0(dcs[0]), graphics1(dcs[1]), graphics2(dcs[2]), graphics3(dcs[3]);
		graphics0.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);
		graphics1.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);
		graphics2.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);
		graphics3.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);

		Gdiplus::SolidBrush brush(Gdiplus::Color(_alphas[0], r, g, b));
		if (hor) graphics0.FillRectangle(&brush, 0, 0, _fullsize - (_size - _shift), 2 * _shift);

		if (ver) {
			graphics1.FillRectangle(&brush, 0, 0, _size, 2 * _shift);
			graphics3.FillRectangle(&brush, 0, 0, _size, 2 * _shift);
			graphics1.FillRectangle(&brush, _size - _shift, 2 * _shift, _shift, _fullsize);
			graphics3.FillRectangle(&brush, 0, 2 * _shift, _shift, _fullsize);
		}

		if (hor) {
			for (int j = 2 * _shift; j < _size; ++j) {
				for (int k = 0; k < _fullsize - (_size - _shift); ++k) {
					brush.SetColor(Gdiplus::Color(_colors[j * _metaSize + k + (_size + _shift)], r, g, b));
					graphics0.FillRectangle(&brush, k, j, 1, 1);
					graphics2.FillRectangle(&brush, k, _size - (j - 2 * _shift) - 1, 1, 1);
				}
			}
			for (int j = _size; j < _size + 2 * _shift; ++j) {
				for (int k = 0; k < _fullsize - (_size - _shift); ++k) {
					brush.SetColor(Gdiplus::Color(_colors[j * _metaSize + k + (_size + _shift)], r, g, b));
					graphics2.FillRectangle(&brush, k, _size - (j - 2 * _shift) - 1, 1, 1);
				}
			}
		}
		if (ver) {
			for (int j = 2 * _shift; j < _fullsize + 2 * _shift; ++j) {
				for (int k = _shift; k < _size; ++k) {
					brush.SetColor(Gdiplus::Color(_colors[j * _metaSize + (k + _shift)], r, g, b));
					graphics1.FillRectangle(&brush, _size - k - 1, j, 1, 1);
					graphics3.FillRectangle(&brush, k, j, 1, 1);
				}
			}
		}
	}
	void _PsShadowWindows::verCorners(int h, Gdiplus::Graphics *pgraphics1, Gdiplus::Graphics *pgraphics3) {
		Gdiplus::SolidBrush brush(Gdiplus::Color(_alphas[0], r, g, b));
		pgraphics1->FillRectangle(&brush, _size - _shift, h - _fullsize, _shift, _fullsize);
		pgraphics3->FillRectangle(&brush, 0, h - _fullsize, _shift, _fullsize);
		for (int j = 0; j < _fullsize; ++j) {
			for (int k = _shift; k < _size; ++k) {
				brush.SetColor(Gdiplus::Color(_colors[(j + 2 * _shift) * _metaSize + k + _shift], r, g, b));
				pgraphics1->FillRectangle(&brush, _size - k - 1, h - j - 1, 1, 1);
				pgraphics3->FillRectangle(&brush, k, h - j - 1, 1, 1);
			}
		}
	}
	void _PsShadowWindows::horCorners(int w, Gdiplus::Graphics *pgraphics0, Gdiplus::Graphics *pgraphics2) {
		Gdiplus::SolidBrush brush(Gdiplus::Color(_alphas[0], r, g, b));
		pgraphics0->FillRectangle(&brush, w - 2 * _size - (_fullsize - (_size - _shift)), 0, _fullsize - (_size - _shift), 2 * _shift);
		for (int j = 2 * _shift; j < _size; ++j) {
			for (int k = 0; k < _fullsize - (_size - _shift); ++k) {
				brush.SetColor(Gdiplus::Color(_colors[j * _metaSize + k + (_size + _shift)], r, g, b));
				pgraphics0->FillRectangle(&brush, w - 2 * _size - k - 1, j, 1, 1);
				pgraphics2->FillRectangle(&brush, w - 2 * _size - k - 1, _size - (j - 2 * _shift) - 1, 1, 1);
			}
		}
		for (int j = _size; j < _size + 2 * _shift; ++j) {
			for (int k = 0; k < _fullsize - (_size - _shift); ++k) {
				brush.SetColor(Gdiplus::Color(_colors[j * _metaSize + k + (_size + _shift)], r, g, b));
				pgraphics2->FillRectangle(&brush, w - 2 * _size - k - 1, _size - (j - 2 * _shift) - 1, 1, 1);
			}
		}
	}

	void _PsShadowWindows::update(Changes changes, WINDOWPOS *pos) {

		HWND hwnd = (HWND)m_myApp->winId() ? (HWND)m_myApp->winId() : 0; 
		if (!hwnd || !hwnds[0]) return;

		if (changes == Changes(Change::Activate)) {
			for (int i = 0; i < 4; ++i) {
				SetWindowPos(hwnds[i], hwnd, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
			}
			return;
		}

		if (changes & Change::Hidden) {
			if (!hidden) {
				for (int i = 0; i < 4; ++i) {
					hidden = true;
					ShowWindow(hwnds[i], SW_HIDE);
				}
			}
			return;
		}
		if (!m_myApp->isVisible()) return;

		int x = _x, y = _y, w = _w, h = _h;
		/*if (pos && (!(pos->flags & SWP_NOMOVE) || !(pos->flags & SWP_NOSIZE) || !(pos->flags & SWP_NOREPOSITION))) {
			if (!(pos->flags & SWP_NOMOVE)) {
				x = pos->x - _size;
				y = pos->y - _size;
			}
			else if (pos->flags & SWP_NOSIZE) {
				for (int i = 0; i < 4; ++i) {
					SetWindowPos(hwnds[i], hwnd, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
				}
				return;
			}
			if (!(pos->flags & SWP_NOSIZE)) {
				w = pos->cx + 2 * _size;
				h = pos->cy + 2 * _size;
			}
		}
		else*/ {
			RECT r;
			GetWindowRect(hwnd, &r);
			x = r.left - _size;
			y = r.top - _size;
			w = r.right + _size - x;
			h = r.bottom + _size - y;
		}
		if (h < 2 * _fullsize + 2 * _shift) {
			h = 2 * _fullsize + 2 * _shift;
		}
		if (w < 2 * (_fullsize + _shift)) {
			w = 2 * (_fullsize + _shift);
		}

		if (w != _w) {
			int from = (_w > 2 * (_fullsize + _shift)) ? (_w - _size - _fullsize - _shift) : (_fullsize - (_size - _shift));
			int to = w - _size - _fullsize - _shift;
			if (w > max_w) {
				from = _fullsize - (_size - _shift);
				max_w *= 2;
				for (int i = 0; i < 4; i += 2) {
					DeleteObject(bitmaps[i]);
					bitmaps[i] = CreateCompatibleBitmap(screenDC, max_w, _size);
					SelectObject(dcs[i], bitmaps[i]);
				}
				initCorners(_PsInitHor);
			}
			Gdiplus::Graphics graphics0(dcs[0]), graphics2(dcs[2]);
			graphics0.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);
			graphics2.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);
			Gdiplus::SolidBrush brush(Gdiplus::Color(_alphas[0], r, g, b));
			if (to > from) {
				graphics0.FillRectangle(&brush, from, 0, to - from, 2 * _shift);
				for (int i = 2 * _shift; i < _size; ++i) {
					Gdiplus::Pen pen(Gdiplus::Color(_alphas[i], r, g, b));
					graphics0.DrawLine(&pen, from, i, to, i);
					graphics2.DrawLine(&pen, from, _size - (i - 2 * _shift) - 1, to, _size - (i - 2 * _shift) - 1);
				}
				for (int i = _size; i < _size + 2 * _shift; ++i) {
					Gdiplus::Pen pen(Gdiplus::Color(_alphas[i], r, g, b));
					graphics2.DrawLine(&pen, from, _size - (i - 2 * _shift) - 1, to, _size - (i - 2 * _shift) - 1);
				}
			}
			if (_w > w) {
				graphics0.FillRectangle(&brush, w - _size - _fullsize - _shift, 0, _fullsize - (_size - _shift), _size);
				graphics2.FillRectangle(&brush, w - _size - _fullsize - _shift, 0, _fullsize - (_size - _shift), _size);
			}
			horCorners(w, &graphics0, &graphics2);
			POINT p0 = { x + _size, y }, p2 = { x + _size, y + h - _size }, f = { 0, 0 };
			SIZE s = { w - 2 * _size, _size };
			updateWindow(0, &p0, &s);
			updateWindow(2, &p2, &s);
		}
		else if (x != _x || y != _y) {
			POINT p0 = { x + _size, y }, p2 = { x + _size, y + h - _size };
			updateWindow(0, &p0);
			updateWindow(2, &p2);
		}
		else if (h != _h) {
			POINT p2 = { x + _size, y + h - _size };
			updateWindow(2, &p2);
		}

		if (h != _h) {
			int from = (_h > 2 * _fullsize + 2 * _shift) ? (_h - _fullsize) : (_fullsize + 2 * _shift);
			int to = h - _fullsize;
			if (h > max_h) {
				from = (_fullsize + 2 * _shift);
				max_h *= 2;
				for (int i = 1; i < 4; i += 2) {
					DeleteObject(bitmaps[i]);
					bitmaps[i] = CreateCompatibleBitmap(dcs[i], _size, max_h);
					SelectObject(dcs[i], bitmaps[i]);
				}
				initCorners(_PsInitVer);
			}
			Gdiplus::Graphics graphics1(dcs[1]), graphics3(dcs[3]);
			graphics1.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);
			graphics3.SetCompositingMode(Gdiplus::CompositingModeSourceCopy);

			Gdiplus::SolidBrush brush(Gdiplus::Color(_alphas[0], r, g, b));
			if (to > from) {
				graphics1.FillRectangle(&brush, _size - _shift, from, _shift, to - from);
				graphics3.FillRectangle(&brush, 0, from, _shift, to - from);
				for (int i = 2 * _shift; i < _size + _shift; ++i) {
					Gdiplus::Pen pen(Gdiplus::Color(_alphas[i], r, g, b));
					graphics1.DrawLine(&pen, _size + _shift - i - 1, from, _size + _shift - i - 1, to);
					graphics3.DrawLine(&pen, i - _shift, from, i - _shift, to);
				}
			}
			if (_h > h) {
				graphics1.FillRectangle(&brush, 0, h - _fullsize, _size, _fullsize);
				graphics3.FillRectangle(&brush, 0, h - _fullsize, _size, _fullsize);
			}
			verCorners(h, &graphics1, &graphics3);

			POINT p1 = { x + w - _size, y }, p3 = { x, y }, f = { 0, 0 };
			SIZE s = { _size, h };
			updateWindow(1, &p1, &s);
			updateWindow(3, &p3, &s);
		}
		else if (x != _x || y != _y) {
			POINT p1 = { x + w - _size, y }, p3 = { x, y };
			updateWindow(1, &p1);
			updateWindow(3, &p3);
		}
		else if (w != _w) {
			POINT p1 = { x + w - _size, y };
			updateWindow(1, &p1);
		}
		_x = x;
		_y = y;
		_w = w;
		_h = h;

		if (hidden && (changes & Change::Shown)) {
			for (int i = 0; i < 4; ++i) {
				SetWindowPos(hwnds[i], hwnd, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_SHOWWINDOW | SWP_NOACTIVATE);
			}
			hidden = false;
		}
	}

	void _PsShadowWindows::updateWindow(int i, POINT *p, SIZE *s) {
		static POINT f = { 0, 0 };
		if (s) {
			UpdateLayeredWindow(hwnds[i], (s ? screenDC : 0), p, s, (s ? dcs[i] : 0), (s ? (&f) : 0), noKeyColor, &blend, ULW_ALPHA);
		}
		else {
			SetWindowPos(hwnds[i], 0, p->x, p->y, 0, 0, SWP_NOACTIVATE | SWP_NOSIZE | SWP_NOZORDER);
		}
	}

	void _PsShadowWindows::destroy() {
		for (int i = 0; i < 4; ++i) {
			if (dcs[i]) DeleteDC(dcs[i]);
			if (bitmaps[i]) DeleteObject(bitmaps[i]);
			if (hwnds[i]) DestroyWindow(hwnds[i]);
			dcs[i] = 0;
			bitmaps[i] = 0;
			hwnds[i] = 0;
		}
		if (screenDC) ReleaseDC(0, screenDC);
	}

void _PsShadowWindows::setApp(QWidget* d) {
		m_myApp = d;
	}

void _PsShadowWindows::setResizeEnable(bool flag)
{
	m_bRsizeEnable = flag;
}


LRESULT __stdcall _PsShadowWindows::wndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
	auto wnd = m_myApp;
	if (!wnd) return DefWindowProc(hwnd, msg, wParam, lParam);
	if (!m_bRsizeEnable) return DefWindowProc(hwnd, msg, wParam, lParam);

	int i;
	for (i = 0; i < 4; ++i) {
		if (_psShadowWindows.hwnds[i] && hwnd == _psShadowWindows.hwnds[i]) {
			break;
		}
	}
	if (i == 4) return DefWindowProc(hwnd, msg, wParam, lParam);

	POINT  mouse_point;
	GetCursorPos(&mouse_point);
	RECT  rec;
	GetWindowRect(hwnd, &rec);
	if(mouse_point.x<rec.left || mouse_point.x > rec.right ||
		mouse_point.y<rec.top || mouse_point.y>rec.bottom)  
		return DefWindowProc(hwnd, msg, wParam, lParam);


	switch (msg) {
	case WM_CLOSE:
		m_myApp->close();
		break;

	case WM_NCHITTEST: {
		int32 xPos = GET_X_LPARAM(lParam), yPos = GET_Y_LPARAM(lParam);
		switch (i) {
		case 0: return HTTOP;
		case 1: return (yPos < _psShadowWindows._y + _psSize) ? HTTOPRIGHT : ((yPos >= _psShadowWindows._y + _psShadowWindows._h - _psSize) ? HTBOTTOMRIGHT : HTRIGHT);
		case 2: return HTBOTTOM;
		case 3: return (yPos < _psShadowWindows._y + _psSize) ? HTTOPLEFT : ((yPos >= _psShadowWindows._y + _psShadowWindows._h - _psSize) ? HTBOTTOMLEFT : HTLEFT);
		}
		return HTTRANSPARENT;
	} break;

	case WM_NCACTIVATE: 
		DefWindowProc(hwnd, msg, wParam, lParam);
		if (m_bNCactivate) return 0;
		else {
			m_bNCactivate = true; return 1;
		}
	case WM_NCLBUTTONDOWN:
		m_bNCactivate = false;
	case WM_NCLBUTTONUP:
	case WM_NCLBUTTONDBLCLK:
	case WM_NCMBUTTONDOWN:
	case WM_NCMBUTTONUP:
	case WM_NCMBUTTONDBLCLK:
	case WM_NCRBUTTONDOWN:
	case WM_NCRBUTTONUP:
	case WM_NCRBUTTONDBLCLK:
	case WM_NCXBUTTONDOWN:
	case WM_NCXBUTTONUP:
	case WM_NCXBUTTONDBLCLK:
	case WM_NCMOUSEHOVER:
	case WM_NCMOUSEMOVE:
	case WM_NCMOUSELEAVE:
	//case WM_NCPOINTERUPDATE:
	//case WM_NCPOINTERDOWN:
	//case WM_NCPOINTERUP:
		if (wnd) {
			if (msg == WM_NCLBUTTONDOWN) {
				::SetForegroundWindow((HWND)wnd->winId());
			}
			LRESULT res = SendMessage((HWND)wnd->winId(), msg, wParam, lParam);
			return res;
		}
		return 0;
		break;
	case WM_ACTIVATE:
		if ((HWND)m_myApp && wParam == WA_ACTIVE) {
			
				::SetForegroundWindow(hwnd);
				::SetWindowPos((HWND)m_myApp->winId(), hwnd, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE);
		
		}
		return DefWindowProc(hwnd, msg, wParam, lParam);
		break;
	default:
		return DefWindowProc(hwnd, msg, wParam, lParam);
	}
	return 0;
}

調用：

//引入
#ifdef WIN32
#include "shadow_win.h"
_PsShadowWindows _psShadowWindows;
#endif

//構造
#ifdef WIN32
	_psShadowWindows.setApp(this);
	_psShadowWindows.init(QColor(0, 0, 0));
    _psShadowWindows.update(Main_Window::ShadowsChange::Hidden);
    _psShadowWindows.setResizeEnable(true);
#endif

//重載
bool CMainWindow::nativeEvent(const QByteArray & eventType, void * message, long * result)
{
	MSG *msg = static_cast<MSG *>(message);
	switch (msg->message)
	{
	case WM_PAINT:
		_psShadowWindows.update(Main_Window::ShadowsChange::Shown);
		break;
	case WM_SIZE:
		_psShadowWindows.update(Main_Window::ShadowsChange::Resized);
		break;
	case WM_MOVE:
		_psShadowWindows.update(Main_Window::ShadowsChange::Moved);
		break;
	case WM_SHOWWINDOW:
		if(!*result)
		_psShadowWindows.update(Main_Window::ShadowsChange::Hidden);
		break;
	}
	return QWidget::nativeEvent(eventType, message, result);
}

示例中用到的圖片資源：

陰影效果：