[用UpdateLayeredWindow实现任意异形窗口]
前面提到，我们可以用SetWindowRgn或SetLayeredWindowAttributes实现不规则以及半透明的效果
对于SetWindowRgn，它通过一个Rgn来设置区域，这个Rgn一般可以从图片中读取，在这张图片中，将不需要显示的区域标记为一种特殊的颜色，这里有个问题，必须保证这种颜色没有被正常的区域使用，否则会被误伤。为了解决这个问题，可以考虑用两张图片，增加一张单色的掩码图，这种方案带来了额外的管理开销。SetWindowRgn的好处是效率较高，对于大部分自绘的皮肤，一般只有四个角落有一些不规则，所以用SetWindowRgn是最好的选择。
SetLayeredWindowAttributes可以将特定的窗口设置为某种透明度，也可以用它来过滤某种颜色，匹配的颜色会变成全透明。也就是类似于SetWindowRgn的效果。SetLayeredWindowAttributes直接从DC中获得颜色，所以你需要事先绘制DC。
SetLayeredWindowAttributes过滤颜色后，相关区域虽然不可见，但是不可见的区域可以放置子窗口，这点和SetWindowRgn有所区别。此外若子窗口刷新不及时或其他原因，那么父窗口因为SetLayeredWindowAttributes被隐藏的DC颜色将被浮出水面。
UpdateLayeredWindow直接根据DC中的Alpha通道来实现透明效果，它很好的处理了和背景的Alpha Blend的问题，所以完美的解决了SetWindowRgn的锯齿问题。
Sample
template<typename T,bool DLG> class ImageFrameT{ public: BEGIN_MSG_MAP(ImageFrameT) MESSAGE_HANDLER(WM_CREATE, OnCreate) MESSAGE_HANDLER(WM_INITDIALOG, OnInitDialog) MESSAGE_HANDLER(WM_PAINT, OnPaint) MESSAGE_HANDLER(WM_ERASEBKGND, OnEraseBkgnd) MESSAGE_HANDLER(WM_LBUTTONDOWN, OnLBttonDown) END_MSG_MAP() ImageFrameT():m_res_(NULL),m_move_flag_(false){} virtual ~ImageFrameT(){} LRESULT OnCreate(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM lParam, BOOL& bHandled){ bHandled = FALSE; // 通过参数获得资源句柄 LPCREATESTRUCT lpCreateStruct = (LPCREATESTRUCT)lParam; if(lpCreateStruct && lpCreateStruct->lpCreateParams) m_res_ = (CImage*)(lpCreateStruct->lpCreateParams); ATLASSERT(m_res_); if(!DLG) this->InitSelf(); return 0; } LRESULT OnInitDialog(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM lParam, BOOL& bHandled){ bHandled = FALSE; if(lParam){ // 通过参数获得资源句柄 m_res_ = (CImage*)lParam; } if(DLG) this->InitSelf(); return 0; } LRESULT OnPaint(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/){ // OnPaint不作任何事，转到UpdateLayeredWindow处理 T* pT = static_cast<T*>(this); CPaintDC dc_(pT->m_hWnd); return TRUE; } LRESULT OnEraseBkgnd(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/){ // 屏蔽背景绘制 return TRUE; } LRESULT OnLBttonDown(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& bHandled){ // 是否支持整窗口拖动 T* pT = static_cast<T*>(this); if(this->m_move_flag_) pT->PostMessage(WM_SYSCOMMAND,0xF012,0); else bHandled = FALSE; return 0; } void SetRes(CImage* res){ // 设置资源 ATLASSERT(res); if(res) this->m_res_ = res; } void SetMoveFlag(bool flag){ // 设置是否可拖动 this->m_move_flag_ = flag; } private: void InitSelf(){ ATLASSERT(m_res_); if(m_res_){ T* pT = static_cast<T*>(this); // 设置属性WS_EX_LAYERED LONG lWindowLong = ::GetWindowLong(pT->m_hWnd, GWL_EXSTYLE) | WS_EX_LAYERED; ::SetWindowLong(pT->m_hWnd, GWL_EXSTYLE, lWindowLong); // 设置属性WS_POPUP lWindowLong = ::GetWindowLong(pT->m_hWnd, GWL_STYLE) | WS_POPUP; // 去掉一堆其他属性 lWindowLong &= ~WS_CHILD; lWindowLong &= ~WS_BORDER; lWindowLong &= ~WS_CAPTION; lWindowLong &= ~WS_SYSMENU; ::SetWindowLong(pT->m_hWnd, GWL_STYLE, lWindowLong); pT->SetWindowPos(HWND_BOTTOM,0,0, m_res_->GetWidth(),m_res_->GetHeight(), SWP_NOMOVE | SWP_NOOWNERZORDER); CClientDC dc_(pT->m_hWnd); CDC mem_dc_; mem_dc_.CreateCompatibleDC(dc_); CBitmap mem_bitmap_; mem_bitmap_.CreateCompatibleBitmap(dc_, m_res_->GetWidth(), m_res_->GetHeight()); mem_dc_.SelectBitmap(mem_bitmap_); m_res_->Draw(mem_dc_,0,0); BLENDFUNCTION pb_; pb_.AlphaFormat = 1; pb_.BlendOp = 0; pb_.BlendFlags =0; pb_.SourceConstantAlpha = 0xFF; CPoint pt_(0,0); CSize size_(m_res_->GetWidth(),m_res_->GetHeight()); ::UpdateLayeredWindow(pT->m_hWnd,dc_,&pt_,&size_,mem_dc_,&pt_,0,&pb_,ULW_ALPHA ); pT->CenterWindow(NULL); } } protected: CImage* m_res_; bool m_move_flag_; }; class CAboutDlg : public CDialogImpl<CAboutDlg>, public ImageFrameT<CAboutDlg,true> { typedef ImageFrameT<CAboutDlg,true> BaseClass; public: enum { IDD = IDD_DIALOG1 }; BEGIN_MSG_MAP(CAboutDlg) CHAIN_MSG_MAP(BaseClass) MESSAGE_HANDLER(WM_RBUTTONDOWN, OnClose) END_MSG_MAP() LRESULT OnClose(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/) { EndDialog(0); return 0; } }; CImage bitmap_bg_; BOOL ret_ = File2CImageAndImplAlpha(&bitmap_bg_,_T("res/bk.png")); ATLASSERT(ret_); CAboutDlg dlg_; dlg_.SetMoveFlag(true); dlg_.DoModal(this->m_hSubWindow_,(LPARAM)(&bitmap_bg_));放置子控件
若只需要最一个简单的窗口，那么上面的代码可以完成要求。UpdateLayeredWindow有一个问题，那就是它上面不能放置任何子窗口，放置上去的任何窗口都不可见。为了解决这个问题，一种简单的办法是自绘，在单个窗口中模拟各种消息。
若不想搞复杂，有一种变通的办法，那就是在上面放置一个非子窗口，这种子窗口大小位置保持和它一致，同时这个子窗口用SetLayeredWindowAttributes搞成全透明，接下来我们将所有子控件放到这个全透明的子窗口即可。
Sample
#define CHAIN_MSG_MAP_ALT_MEMBER_EX(theChainMember, msgMapID, msg) \ { \ if(uMsg == msg && \ theChainMember &&\ theChainMember->ProcessWindowMessage(hWnd, uMsg, wParam, lParam, lResult, msgMapID)) \ return TRUE; \ } // 放置在ImageFrameT上的子窗口 // 这个类主要处理消息的转发，通过WM_CREATE获得最顶层窗口的指针 // 并存储在m_message_变量中，然后使用CHAIN_MSG_MAP_ALT_MEMBER_EX // 将它子窗口发给它的WM_COMMAND，WM_NOTIFY转发过去 template<typename T,typename Y> class SubWindowT{ public: BEGIN_MSG_MAP(SubWindowT) MESSAGE_HANDLER(WM_CREATE, OnCreate) MESSAGE_HANDLER(WM_ERASEBKGND, OnEraseBkgnd) // 将这个不可见的窗口的WM_COMMAND和WM_NOTIFY消息 // 转发给最顶层的窗口 CHAIN_MSG_MAP_ALT_MEMBER_EX(m_message_,1,WM_COMMAND) CHAIN_MSG_MAP_ALT_MEMBER_EX(m_message_,1,WM_NOTIFY) END_MSG_MAP() SubWindowT():m_message_(NULL){}; LRESULT OnCreate(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM lParam, BOOL& bHandled){ bHandled = FALSE; T* pT = static_cast<T*>(this); LPCREATESTRUCT lpCreateStruct = (LPCREATESTRUCT)lParam; // 初始化m_message_ if(lpCreateStruct && lpCreateStruct->lpCreateParams) m_message_ = (Y*)(lpCreateStruct->lpCreateParams); ATLASSERT(m_message_); // 设置属性WS_POPUP LONG lWindowLong = ::GetWindowLong(pT->m_hWnd, GWL_STYLE) | WS_POPUP; // 去掉一堆其他属性 lWindowLong &= ~WS_CHILD; lWindowLong &= ~WS_BORDER; lWindowLong &= ~WS_CAPTION; lWindowLong &= ~WS_SYSMENU; ::SetWindowLong(pT->m_hWnd, GWL_STYLE, lWindowLong); return 0; } LRESULT OnEraseBkgnd(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/){ // 屏蔽背景消息 return TRUE; } // 这个指针指向最顶层的窗口，用它来将紧贴这顶层窗口的不可见窗口的消息 // 转发给m_message_ // 注意宏CHAIN_MSG_MAP_ALT_MEMBER_EX Y* m_message_; }; // 这个类在SubWindowT的基础上实现了全透明的效果 // 利用SetLayeredWindowAttributes可以对某种特定的颜色实现全透明过滤的特性 template<typename Y> class SubWindow1 : public CWindowImpl<SubWindow1<Y>,CWindow>, public SubWindowT<SubWindow1<Y>,Y>{ typedef SubWindowT<SubWindow1<Y>,Y> BaseClass; public: BEGIN_MSG_MAP(SubWindow1) CHAIN_MSG_MAP(BaseClass) //连接基类的消息处理逻辑，并优先处理 MESSAGE_HANDLER(WM_CREATE, OnCreate) MESSAGE_HANDLER(WM_PAINT, OnPaint) REFLECT_NOTIFICATIONS() END_MSG_MAP() LRESULT OnCreate(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM lParam, BOOL& bHandled){ bHandled = FALSE; // 设置属性WS_EX_LAYERED LONG lWindowLong = ::GetWindowLong(this->m_hWnd, GWL_EXSTYLE) | WS_EX_LAYERED; lWindowLong &= ~WS_EX_TRANSPARENT; ::SetWindowLong(this->m_hWnd, GWL_EXSTYLE, lWindowLong); // 在OnPaint里面将整个窗口刷成RGB(255,0,255) // 在这里将此颜色过滤（编程全透明） ::SetLayeredWindowAttributes(this->m_hWnd,RGB(255,0,255),0,LWA_COLORKEY); return 0; } LRESULT OnPaint(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/){ // 在OnPaint里面将整个窗口刷成RGB(255,0,255) // 以便让SetLayeredWindowAttributes过滤 CPaintDC dc_(this->m_hWnd); CRect client_rect_; this->GetClientRect(client_rect_); dc_.FillSolidRect(client_rect_,RGB(255,0,255)); return TRUE; } }; template<typename T,bool DLG,template<typename X> class SUB_WINDOW > class ImageFrameExT : public ImageFrameT<T,DLG>{ typedef ImageFrameT<T,DLG> BaseClass; public: BEGIN_MSG_MAP(ImageFrameExT) CHAIN_MSG_MAP(BaseClass) MESSAGE_HANDLER(WM_CREATE, OnCreate) MESSAGE_HANDLER(WM_INITDIALOG, OnInitDialog) MESSAGE_HANDLER(WM_MOVE, OnMove) END_MSG_MAP() ImageFrameExT(){ m_sub_rect_.SetRect(0,0,0,0); } LRESULT OnCreate(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM lParam, BOOL& bHandled){ bHandled = FALSE; T* pT = static_cast<T*>(this); if(!DLG){ // 一并创建子窗口 // 注意它将pT传给了最后一个参数，这个在 // OnCreate传给了SubWindowT m_hSubWindow_.Create(pT->m_hWnd,NULL,NULL, WS_VISIBLE,0,0U,pT); } return 0; } LRESULT OnInitDialog(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& bHandled){ bHandled = FALSE; T* pT = static_cast<T*>(this); if(DLG){ // 一并创建子窗口 // 注意这里没有WS_CHILD m_hSubWindow_.Create(pT->m_hWnd,NULL,NULL, WS_VISIBLE,0,0U,pT); } return 0; } LRESULT OnMove(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& bHandled){ // 动态更新子窗口 bHandled = FALSE; T* pT = static_cast<T*>(this); if(m_hSubWindow_.IsWindow()){ CRect win_rect_; pT->GetWindowRect(win_rect_); if(m_sub_rect_.IsRectNull()){ m_hSubWindow_.MoveWindow(win_rect_); }else{ CRect tmp_ = m_sub_rect_; tmp_.OffsetRect(win_rect_.TopLeft()); m_hSubWindow_.MoveWindow(tmp_); } } return 0; } SUB_WINDOW<T>* SubWindow(){ // 获得子窗口 return &m_hSubWindow_; } void SetSubRect(const CRect& rect){ // 可以设置让子窗口位于那块区域，而不一定要占满整屏 m_sub_rect_ = rect; } protected: SUB_WINDOW<T> m_hSubWindow_; CRect m_sub_rect_; }; class CMainFrame : public CFrameWindowImpl<CMainFrame>, public ImageFrameExT<CMainFrame,false,SubWindow1 > { typedef ImageFrameExT<CMainFrame,false,SubWindow1 > BaseClass; public: DECLARE_FRAME_WND_CLASS(NULL, IDR_MAINFRAME) BEGIN_MSG_MAP(CMainFrame) //REFLECT_NOTIFICATIONS() CHAIN_MSG_MAP(BaseClass) MESSAGE_HANDLER(WM_CREATE, OnCreate) MESSAGE_HANDLER(WM_DESTROY, OnDestroy) CHAIN_MSG_MAP(CFrameWindowImpl<CMainFrame>) ALT_MSG_MAP(1) COMMAND_CODE_HANDLER(BN_CLICKED,OnClick) END_MSG_MAP() LRESULT OnCreate(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/) { m_close_.Create(this->m_hSubWindow_, CRect(200,200,50 + 200,26 + 200), _T("Close"), WS_CHILD | WS_VISIBLE); m_help_.Create(this->m_hSubWindow_, CRect(260,200,50 + 260,26 + 200), _T("Help"), WS_CHILD | WS_VISIBLE); m_help2_.Create(this->m_hSubWindow_, CRect(320,200,50 + 320,26 + 200), _T("Help2"), WS_CHILD | WS_VISIBLE); return 0; } LRESULT OnDestroy(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& bHandled) { // 解决wtl不能关闭ws_popup的bug PostQuitMessage(0); bHandled = FALSE; return 1; } LRESULT OnClick(WORD wNotifyCode, WORD wID, HWND hWndCtl, BOOL& bHandled){ if(m_close_ == hWndCtl){ this->PostMessage(WM_CLOSE); }else if(m_help_ == hWndCtl){ }else if(m_help2_ == hWndCtl){ } return 0; } CButton m_close_; CButton m_help_; CButton m_help2_; };其他问题
若上面放置普通的矩形控件，并且不支持透明，那么啥问题都没有，然后若要实现不规则或者透明控件，那么全透明窗口被过滤的颜色将被显示出来
一个变通的办法就是将需要填充子控件的区域抠出来，并交给这个子窗口来画（这就要求放置控件区域的地方没有半透明，大部分需求都只是希望能够处理简单的异形，并且消除锯齿）。
// 将父窗口中间抠出来，交给子窗口来画 template<typename Y> class SubWindow2 : public CWindowImpl<SubWindow2<Y>,CWindow>, public SubWindowT<SubWindow2<Y>,Y>{ typedef SubWindowT<SubWindow2<Y>,Y> BaseClass; public: BEGIN_MSG_MAP(SubWindow2) CHAIN_MSG_MAP(BaseClass) MESSAGE_HANDLER(WM_PAINT, OnPaint) REFLECT_NOTIFICATIONS() END_MSG_MAP() LRESULT OnPaint(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/){ CPaintDC dc_(this->m_hWnd); ATLASSERT(m_res_); if(m_res_) m_res_->Draw(dc_,0,0); return TRUE; } inline void SetRes(CImage* res){ ATLASSERT(res); if(res) this->m_res_ = res; } private: CImage* m_res_; }; class CAboutDlgEx : public CDialogImpl<CAboutDlgEx>, public ImageFrameExT<CAboutDlgEx,true,SubWindow2> { typedef ImageFrameExT<CAboutDlgEx,true,SubWindow2> BaseClass; public: enum { IDD = IDD_DIALOG1 }; BEGIN_MSG_MAP(CAboutDlgEx) CHAIN_MSG_MAP(BaseClass) MESSAGE_HANDLER(WM_INITDIALOG, OnInitDialog) MESSAGE_HANDLER(WM_RBUTTONDOWN, OnClose) ALT_MSG_MAP(1) END_MSG_MAP() LRESULT OnInitDialog(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/){ bool ret_ = m_res_.InitFromFile( _T("res/imgbtn.png"), _T("res/imgbtn_h.png"), _T("res/imgbtn_p.png"), _T("res/imgbtn_d.png")); ATLASSERT(ret_); m_btn_.Create(this->m_hSubWindow_,NULL,NULL,0,0,0U,&m_res_); m_btn_.MoveWindow(120,120,0,0,TRUE); return 0; } LRESULT OnClose(UINT /*uMsg*/, WPARAM /*wParam*/, LPARAM /*lParam*/, BOOL& /*bHandled*/){ EndDialog(0); return 0; } ImageButton<ButtonRes,true> m_btn_; ButtonRes m_res_; };经测试，这种方案在拖动时，两个窗口交接处有明显的刷新不一致存在。
Bug
在一些非32位图像模式下，该函数会有些问题，解决办法就是强制创建32位的Bitmap
CBitmap bitmap; BITMAPINFOHEADER bmih; bmih.biSize = sizeof (BITMAPINFOHEADER) ; bmih.biWidth = 384 ; bmih.biHeight = 256 ; bmih.biPlanes = 1 ; bmih.biBitCount = 32 ; //注意32位 bmih.biCompression = BI_RGB ; bmih.biSizeImage = 0 ; bmih.biXPelsPerMeter = 0 ; bmih.biYPelsPerMeter = 0 ; bmih.biClrUsed = 0 ; bmih.biClrImportant = 0 ; bitmap.CreateDIBitmap(dc,&bmih);为了避免绘图汇到左上角，需要在调用UpdateLayeredWindow时，明确指定左上角坐标
CRect rect_; GetWindowRect(rect_); CPoint topleft(rect_.left,rect_.top); CPoint pt_(0,0); CSize size_(m_res_->GetWidth(),m_res_->GetHeight()); ::UpdateLayeredWindow(pT->m_hWnd,dc_,&topleft,&size_,mem_dc_,&pt_,0,&pb_,ULW_ALPHA );