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 );