新版的QQ在截圖時(shí)加入了窗口自動(dòng)識別的功能，能根據鼠標的位置自動(dòng)畫(huà)出下面窗口的輪廓。今天有人在論壇上問(wèn)起這個(gè)問(wèn)題，下面我們來(lái)探討這個(gè)功能的實(shí)現原理。
首先我們要明白截圖軟件的基本原理，截圖時(shí)實(shí)際上是新建了一個(gè)全屏窗口，然后將當前桌面的截圖畫(huà)在上面，大部分截圖軟件，包括QQ都是這么做的。根據鼠標位置獲取下層窗口，有好幾個(gè)類(lèi)似的API可以用(WindowFromPoint, ChildWindowFromPoint, ChildWindowFromPointEx,RealChildWindowFromPoint)。
這里我們重點(diǎn)關(guān)注ChildWindowFromPointEx，因為我們知道截圖時(shí)有個(gè)全屏窗口覆蓋在上面，通過(guò)鼠標位置去取得窗口，肯定首先取到的是這個(gè)全屏窗口，所以我們要把這個(gè)窗口過(guò)濾掉，而只有ChildWindowFromPointEx這個(gè)API有窗口過(guò)濾功能。
class CSCWinFilter
{
public:
static BOOL IsFilterWindow(HWND hWnd)
{
_ASSERTE(hWnd != NULL);
DWORD dwProcessID = GetCurrentProcessId();
if(hWnd != NULL && IsWindow(hWnd))
{
DWORD dwWinProcessId(0);
GetWindowThreadProcessId(hWnd, &dwWinProcessId);
if(dwProcessID == dwWinProcessId)
{
return TRUE;
}
}
return FALSE;
}
static DWORD GetIncludeStyle()
{
return WS_VISIBLE;
}
static DWORD GetExcludeStyleEx()
{
return WS_EX_TRANSPARENT;
}
static BOOL IsTargetPopupWindow()
{
return FALSE;
}
};
class CSCWinInfo
{
public:
HWND m_hWnd;
CRect m_rtWin; //window rect
INT m_nLevel; // 1 - pop up window ; 2
N - child window
};
//pop up win 1 (level 1)
.. first Z order
// child11 (level 2)
// child12 (level 2)
// chilld121 (level 3)
// chilld122 (level 3)
//
// child3 (level 2)
//pop up win2
// child21 (level 2)
// child21 (level 2)
//
.
//
.
//pop up winN
. last Z order
template<typename CWinFilterTraits = CSCWinFilter>
class CSCWinSpy: public CHYSingleton<CSCWinSpy>
{
public:
BOOL SnapshotAllWinRect()
{
ClearData();
// cache current window Z order when call this function
EnumWindows(EnumWindowsSnapshotProc, 1);
return TRUE;
}
//get from current Z order of desktop
HWND GetHWNDByPoint(CPoint pt)
{
m_hWndTarget = NULL;
EnumWindows(EnumWindowsRealTimeProc, MAKELPARAM(pt.x, pt.y));
return m_hWndTarget;
}
CRect GetWinRectByPoint(CPoint ptHit, BOOL bGetInRealTime = FALSE)
{
CRect rtRect(0, 0, 0, 0);
if(bGetInRealTime) //get from current Z order
{
HWND hWndTarget = GetHWNDByPoint(ptHit);
if(hWndTarget != NULL )
{
GetWindowRect(hWndTarget, &rtRect);
}
}
else //get from snapshot cache
{
GetRectByPointFromSnapshot(ptHit, rtRect);
}
return rtRect;
}
protected:
static BOOL CALLBACK EnumWindowsRealTimeProc(HWND hwnd, LPARAM lParam)
{
if(!PtInWinRect(hwnd, CPoint(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam)))) return TRUE;
if(ShouldWinBeFiltered(hwnd)) return TRUE;
m_hWndTarget = hwnd;
if(CWinFilterTraits::IsTargetPopupWindow()) return FALSE; //this is the target window, exit search
EnumChildWindows(hwnd, EnumChildRealTimeProc, lParam);
return FALSE;
}
static BOOL CALLBACK EnumChildRealTimeProc(HWND hwnd, LPARAM lParam)
{
if(!PtInWinRect(hwnd, CPoint(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam)))) return TRUE;
if(ShouldWinBeFiltered(hwnd)) return TRUE;
m_hWndTarget = hwnd;
EnumChildWindows(hwnd, EnumChildRealTimeProc, lParam);
return FALSE;
}
protected:
static BOOL CALLBACK EnumWindowsSnapshotProc(HWND hwnd, LPARAM lParam)
{
INT nLevel = lParam;
if(ShouldWinBeFiltered(hwnd)) return TRUE;
SaveSnapshotWindow(hwnd, nLevel);
if(!CWinFilterTraits::IsTargetPopupWindow())
{
++nLevel;
EnumChildWindows(hwnd, EnumChildSnapshotProc, nLevel);
}
return TRUE;
}
static BOOL CALLBACK EnumChildSnapshotProc(HWND hwnd, LPARAM lParam)
{
INT nLevel = lParam;
if(ShouldWinBeFiltered(hwnd)) return TRUE;
SaveSnapshotWindow(hwnd, nLevel);
++nLevel;
EnumChildWindows(hwnd, EnumChildSnapshotProc, nLevel);
return TRUE;
}
protected:
static BOOL PtInWinRect(HWND hWnd, CPoint pt)
{
CRect rtWin(0, 0, 0, 0);
GetWindowRect(hWnd, &rtWin);
return PtInRect(&rtWin, pt);
}
static BOOL ShouldWinBeFiltered(HWND hWnd)
{
if(CWinFilterTraits::IsFilterWindow(hWnd)) return TRUE;
DWORD dwStyle = GetWindowLong(hWnd, GWL_STYLE);
DWORD dwStyleMust = CWinFilterTraits::GetIncludeStyle();
if((dwStyle & dwStyleMust) != dwStyleMust) return TRUE;
DWORD dwStyleEx = GetWindowLong(hWnd, GWL_EXSTYLE);
DWORD dwStyleMustNot = CWinFilterTraits::GetExcludeStyleEx();
if((dwStyleMustNot & dwStyleEx) != 0) return TRUE;
return FALSE;
}
//find the first window that level is biggest
static BOOL GetRectByPointFromSnapshot(CPoint ptHit, CRect& rtRet)
{
int nCount = m_arSnapshot.size();
_ASSERTE(nCount > 0);
CSCWinInfo* pInfo = NULL;
CSCWinInfo* pTarget = NULL;
for(int i=0; i<nCount; ++i)
{
pInfo = m_arSnapshot[i];
_ASSERTE(pInfo != NULL);
//target window is found
//and level is not increasing,
//that is checking its sibling or parent window, exit search
if(pTarget != NULL
&& pInfo->m_nLevel <= pTarget->m_nLevel)
{
break;
}
if(PtInRect(&pInfo->m_rtWin, ptHit))
{
if(pTarget == NULL)
{
pTarget = pInfo;
}
else
{
if( pInfo->m_nLevel > pTarget->m_nLevel)
{
pTarget = pInfo;
}
}
}
}
if(pTarget != NULL)
{
#ifdef _DEBUG
if(pTarget != NULL)
{
HWND hWnd = pTarget->m_hWnd;
TCHAR szText[128] = {0};
_sntprintf(szText, 127, _T("GetRectByPointFromSnapshot: pt(%d, %d), hWnd(%x)"),
ptHit.x, ptHit.y, (UINT)(pInfo->m_hWnd));
OutputDebugString(szText);
}
#endif
rtRet.CopyRect(&pTarget->m_rtWin);
return TRUE;
}
return FALSE;
}
static VOID SaveSnapshotWindow(HWND hWnd, INT nLevel)
{
_ASSERTE(hWnd != NULL && IsWindow(hWnd));
CRect rtWin(0, 0, 0, 0);
GetWindowRect(hWnd, &rtWin);
if(rtWin.IsRectEmpty()) return;
CSCWinInfo* pInfo = new CSCWinInfo;
if(pInfo == NULL) return;
pInfo->m_hWnd = hWnd;
pInfo->m_nLevel = nLevel;
pInfo->m_rtWin = rtWin;
m_arSnapshot.push_back(pInfo);
}
static VOID ClearData()
{
int nCount = m_arSnapshot.size();
for(int i=0; i<nCount; ++i)
{
delete m_arSnapshot[i];
}
m_arSnapshot.clear();
}
protected:
friend class CHYSingleton<CSCWinSpy>;
CSCWinSpy() { NULL; }
~CSCWinSpy() { ClearData(); }
static HWND m_hWndTarget;
static std::vector<CSCWinInfo*> m_arSnapshot;
};
template<typename T> HWND CSCWinSpy<T>::m_hWndTarget = NULL;
template<typename T> std::vector<CSCWinInfo*> CSCWinSpy<T>::m_arSnapshot;
CRect rtSelect = CSCWinSpy<CSCWinFilter>::GetInstance()->GetWinRectByPoint(pt, FALSE);
