How to get window position of other program when the program is in expand monitor? - winapi

Question

I want to detect whether a program is full screen in the expand monitor. I have got the expand monitor position using EnumDisplayMonitors. So if I get the program's position, I can compare it with expand monitor's position and get the result.
So I get the HWND of the program, and then I use ::GetWindowRect(HWND, &rect); But the rect is not correct.
HWND g_HWND = NULL;
BOOL CALLBACK EnumWindowsProcMy(HWND hwnd, LPARAM lParam)
{
DWORD lpdwProcessId;
GetWindowThreadProcessId(hwnd, &lpdwProcessId);
if (lpdwProcessId == lParam)
{
g_HWND = hwnd;
return FALSE;
}
return TRUE;
}
DWORD GetProcessidFromName(CString strName)
{
PROCESSENTRY32 pe;
DWORD id = 0;
HANDLE hSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
pe.dwSize = sizeof(PROCESSENTRY32);
if (!Process32First(hSnapshot, &pe))
{
return 0;
}
pe.dwSize = sizeof(PROCESSENTRY32);
while (Process32Next(hSnapshot, &pe) != FALSE)
{
CString strTmp = pe.szExeFile;
if (strName.CompareNoCase(strTmp) == 0)
{
id = pe.th32ProcessID;
break;
}
}
CloseHandle(hSnapshot);
return id;
}
CRect rect[2] = { (0,0,0,0),(0,0,0,0) }; //rect[1] stores the expand monitor's position
BOOL CALLBACK Monitorenumproc(HMONITOR hMonitor, HDC hdcMonitor, LPRECT lprcMonitor, LPARAM dwData)
{
static BOOL first = FALSE;
MONITORINFO monitorinfo;
monitorinfo.cbSize = sizeof(MONITORINFO);
GetMonitorInfo(hMonitor, &monitorinfo);
if (monitorinfo.dwFlags == MONITORINFOF_PRIMARY)
{
if (!first)
{
first = TRUE;
rect[0] = monitorinfo.rcMonitor;
return TRUE;
}
else
{
first = FALSE;
return FALSE;
}
}
else
{
rect[1] = monitorinfo.rcMonitor;
}
return TRUE;
}
...
//get the position of xxx.exe
EnumDisplayMonitors(NULL, NULL, Monitorenumproc, 0);
EnumWindows(EnumWindowsProcMy, GetProcessidFromName(_T("xxx.exe")));
RECT rect1;
::GetWindowRect(g_HWND, &rect1); //rect1 is not correct!

Answer 1

I'm not sure what exactly you mean by
But the rect is not correct.
but here is what I see may seem incorrect:
Negative values, which indicate the window position relative to the primary display. You have to do the [right-left, bottom-top] calculation to get the size.
Values larger than the display size which means the rect includes the area occupied by the drop shadow.
See the documentation of GetWindowRect
In Windows Vista and later, the Window Rect now includes the area
occupied by the drop shadow.
Calling GetWindowRect will have different behavior depending on
whether the window has ever been shown or not. If the window has not
been shown before, GetWindowRect will not include the area of the drop
shadow.
To get the window bounds excluding the drop shadow, use
DwmGetWindowAttribute, specifying DWMWA_EXTENDED_FRAME_BOUNDS. Note
that unlike the Window Rect, the DWM Extended Frame Bounds are not
adjusted for DPI. Getting the extended frame bounds can only be done
after the window has been shown at least once.
So use the snippet below to get the size without the drop shadow:
RECT dwmExtFrameBounds;
DwmGetWindowAttribute(g_HWND, DWMWINDOWATTRIBUTE::DWMWA_EXTENDED_FRAME_BOUNDS, &dwmExtFrameBounds, sizeof(RECT));
Bonus read: Why does a maximized window have the wrong window rectangle?