Fix floating panels position resetting in multimon extended mode

This fixes a regression caused by PR #15236 (Fix for the "lost" panels problem).

As the Virtual Screen in the extended multi-monitor mode can start not a the point 0,0 (as the primary monitor does) but also at some negative coordinates, we have to deal with it.

The MS Virtual Screen concept ref:
 https://learn.microsoft.com/en-us/windows/win32/gdi/the-virtual-screen

Fix #15498 , fix #16077, close #16079

PowerEditor/src/MISC/Common/Common.cpp

@@ -13,6 +13,7 @@
 //
 // You should have received a copy of the GNU General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
+#include <windows.h>
 #include <algorithm>
 #include <stdexcept>
 #include <shlwapi.h>
@@ -1903,3 +1904,56 @@ bool doesPathExist(const wchar_t* path, DWORD milliSec2wait, bool* isTimeoutReac
 	getFileAttributesExWithTimeout(path, &attributes, milliSec2wait, isTimeoutReached);
 	return (attributes.dwFileAttributes != INVALID_FILE_ATTRIBUTES);
 }
+
+#if defined(__GNUC__)
+#define LAMBDA_STDCALL __attribute__((__stdcall__))
+#else
+#define LAMBDA_STDCALL 
+#endif
+
+// check if the window rectangle intersects with any currently active monitor's working area
+// (this func handles also possible extended monitors mode aka the MS Virtual Screen)
+bool isWindowVisibleOnAnyMonitor(const RECT& rectWndIn)
+{
+	struct Param4InOut
+	{
+		const RECT& rectWndIn;
+		bool isWndVisibleOut = false;
+	};
+
+	// callback func to check for intersection with each existing monitor
+	auto callback = []([[maybe_unused]] HMONITOR hMon, [[maybe_unused]] HDC hdc, LPRECT lprcMon, LPARAM lpInOut) -> BOOL LAMBDA_STDCALL
+	{
+		Param4InOut* paramInOut = reinterpret_cast<Param4InOut*>(lpInOut);
+		RECT rectIntersection{};
+		if (::IntersectRect(&rectIntersection, &(paramInOut->rectWndIn), lprcMon))
+		{
+			paramInOut->isWndVisibleOut = true; // the window is at least partially visible on this monitor
+			return FALSE; // ok, stop the enumeration
+		}
+		return TRUE; // continue enumeration as no intersection yet
+	};
+
+	// get scaled Virtual Screen size (scaled coordinates are saved by the Notepad++ into config.xml)
+	// - for unscaled, one has to 1st set the SetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE_V2) & then use GetSystemMetricsForDpi with 96
+	// - for getting the VS RECT, we cannot use here the SystemParametersInfo with SPI_GETWORKAREA!
+	//   (while the SPI_SETWORKAREA is working with the VS coordinates the SPI_GETWORKAREA not...)
+	RECT rectVirtualScreen{ ::GetSystemMetrics(SM_XVIRTUALSCREEN), ::GetSystemMetrics(SM_YVIRTUALSCREEN),
+		::GetSystemMetrics(SM_CXVIRTUALSCREEN), ::GetSystemMetrics(SM_CYVIRTUALSCREEN) }; 
+
+	// 1) Before checking for intersections with individual monitors, we verify if the window's rectangle
+	//    is within the MS Virtual Screen area. If it is outside, this func exits with false early,
+	//    as the window in question cannot be visible on any individual monitor present.
+	RECT rectIntersection{};
+	if (!::IntersectRect(&rectIntersection, &rectWndIn, &rectVirtualScreen))
+	{
+		// the window in question is completely outside the overall Virtual Screen bounds
+		return false;
+	}
+
+	// 2) Using the EnumDisplayMonitors WINAPI to check each present monitor's visible area, we ensure that we are only looking
+	//    at monitors that are part of the Virtual Screen but not at Virtual Space coordinates where is NOT a monitor present.
+	Param4InOut param4InOut{ rectWndIn, false };
+	::EnumDisplayMonitors(NULL, &rectVirtualScreen, callback, reinterpret_cast<LPARAM>(&param4InOut));
+	return param4InOut.isWndVisibleOut;
+}

PowerEditor/src/MISC/Common/Common.h

@@ -288,3 +288,7 @@ BOOL getFileAttributesExWithTimeout(const wchar_t* filePath, WIN32_FILE_ATTRIBUT
 bool doesFileExist(const wchar_t* filePath, DWORD milliSec2wait = 0, bool* isTimeoutReached = nullptr);
 bool doesDirectoryExist(const wchar_t* dirPath, DWORD milliSec2wait = 0, bool* isTimeoutReached = nullptr);
 bool doesPathExist(const wchar_t* path, DWORD milliSec2wait = 0, bool* isTimeoutReached = nullptr);
+
+
+// check if the window rectangle intersects with any currently active monitor's working area
+bool isWindowVisibleOnAnyMonitor(const RECT& rectWndIn);

PowerEditor/src/Parameters.cpp

@@ -6910,40 +6910,32 @@ void NppParameters::feedDockingManager(TiXmlNode *node)
 			int w = FWI_PANEL_WH_DEFAULT;
 			int h = FWI_PANEL_WH_DEFAULT;
 
+			bool bInputDataOk = false;
 			if (floatElement->Attribute(L"x", &x))
 			{
-				if ((x > (maxMonitorSize.cx - 1)) || (x < 0))
-					x = 0; // invalid, reset
-			}
 				if (floatElement->Attribute(L"y", &y))
 				{
-				if ((y > (maxMonitorSize.cy - 1)) || (y < 0))
-					y = 0; // invalid, reset
-			}
 					if (floatElement->Attribute(L"width", &w))
 					{
-				if (w > maxMonitorSize.cx)
-				{
-					w = maxMonitorSize.cx; // invalid, reset
-				}
-				else
-				{
-					if (w < _nppGUI._dockingData._minFloatingPanelSize.cx)
-						w = _nppGUI._dockingData._minFloatingPanelSize.cx; // invalid, reset
-				}
-			}
 						if (floatElement->Attribute(L"height", &h))
 						{
-				if (h > maxMonitorSize.cy)
+							RECT rect{ x,y,w,h };
+							bInputDataOk = isWindowVisibleOnAnyMonitor(rect);
+						}
+					}
+				}
+			}
+
+			if (!bInputDataOk)
 			{
-					h = maxMonitorSize.cy; // invalid, reset
-				}
-				else
-				{
-					if (h < _nppGUI._dockingData._minFloatingPanelSize.cy)
-						h = _nppGUI._dockingData._minFloatingPanelSize.cy; // invalid, reset
-				}
+				// reset to adjusted factory defaults
+				// (and the panel will automatically be on the current primary monitor due to the x,y == 0,0)
+				x = 0;
+				y = 0;
+				w = _nppGUI._dockingData._minFloatingPanelSize.cx;
+				h = _nppGUI._dockingData._minFloatingPanelSize.cy + FWI_PANEL_WH_DEFAULT;
 			}
+
 			_nppGUI._dockingData._floatingWindowInfo.push_back(FloatingWindowInfo(cont, x, y, w, h));
 		}
 	}