Remove menubar white line under dark mode

Fix #9984, close #9985

PowerEditor/src/NppBigSwitch.cpp

@@ -161,7 +161,22 @@ LRESULT Notepad_plus::process(HWND hwnd, UINT message, WPARAM wParam, LPARAM lPa
 		{
 			// Note: lParam is -1 to prevent endless loops of calls
 			::SendMessage(_dockingManager.getHSelf(), WM_NCACTIVATE, wParam, -1);
-			return ::DefWindowProc(hwnd, message, wParam, lParam);
+			result = ::DefWindowProc(hwnd, message, wParam, lParam);
+			if (NppDarkMode::isDarkMenuEnabled() && NppDarkMode::isEnabled())
+			{
+				NppDarkMode::drawUAHMenuNCBottomLine(hwnd);
+			}
+			return result;
+		}
+
+		case WM_NCPAINT:
+		{
+			result = ::DefWindowProc(hwnd, message, wParam, lParam);
+			if (NppDarkMode::isDarkMenuEnabled() && NppDarkMode::isEnabled())
+			{
+				NppDarkMode::drawUAHMenuNCBottomLine(hwnd);
+			}
+			return result;
 		}
 
 		case WM_ERASEBKGND:

PowerEditor/src/NppDarkMode.cpp

@@ -353,6 +353,34 @@ namespace NppDarkMode
 		}
 	}
 
+	void drawUAHMenuNCBottomLine(HWND hWnd)
+	{
+		MENUBARINFO mbi = { sizeof(mbi) };
+		if (!GetMenuBarInfo(hWnd, OBJID_MENU, 0, &mbi))
+		{
+			return;
+		}
+
+		RECT rcClient = { 0 };
+		GetClientRect(hWnd, &rcClient);
+		MapWindowPoints(hWnd, nullptr, (POINT*)&rcClient, 2);
+
+		RECT rcWindow = { 0 };
+		GetWindowRect(hWnd, &rcWindow);
+
+		OffsetRect(&rcClient, -rcWindow.left, -rcWindow.top);
+
+		// the rcBar is offset by the window rect
+		RECT rcAnnoyingLine = rcClient;
+		rcAnnoyingLine.bottom = rcAnnoyingLine.top;
+		rcAnnoyingLine.top--;
+
+
+		HDC hdc = GetWindowDC(hWnd);
+		FillRect(hdc, &rcAnnoyingLine, NppDarkMode::getDarkerBackgroundBrush());
+		ReleaseDC(hWnd, hdc);
+	}
+
 	// from DarkMode.h
 
 	void initExperimentalDarkMode(bool fixDarkScrollbar, bool dark)

PowerEditor/src/NppDarkMode.h

@@ -55,6 +55,7 @@ namespace NppDarkMode
 	// processes messages related to UAH / custom menubar drawing.
 	// return true if handled, false to continue with normal processing in your wndproc
 	bool runUAHWndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam, LRESULT* lr);
+	void drawUAHMenuNCBottomLine(HWND hWnd);
 
 	// from DarkMode.h
 	void initExperimentalDarkMode(bool fixDarkScrollbar, bool dark);