Highlight inactive darken tab on mouse hover

Fix #15791, close #15794

PowerEditor/src/WinControls/TabBar/TabBar.cpp

@@ -1476,6 +1476,12 @@ void TabBarPlus::drawItem(DRAWITEMSTRUCT* pDrawItemStruct, bool isDarkMode)
 			brushColour = colorActiveBg;
 		}
 		
+		if (_currentHoverTabItem == nTab && brushColour != colorActiveBg) // hover on a "darker" inactive tab
+		{
+			HLSColour hls(brushColour);
+			brushColour = hls.toRGB4DarkModWithTuning(15, 0); // make it lighter slightly
+		}
+		
 		hBrush = ::CreateSolidBrush(brushColour);
 		::FillRect(hDC, &inactiveRect, hBrush);
 		::DeleteObject(static_cast<HGDIOBJ>(hBrush));