wpf: fixup mouse wheel events from screen coords (#7168)

I found this while crawling through conhost's WindowIo. Mouse wheel
events come in in screen coordinates, unlike literally every other mouse
event.

The WPF control was doing it wrong.

(cherry picked from commit cd72356)

src/cascadia/PublicTerminalCore/HwndTerminal.cpp

@@ -21,7 +21,7 @@ static constexpr bool _IsMouseMessage(UINT uMsg)
  return uMsg == WM_LBUTTONDOWN || uMsg == WM_LBUTTONUP || uMsg == WM_LBUTTONDBLCLK ||
  uMsg == WM_MBUTTONDOWN || uMsg == WM_MBUTTONUP || uMsg == WM_MBUTTONDBLCLK ||
  uMsg == WM_RBUTTONDOWN || uMsg == WM_RBUTTONUP || uMsg == WM_RBUTTONDBLCLK ||
- uMsg == WM_MOUSEMOVE || uMsg == WM_MOUSEWHEEL;
+ uMsg == WM_MOUSEMOVE || uMsg == WM_MOUSEWHEEL || uMsg == WM_MOUSEHWHEEL;
 }
 
 // Helper static function to ensure that all ambiguous-width glyphs are reported as narrow.
@@ -628,16 +628,21 @@ bool HwndTerminal::_CanSendVTMouseInput() const noexcept
 bool HwndTerminal::_SendMouseEvent(UINT uMsg, WPARAM wParam, LPARAM lParam) noexcept
 try
 {
- const til::point cursorPosition{
+ til::point cursorPosition{
  GET_X_LPARAM(lParam),
  GET_Y_LPARAM(lParam),
  };
 
  const til::size fontSize{ this->_actualFont.GetSize() };
  short wheelDelta{ 0 };
- if (uMsg == WM_MOUSEWHEEL)
+ if (uMsg == WM_MOUSEWHEEL || uMsg == WM_MOUSEHWHEEL)
  {
  wheelDelta = HIWORD(wParam);
+
+ // If it's a *WHEEL event, it's in screen coordinates, not window (?!)
+ POINT coordsToTransform = cursorPosition;
+ ScreenToClient(_hwnd.get(), &coordsToTransform);
+ cursorPosition = coordsToTransform;
  }
 
  return _terminal->SendMouseEvent(cursorPosition / fontSize, uMsg, getControlKeyState(), wheelDelta);