Windows API: Guess the next caret position - c++

Question

I'm currently writing a function to get the current line/column of an EDIT control, and I'm stuck on a problem:
If I use WM_KEYUP to handle the caret position, the coordinates are valid but it can't be updated every "frame" since it waits for the user to release the pressed key
If I use WM_KEYDOWN, GetCaretPos returns the "previous" position of the caret (well, it's an obvious issue since it hasn't moved yet.)
Is there anything I can do to guess the next position of a caret? is it efficient if I just use EM_GETSEL?
LRESULT Edit::HandleMessage(UINT msg, WPARAM wParam, LPARAM lParam)
{
switch (msg)
{
case WM_LBUTTONDOWN:
{
// Get character position from the mouse cursor's position (currently, there's no conversion of the coordinates if the mouse cursor is out of bound)
POINT pntMousePos{ 0 };
pntMousePos.x = GET_X_LPARAM(lParam);
pntMousePos.y = GET_Y_LPARAM(lParam);
LRESULT notifyValue = this->Notify(EM_CHARFROMPOS, 0, MAKELPARAM(pntMousePos.x, pntMousePos.y));
int lineIdx = static_cast<int>(this->Notify<int, LPARAM>(EM_LINEINDEX, -1));
if (lineIdx == NULL) {
DWORD beg, end;
lineIdx = Notify(EM_GETSEL, &beg, &end);
}
m_caretPos.line = HIWORD(notifyValue) + 1;
m_caretPos.column = (LOWORD(notifyValue) - lineIdx) + 1;
// Send a custom message to the main window
SendMessage(GetParent(m_parent) /*The EDIT control is actually a child of a tab control that is itself a child of the main window, ignore this */, CEM_GETLINEINFO, MAKEWPARAM(m_caretPos.line, m_caretPos.column), 0);
}
break;
case WM_KEYDOWN:
{
// Get Character position from the carret's position
// Get text metric (doesn't work so I removed some lines)
TEXTMETRIC tm{0};
HDC hdc = GetDC(m_self);
SelectObject(hdc, this->m_fnt);
GetTextMetricsW(hdc, &tm);
ReleaseDC(m_self, hdc);
POINT caretPos{ 0 };
GetCaretPos(&caretPos);
LRESULT notifyValue = this->Notify(EM_CHARFROMPOS, 0, MAKELPARAM(caretPos.x, caretPos.y));
int lineIdx = static_cast<int>(this->Notify<int, LPARAM>(EM_LINEINDEX, -1));
m_caretPos.line = HIWORD(notifyValue) + 1;
m_caretPos.column = (LOWORD(notifyValue) - lineIdx) + 1;
SendMessage(GetParent(m_parent), CEM_GETLINEINFO, MAKEWPARAM(m_caretPos.line, m_caretPos.column), 0);
}
break;
}
return DefSubclassProc(m_self, msg, wParam, lParam);
}