Question

I am receiving a EM_CHARFORMAT message in my message handler when SetFont() is called on my custom control. But when I change the data in the CHARFORMAT structure pointed to in the LPARAM, it isn’t being used.

void CMyRichEdit::OnProtected(NMHDR* pNMHDR, LRESULT* pResult)
{
    ENPROTECTED* pEP = (ENPROTECTED*)pNMHDR;
    *pResult = 1; 

    switch(pEP->msg)
    {
    case EM_SETCHARFORMAT:
        {
        CHARFORMAT *cf = reinterpret_cast<CHARFORMAT *>(pEP->lParam);
        cf->dwEffects |= (CFE_PROTECTED | CFE_ITALIC); 
        cf->dwMask |= (CFM_PROTECTED | CFM_ITALIC);
        *pResult = 0; 
        }
        break;

The MSDN docs say only if the lParam value changes is it used over the original… but here lParam is a pointer to an object. How can I allocate a new object without the memory leaking?

Answer 1

How can I allocate a new object without the memory leaking?

I’m not sure that reallocating lParam is going to work, but since a window procedure doesn’t have to worry about being called on multiple threads, you can point lParam to a static variable safely. That way you don’t have to worry about freeing it.

case EM_SETCHARFORMAT:
    {
    static CHARFORMAT mycf;
    CHARFORMAT *cf = reinterpret_cast<CHARFORMAT *>(pEP->lParam);
    mycf = *cf;
    pEP->lParam = (LPARAM)(LONG_PTR)&mycf;
    cf->dwEffects |= (CFE_PROTECTED | CFE_ITALIC); 
    cf->dwMask |= (CFM_PROTECTED | CFM_ITALIC);
    *pResult = 0; 
    }
    break;

However, I really don’t think that this is going to solve your problem.