Debugging font linking - c++

Question

I have a problem with a program we're developing. It is written using MFC but does not use unicode. We have made a translation into simplified chinese. So far this is our first and only localization. We have moved all strings to resources to make them translateable. Everything seems to work fine on our computers (both Win7 and XP) but for some customers computers running windows XP we get problems:
On those computers all translated strings work except for those we enter into tree cotrols (CTreeCtrl is used directly). I'm not sure if it is the tree control or the text we enter that causes the problem, but the font seems to not get substituted in those controls. My guess is that maybe it does not get substituted because some of the strings also contain latin characters. Still, that kind of substitution seems to work in other places of the program and not all strings entered into the tree contain those characters either.
So my first question is: Is there a way to get to know what is happening inside the control? We can have remote access to the computers where the problem is happening but running a debugger on them may be a little tricky. What kind of tools can be used to diagnose this problem?
One possible solution that crossed my mind was to subclass the tree controls to get more control over the actual text drawing, maybe using the approach from http://blogs.msdn.com/b/oldnewthing/archive/2004/07/16/185261.aspx to get around the problem. Could this be effective or would it just be an awful lot of work for nothing?
Thanks a lot!

Answer 1

Ok, it seems on their system there was either a bug in the tree control implementation or they had some systemwide addin that hooked into the drawing in some way. What I ended up doing was to do custom drawing through notifications in the tree view and then using font linking to resolve the fonts. I dont think font linking would be necessary, though, because I think most of the time it ended up doing just TextOutW() with the preselected font anyway.
Here is a somewhat simplified code sample of what I ended up with:
void MyDlg::OnCustomDrawTreeItem( NMHDR* pNMHDR, LRESULT* pResult )
{
if (!mpFontLink)
{
*pResult = CDRF_DODEFAULT;
return;
}
LPNMTVCUSTOMDRAW pCustomdraw = (LPNMTVCUSTOMDRAW) pNMHDR;
switch(pCustomdraw->nmcd.dwDrawStage)
{
case CDDS_PREPAINT:
{
// Ask to do custom draw
*pResult = CDRF_NOTIFYITEMDRAW;
break;
}
case CDDS_ITEMPREPAINT:
{
// Ask for post paint notification
*pResult = CDRF_NOTIFYPOSTPAINT;
break;
}
case CDDS_ITEMPOSTPAINT:
{
// Get the rect of only the item, not the tree stuff
RECT rcItem;
m_pageTree.GetItemRect((HTREEITEM) pCustomdraw->nmcd.dwItemSpec, &rcItem, TRUE);
// Erase the item background in case the previous string drawn was wider
HDC hDC = pCustomdraw->nmcd.hdc;
FillRect( hDC, &rcItem, (HBRUSH) GetClassLongPtr(m_pageTree.GetSafeHwnd(), GCLP_HBRBACKGROUND));
pageStruct *pS = (pageStruct*) pCustomdraw->nmcd.lItemlParam;
DWORD dwFontCodepages = 0, dwStrCodepages = 0;
HFONT hOriginalFont = (HFONT)GetCurrentObject(hDC, OBJ_FONT);
HRESULT hr = mpFontLink->GetFontCodePages( hDC, hOriginalFont, &dwFontCodepages);
OML_CStringW tData = pS->csCaption.GetBuffer();
// Set up position etc
DWORD dwAlignOrig = GetTextAlign(hDC);
if (!(dwAlignOrig & TA_UPDATECP)) {
SetTextAlign(hDC, dwAlignOrig | TA_UPDATECP);
}
POINT ptOrig;
MoveToEx(hDC, 2 + rcItem.left, 1 + rcItem.top, &ptOrig);
SetTextColor( hDC, pCustomdraw->clrText );
SetBkColor( hDC, pCustomdraw->clrTextBk );
// Loop over the parts of the text
TuInt32 nIndex = 1;
while (nIndex <= tData.GetLength())
{
long nActualChars = 0;
wchar_t *pStr = (wchar_t*)tData.BaseGetItemP( nIndex );
TuInt32 nChars = 1 + tData.GetLength() - nIndex;
hr = mpFontLink->GetStrCodePages(pStr, nChars,
dwFontCodepages, &dwStrCodepages, &nActualChars);
if (dwStrCodepages & dwFontCodepages)
{
// We end up here almost every time, that is why TextOutW would probably be enough.
// This part is supported by the original font (or the GDI can help us switch automatically)
TextOutW(hDC, 0, 0, pStr, nActualChars);
}
else
{
// We need to link
HFONT hLinked;
if (FAILED(hr = mpFontLink->MapFont(hDC, dwStrCodepages, 0, &hLinked)))
{
// Fail: Output the rest without linking
TextOutW( hDC, 0, 0, pStr, nChars );
break;
}
// Output with linked font
SelectObject(hDC, hLinked);
TextOutW( hDC, 0, 0, pStr, nActualChars);
SelectObject(hDC, hOriginalFont);
mpFontLink->ReleaseFont( hOriginalFont );
}
nIndex += nActualChars;
}
OML_LOG_1( "_END:");
// Reset alignment mode
if (!(dwAlignOrig & TA_UPDATECP)) {
SetTextAlign(hDC, dwAlignOrig);
MoveToEx(hDC, ptOrig.x, ptOrig.y, NULL);
}
*pResult = CDRF_SKIPDEFAULT;
}
default:
{
*pResult = CDRF_DODEFAULT;
break;
}
}
} /* OnCustomDrawTreeItem */