Re: get font from HDC

From:
mosfet <john.doe@anonymous.org>
Newsgroups:
microsoft.public.vc.mfc
Date:
Mon, 20 Aug 2007 15:41:06 +0200
Message-ID:
<46c999f2$0$426$426a34cc@news.free.fr>
Finally I did this :

hfontBase = (HFONT)::GetCurrentObject(hdc, OBJ_FONT);
if (hfontBase == NULL){
    hfontBase = (HFONT) GetStockObject(SYSTEM_FONT) );
}
SelectObject(hdc, hfontBase);

mosfet a ?crit :

Actually I want to use the following control
http://www.codeproject.com/listctrl/html_listctrl.asp (on Smartphone but
that's not the question) that is a Custom CListCtrl deriving from CWnd.
It's appropriate because on smartphone you don't have much space and
this listctrl allow to have a different size for each row in addtion to
support a few HTML tags.

But when reading the code I saw that it uses hfontBase =
(HFONT)SelectObject(hdc, (HFONT)GetStockObject(SYSTEM_FONT)); and I
think it would be better to use the font selected in the control.
For instanc I could do a SetFont on my listctrl and the DrawHTML
function should use it to do its rendering (bold, italic, ...)

About savedc and restordc it's because I haven't posted all the code.

int __stdcall DrawHTML(
                       HDC hdc, // handle of device context
                       LPCTSTR lpString, // address of string to draw
                       int nCount, // string length, in characters
                       LPRECT lpRect, // address of structure with
formatting dimensions
                       UINT uFormat // text-drawing flags
                       )
{
    LPCTSTR Start;
    int Left, Top, MaxWidth, MinWidth, Height;
    int SavedDC;
    int Tag, TokenLength;
    HFONT hfontBase, hfontSpecial[FV_NUMBER];
    int Styles, CurStyles;
    SIZE size;
    int Index, LineHeight;
    POINT CurPos;
    int WidthOfSPace, XPos;
    BOOL WhiteSpace;
    RECT rc;
    
    if (hdc == NULL || lpString == NULL)
        return 0;
    if (nCount < 0)
        nCount = _tcslen(lpString);
    
    if (lpRect != NULL) {
        Left = lpRect->left;
        Top = lpRect->top;
        MaxWidth = lpRect->right - lpRect->left;
    } else {
        GetCurrentPositionEx(hdc, &CurPos);
        Left = CurPos.x;
        Top = CurPos.y;
        MaxWidth = GetDeviceCaps(hdc, HORZRES) - Left;
    } /* if */
    if (MaxWidth < 0)
        MaxWidth = 0;
    
    /* toggle flags we do not support */
    uFormat &= ~(DT_CENTER | DT_RIGHT | DT_TABSTOP);
    uFormat |= (DT_LEFT | DT_NOPREFIX);
    
    /* get the "default" font from the DC */
    SavedDC = SaveDC(hdc);
    hfontBase = ::GetCurrentObject(hdc, OBJ_FONT);
    hfontBase = (HFONT)SelectObject(hdc,
(HFONT)GetStockObject(SYSTEM_FONT));
    SelectObject(hdc, hfontBase);
    /* clear the other fonts, they are created "on demand" */
    for (Index = 0; Index < FV_NUMBER; Index++)
        hfontSpecial[Index] = NULL;
    hfontSpecial[0] = hfontBase;
    Styles = 0; /* assume the active font is normal weight, roman,
non-underlined */
    
                /* get font height (use characters with ascender and
descender);
                * we make the assumption here that changing the font
style will
                * not change the font height
    */
    GetTextExtentPoint32(hdc, _T("?y"), 2, &size);
    LineHeight = size.cy;
    
    /* run through the string, word for word */
    XPos = 0;
    MinWidth = 0;
    stacktop = 0;
    CurStyles = -1; /* force a select of the proper style */
    Height = 0;
    WhiteSpace = FALSE;
    
    Start = lpString;
    for ( ;; ) {
        Tag = GetToken(&Start, &nCount, &TokenLength, &WhiteSpace);
        if (Tag < 0)
            break;
        switch (Tag & ~ENDFLAG) {
        case tP:
            if ((Tag & ENDFLAG) == 0 && (uFormat & DT_SINGLELINE) == 0) {
                if (Start != lpString)
                    Height += 3 * LineHeight / 2;
                XPos = 0;
            } /* if */
            break;
        case tBR:
            if ((Tag & ENDFLAG) == 0 && (uFormat & DT_SINGLELINE) == 0) {
                Height += LineHeight;
                XPos = 0;
            } /* if */
            break;
        case tB:
            Styles = (Tag & ENDFLAG) ? Styles & ~FV_BOLD : Styles |
FV_BOLD;
            break;
        case tI:
            Styles = (Tag & ENDFLAG) ? Styles & ~FV_ITALIC : Styles |
FV_ITALIC;
            break;
        case tU:
            Styles = (Tag & ENDFLAG) ? Styles & ~FV_UNDERLINE : Styles |
FV_UNDERLINE;
            break;
        case tSUB:
            Styles = (Tag & ENDFLAG) ? Styles & ~FV_SUBSCRIPT : Styles |
FV_SUBSCRIPT;
            break;
        case tSUP:
            Styles = (Tag & ENDFLAG) ? Styles & ~FV_SUPERSCRIPT : Styles
| FV_SUPERSCRIPT;
            break;
        case tFONT:
            if ((Tag & ENDFLAG) == 0) {
                if (_tcsnicmp(Start + 6, _T("color="), 6) == 0)
                    PushColor(hdc, ParseColor(Start + 12));
            } else {
                PopColor(hdc);
            } /* if */
            break;
        default:
            if (Tag == (tNONE | ENDFLAG))
                break;
            if (CurStyles != Styles) {
                if (hfontSpecial[Styles] == NULL)
                    hfontSpecial[Styles] = GetFontVariant(hdc,
hfontBase, Styles);
                CurStyles = Styles;
                SelectObject(hdc, hfontSpecial[Styles]);
                /* get the width of a space character (for word spacing) */
                GetTextExtentPoint32(hdc, _T(" "), 1, &size);
                WidthOfSPace = size.cx;
            } /* if */
            /* check word length, check whether to wrap around */
            GetTextExtentPoint32(hdc, Start, TokenLength, &size);
            if (size.cx > MaxWidth)
                MaxWidth = size.cx; /* must increase width: long
non-breakable word */
            if (WhiteSpace)
                XPos += WidthOfSPace;
            if (XPos + size.cx > MaxWidth && WhiteSpace) {
                if ((uFormat & DT_WORDBREAK) != 0) {
                    /* word wrap */
                    Height += LineHeight;
                    XPos = 0;
                } else {
                    /* no word wrap, must increase the width */
                    MaxWidth = XPos + size.cx;
                } /* if */
            } /* if */
            /* output text (unless DT_CALCRECT is set) */
            if ((uFormat & DT_CALCRECT) == 0) {
                /* handle negative heights, too (suggestion of "Sims") */
                /*if (Top < 0)
                {
                    SetRect(&rc, Left + XPos, Top - Height,
                    Left + MaxWidth, Top - (Height + LineHeight));
                }
                else*/
                {
                    SetRect(&rc, Left + XPos, Top + Height,
                    Left + MaxWidth, Top + Height + LineHeight);
                }
               
                /* reposition subscript text to align below the baseline */
                DrawText(hdc, Start, TokenLength, &rc,
                    uFormat | ((Styles & FV_SUBSCRIPT) ? DT_BOTTOM |
DT_SINGLELINE : 0));
               
                    /* for the underline style, the spaces between words
should be
                    * underlined as well
                */
                if (WhiteSpace && (Styles & FV_UNDERLINE) && XPos >=
WidthOfSPace)
                {
                    if (Top < 0)
                    {
                        SetRect(&rc, Left + XPos - WidthOfSPace, Top -
Height,
                            Left + XPos, Top - (Height + LineHeight));
                    }
                    else
                    {
                        SetRect(&rc, Left + XPos - WidthOfSPace, Top +
Height,
                            Left + XPos, Top + Height + LineHeight);
                    }
                    DrawText(hdc, _T(" "), 1, &rc, uFormat);
                } /* if */
            } /* if */
            /* update current position */
            XPos += size.cx;
            if (XPos > MinWidth)
                MinWidth = XPos;
            WhiteSpace = FALSE;
    } /* if */
    
    Start += TokenLength;
  } /* for */

  RestoreDC(hdc, SavedDC);
  for (Index = 1; Index < FV_NUMBER; Index++) /* do not erase
hfontSpecial[0] */
      if (hfontSpecial[Index] != NULL)
          DeleteObject(hfontSpecial[Index]);
    
      /* store width and height back into the lpRect structure */
      if ((uFormat & DT_CALCRECT) != 0 && lpRect!=NULL) {
          lpRect->right = lpRect->left + MinWidth;
          if (lpRect->top < 0)
              lpRect->bottom = lpRect->top - (Height + LineHeight);
          else
              lpRect->bottom = lpRect->top + Height + LineHeight;
      } /* if */
    
      return Height;
}

Joseph M. Newcomer a ?crit :

On Mon, 20 Aug 2007 15:05:43 +0200, mosfet <john.doe@anonymous.org>
wrote:

Hi,

I would like to modify a function used to render some HTML and use
the font I have choosen :

// C functions
int __stdcall DrawHTML(
                       HDC hdc, // handle of device context
                       LPCTSTR lpString, // address of string to draw
                       int nCount, // string length, in
characters
                       LPRECT lpRect, // address of structure
with formatting dimensions
                       UINT uFormat // text-drawing flags
                       )
{
...

/* get the "default" font from the DC */
    SavedDC = SaveDC(hdc);

****
You do a SaveDC but not a RestoreDC? ****

    hfontBase = (HFONT)SelectObject(hdc,
(HFONT)GetStockObject(SYSTEM_FONT));
    SelectObject(hdc, hfontBase);

****
It would be easier to write
    hfontBase = ::GetCurrentObject(hdc, OBJ_FONT);
and not worry about the SelectObject pair
****

    /* clear the other fonts, they are created "on demand" */
    for (Index = 0; Index < FV_NUMBER; Index++)
        hfontSpecial[Index] = NULL;
    hfontSpecial[0] = hfontBase;

****
Note that if, in between times, the font which is currently selected
into the DC is
deleted, the old handle you have saved here will become meaningless.
Therefore, you
cannot rely on the fact that this handle will still be valid at the
time you use it.
Better to do an array of LOGFONT values, rather than an array of HFONTs.
****

...
}

Here is my code :

void CxListCtrl::DrawItem(CDC *pDC, CRect rcItem, HTMLLIST_ITEM
*pItem, BOOL bSelected)
{

 CFont* pOldFont = MemDC.SelectObject( &m_font );

DrawHTML(pDC->GetSafeHdc(),pItem->sItemText,pItem->sItemText.GetLength(),

            &rc,DT_LEFT|DT_WORDBREAK);

****
So why do you save the font in the MemDC when you don't actually use
it? Note that the
m_font handle must represent a valid font to be selected, but the line
seems to have no
meaning as shown in this function. I would also suggest something like
    HDC dc = pDC->GetSafeHdc();
    if(dc == NULL)
        return;
               DrawHTML(dc, ...as above...);

}

My problem is I don't know how to modify DrawHTML to take the font
specified in DrawItem because from what I understand DrawHTML is
using a default font :

hfontBase = (HFONT)SelectObject(hdc,
(HFONT)GetStockObject(SYSTEM_FONT));
    SelectObject(hdc, hfontBase);


****
I don't see the relationship of the above code to the problem. Where
is this line of
code? I also could not find any method called DrawHTML in the MSDN
documentation, could
you say more about where it is implemented or what it is supposed to do?
                    joe
****

Joseph M. Newcomer [MVP]
email: newcomer@flounder.com
Web: http://www.flounder.com
MVP Tips: http://www.flounder.com/mvp_tips.htm

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