OpenEuphoria

Re: Win32 Font Metrics

• Posted by Daniel Berstein <daber at PAIR.COM> Feb 25, 1999
• 495 views

At 08:16 PM 25-02-1999 , you wrote:
>Has anyone got Win32 code that returns the width of font characters?
>
>I've written a routine (included at the end of this note), but I'm not sure
>what the problem with it is... The values returned from the function are
>suspicious, and I suspect that I in addition I have to scale the values by
>converting logical units to physical units.
>
>In the Win95 book, Petzold leaves this out. He "cheats" by using the average
>character size. I need the character metrics so I can calculate the length
>of a string, and be able to display justified text.
>
>Even a pointer to some C or VB code that does this would be a great help.
>
>Thanks.

Take a look to GetTextExtentPoint32 in gdi32.dll it may be the answer :)

Syntax:

BOOL GetTextExtentPoint32(
        HDC  DC,
        LPCTSTR  Str,
        int  Count,
        LPSIZE  Size
        );

Description:

This function retrieves the width and height of the string pointed by the
Str parameter, in logical units. The width and height are based on the
attributes of the string currently selected into the device context
identified by the DC parameter. The clipping region of the specified device
context does not affect the computed dimensions. In instances where a
string containing kerning pairs is output to a device supporting character
kerning, the dimernsions returned by this function may not match the sum of
the individual character dimensions in the string.


Parameters:

DC: A handle to the device context whose currently selected font is used to
determine the string's width and height.

Str: A pointer to a string whose width and height are to be retrieved. This
does not have to be a null-terminated string, as the Count parameter
specifies the string length.

Count: Specifies the number of characters in the string pointed to by the
Str parameter.

Size: A pointer to a SIZE structure that recieves the width and height of
the specified string based on the attributes of the font selected into the
specified device context.

Return value:

If the function succeeds, it return TRUE; otherwise it returns FALSE. To
get extended error information, call the GetLastError function.

The SIZE structure is as follows:

typedef struct tagSIZE {
        LONG cx;
        LONG cy;
} SIZE;

The SIZE structure specifies the width and height of a rectangle.

cx: Specifies the rectangle's width.
cy: Specifies the rectangle's height.


Here is an untested attemp (I assume your GDI functions, never have looked
at them):

[please wait for the beep... beeeep!]

global constant xGetTextExtentPoint32 =
        linkFunc(gdi32,  "GetTextExtentPoint32", -- Maybe need 'A' extension?
          {C_POINTER, C_POINTER, C_INT, C_POINTER}, C_INT )

global function getFontTextSize( integer id, sequence str )
        sequence size
        atom hdc, pstr, psize

        size = {0,0}

        -- Allocate LPSTRZ
        pstr = allocate_string(str)
        if not pstr then
                warnErr( "allocate_string in getFontTextSize failed." )
                return size
        end if

        -- Allocate SIZE structure
        psize = allocate(8)
        if not psize then
                warnErr( "allocate in getFontTextSize failed." )
                free(pstr)
                return size
        end if

        -- get the device context
        hdc = getDC( id )

        -- set the font
        putFontIntoHDC( hdc, id )

        -- Get text dimensions
if not c_func( xGetTextExtentPoint32, { hdc, pstr, length(str), psize }
        )
then
                warnErr( "GetTextExtentPoint32 in getFontTextSize failed." )
                size = peek4s({psize, 2})
        end if

        -- Cleanup
        replaceObject( hdc, DefaultFontID, ForProgram )
        releaseDC( id )
        free( psize )
        free( pstr )

        -- Return {cx,cy} sequence
        return size

end function

[tut, tut, tut...]

The returned dimensions are in logical units. Use the LPtoDP API function
to convert them to device units.

Hope this helps.


Regards,
         Daniel  Berstein
         [daber at pair.com]