Get fontsize base on text width?

Question

Hi,
Suppose I have a CString L"Marks sample" with fixed width = 81(points),
How do I determine its font size?
Assume the font name is Arial and ignore the formatting conditions like bold..

I'm using the GetTextExtentPoint32 function, but it seems to be applying the opposite condition.

Thanks you!.

Answer 1

If you want to fit the text into some width, then maybe try several font sizes. For example, the next loop starts with 6-point font and increases it until the width is achieved:

CString text = L"Marks sample";
CString font_name = L"Arial";
int required_width_points = 81;
float font_size_points;


CClientDC dc( this );
dc.SetMapMode( MM_TWIPS );
int required_width_twips = required_width_points * 20;

for( font_size_points = 6.0;; font_size_points += 0.1 )
{
   CFont font;
   font.CreatePointFont( font_size_points * 10, font_name, &dc );

   CFont* old_font = dc.SelectObject( &font );
   CRect r( 0, 0, 0, 0 );
   dc.DrawText( text, r, DT_LEFT | DT_TOP | DT_SINGLELINE | DT_NOCLIP | DT_NOPREFIX | DT_CALCRECT );
   dc.SelectObject( old_font );

   if( r.Width( ) == required_width_twips ) break;

   if( r.Width( ) > required_width_twips )
   {
      font_size_points -= 0.1;
      break;
   }
}

This is the current window (a CWnd*). The result is in font_size_points.

You can also consider a binary search algorithm.

Answer 2

You can calculate the font size from the height, not the width :

INFO: Calculating The Logical Height and Point Size of a Font