Visual Basic.NET How to Program (PDF)

Chapter 16 Graphics and Multimedia 697
Programmers can define precise information about a font’s metrics (or properties), such
as height, descent (the amount that characters dip below the baseline), ascent (the amount
that characters rise above the baseline) and leading (the difference between the ascent of one
line and the decent of the previous line). Figure 16.10 illustrates these properties.
Class FontFamily defines characteristics common to a group of related fonts. Class
FontFamily provides several methods used to determine the font metrics that are shared
by members of a particular family. These methods are summarized in Fig. 16.11.
The program shown in Fig. 16.12 calls method ToString to display the metrics of
two fonts. Line 21 creates Font arial and sets it to 12-point Arial font. Line 22 uses
class Font property FontFamily to obtain object arial’s FontFamily object. Lines
30–31 call ToString to output the String representation of the font. Lines 33–47 then
use methods of class FontFamily to return integers specifying the ascent, descent, height
and leading of the font. Lines 50–67 repeat this process for font sansSerif, a Font
object derived from the MS Sans Serif FontFamily.
height xy1Õ
Fig. 16.10 An illustration of font metrics.
Method Description
GetCellAscent Returns an Integer representing the ascent of a font as measured
in design units.
GetCellDescent Returns an Integer representing the descent of a font as measured
in design units.
GetEmHeight Returns an Integer representing the height of a font as measured
in design points.
GetLineSpacing Returns an Integer representing the distance between two consecutive
lines of text as measured in design units.
Fig. 16.11 FontFamily methods that return font-metrics information.
1 ' Fig. 16.12: UsingFontMetrics.vb
2 ' Displaying font metric information.
3
4 Imports System
5 Imports System.Drawing
6 Imports System.Drawing.Text
leading
ascent
baseline
descent
Fig. 16.12 FontFamily class used to obtain font-metric information (part 1 of 3).