Font in .NET in context of GDI classes

This article has been excerpted from book "Graphics Programming with GDI+".

Typography Namespace

In the .NET framework library, two namespaces define the font-related functionality: System.Drawing and System.Drawing.Text .The System.Drawing namespace contains general typography functionality, and System.Drawing.Text contains advanced typography functionality. Before using any of the typography-related classes in your application, you must include the appropriate namespace. We will discuss advanced typography in section 5.6. 

The font class provides functionality for fonts, including methods and properties to define functionalities such as font style, size, name, and conversions. Before we discuss the Font class, we will introduce the FontStyle enumeration and the FontFamily class, which we will use to create Font objects.

The FontStyle Enumeration

The FontStyle enumeration defines the common style of a font. The member of FontStyle are described in Table 5.4

The FontFamily Class 

The FontFamily class provides methods and properties to work with font families. Table 5.5 describes the properties of the FontFamily class.

TABLE 5.4 FontStyle members

Member	Description
Bold	Bold text
Italic	Italic text
Regular	Normal text
Strikeout	Text with a line through the middle
Underline	Underlined text

TABLE 5.5: FontFamily Properties

Property	Description
Families	Returns an array of all the font families associated with the current graphics context.
GenericMonospace	Returns a monospace font family
GenericSansSerif	Returns a sans serif font family
GenericSerif	Returns a serif font family
Name	Returns the name of a font family

Table 5.6 describes the methods of the FontFamily class. 

Table 5.6 introduces some new terms, including base line, ascent, and descent. Let's see what they mean. Figure 5.10 shows a typical font in windows. As you can see, although the letters b and q are the same size, their starting points and ending points (top and bottom locations) are different. The total height of a font-including ascent, descent, and extra space-is called the line spacing. Ascent is the height above the base line, and decent is the height below the base line. As figure 5.10 shows, two characters may have different positions along the base line. For some fonts, the extra value is 0, but others it is not.

For some fonts, line spacing is some of the ascent and descent. Listing 5.6 create a new fonts uses get the values of line spacing, ascent, and descent and, calculates the extra space by subtracting ascent and descent from the line space. The following list identifies the get methods of a FontFamily object:

• GetCellAscent returns the cell ascent, in font design units.
• GetCellDescent returns the cell descent, in font design units.
• GetCelEmHeight returns the em height, in font design units.
• GetLineSpacing returns the line spacing for font family

Figure 5.10: Font metrics

In addition to these get methods, the Font object class provides GetHeight, which returns the height of a Font object.

As Listing 5.6, shows, we use GetLineSpacing, GetLineAscent, GetLineDescent, and GetEmHeight to get line spacing, ascent, descent and font height, respectively, and than we display the output in massage box.

TABLE 5.6 FontFamily methods

Method	Description
GetCellAscent	Returns the cell ascent, in font design units of a font family.
GetCellDescent	Returns the cell descent, in font design units of a font family.
GetEmHeight	Returns the height, in font design units of the em square for the specified style.
GetFamilies	Returns an array that contains all font families available for a graphics object. This method takes an argument of Graphics type.
GetLineSpacing	Returns the amount of space between two consecutive lines of text for a font family.
GetName	Return the name, in the specified language, of a font family.
IsStyleAvialable	Before applying a style to a font, you may want to know whether the font family in question supports that style. This method returns true if a font style is available. For example, the following code snippet checks whether or not the Arial font family supports italics: FontFamily ff =new FontFamily ('Arial"); if (ff.IsStyleAvailable(FontStyle.Italic))            //do something

LISTING 5.6 Getting line spacing, ascending, descending and fontheight

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

namespace WindowsFormsApplication1

{

     public partial class Form1 : Form

    {

        public Form1()

        {

             InitializeComponent();

        }

        private void Form1_Paint(object sender, PaintEventArgs e)

        {

             //Create a Graphocs object 

            Graphics g = this.CreateGraphics();

             //Create a font object

            Font fnt = new Font("Verdana", 10);

             //Get height

            float lnSpace = fnt.GetHeight(g);

             //Get line spacing

            int cellSpace = fnt.FontFamily.GetLineSpacing(fnt.Style);

             //get cell ascent

            int cellAscent = fnt.FontFamily.GetCellAscent(fnt.Style);

             //Get cell descent

            int cellDescent = fnt.FontFamily.GetCellDescent(fnt.Style);

             //Get font height

            int emHeight = fnt.FontFamily.GetEmHeight(fnt.Style);

             //Get free space

            float free = cellSpace - (cellAscent + cellDescent);

             //Display values

            string str = " Cell Height :" + lnSpace.ToString() + ", Line Spacing: " + cellSpace.ToString() + " Ascent : " +

             cellAscent.ToString() + " Decent :" +

             cellDescent.ToString() + ",Free:" + free.ToString() +

            " EM Height:" + emHeight.ToString();

            MessageBox.Show(str.ToString());

             //Dispose of objects

            fnt.Dispose();

            g.Dispose();

        }

    }

}

Figure 5.11 shows the output from Listing 5.6 we get cell height, line spacing, ascent, descent, free (extra) space, and em height.

The GraphicsUnit Enumeration 

You can define the unit of measure of a font when you construct a Font object. The Font class constructor takes an argument of type GraphicsUnit enumeration, which specifies the unit of measure of a font. The default unit of measure for fonts is the point (1/72 inch) .you can get the current unit of a font by using the unit property of the font class .The following code snippet returns the current unit of the font:

            Font fnt = new Font(" Verdana", 10);

            MessageBox.Show(fnt.Unit.ToString());

The members of the GraphicsUnit enumeration are described in Table 5.7

FIGURE 5.11 Getting line spacing, ascent, descent free (extra) space, and height of a font

TABLE 5.7 GraphicsUnit members

Member	Unit of Measure
Display	1/75 inch
Document	1/300 inch
Inch	1 inch
Millimeter	1 Millimeter
Pixel	1 pixel
Point	1/72 inch
World	The world unit

Conclusion

Hope the article would have helped you in understanding Font in .NET in context of GDI classes. Read other articles on GDI+ on the website.

This book teaches .NET developers how to work with GDI+ as they develop applications that include graphics, or that interact with monitors or printers. It begins by explaining the difference between GDI and GDI+, and covering the basic concepts of graphics programming in Windows.