System Pens and System Brushes

System pens and system brushes are pens and brushes that are used to create system colors. In this section we will discuss how to create and use system pens and brushes.

There are two ways to create system pens and brushes. First, you can create pens and brushes using the SystemColors class. SystemColors represents the system colors in GDI+, providing static properties for system colors, such as ActiveBorder and ControlText. The second way to create system pens and brushes uses the SystemPens and SystemBrushes classes.

For performance reasons, it is a good idea to use the SystemPens and SystemBrushes classes rather than creating pens and brushes by using the SystemColors class.

4.5.1 System Pens

The SystemPens class represents a pen created with the system colors. This class has a static property for each system color that represents the system pen with that particular color. Table 4.16 lists the properties of the SystemPens class.

The SystemPens class also provides a methodFromSystemColorthat creates a Pen object from a Color structure. To create a system pen, we pass a SystemColors object. The following code shows how to use the FromSystemColor method:

Table 4.16. SystemPens properties

Property	Description
ActiveCaptionText	Pen with active window's title bar color
Control	Pen with control color
ControlDark	Pen with the shadow color of a 3D element.
ControlDarkDark	Pen with the dark shadow color of a 3D element.
ControlLight	Pen with the light color of a 3D element.
ControlLightLight	Pen with the highlight color of a 3D element.
ControlText	Pen with the control text color
GrayText	Pen with disabled color
Highlight	Pen with highlighting
HighlightText	Pen with highlighted text color
InactiveCaptionText	Pen with inactive title bar color
InfoText	Pen with the color of the text of a ToolTip
MenuText	Pen with the color of a menu's text
WindowFrame	Pen with the color of a window frame
WindowText	Pen with the color of the text in the client area of a window

Pen pn = SystemPens.FromSystemColor(
 SystemColors.HotTrack);

4.5.2 System Brushes

The SystemBrushes class represents a Brush object using the system colors. All properties of SystemBrushes are static read-only properties. Table 4.17 describes these properties.

Table 4.17. SystemBrushes properties

Property	Description
ActiveBorder	Brush object with the color of the active window's border
ActiveCaption	Brush object with the background color of the active window's title bar
ActiveCaptionText	Brush object with the color of the text in the active window's title bar
AppWorkspace	Brush object with the color of the application workspace
Control	Brush object with the face color of a 3D element
ControlDark	Brush object with the shadow color of a 3D element
ControlDarkDark	Brush object with the dark shadow color of a 3D element
ControlLight	Brush object with the light color of a 3D element
ControlLightLight	Brush object with the highlight color of a 3D element
ControlText	Brush object with the color of text in a 3D element
Desktop	Brush object with the color of the desktop
Highlight	Brush object with the color of the background of selected items
HighlightText	Brush object with the color of the text of selected items
HotTrack	Brush object with the color used to designate a hot-tracked item
InactiveBorder	Brush object with the color of an inactive window's border
InactiveCaption	Brush object with the color of the background of an inactive window's title bar
Info	Brush object with the color of the background of a ToolTip
Menu	Brush object with the color of a menu's background
ScrollBar	Brush object with the color of the background of a scroll bar
Window	Brush object with the color of the background in the client area of a window
WindowText	Brush object with the color of the text in the client area of a window

Note

The MSDN documentation states that the SystemBrushes properties return a SolidBrush object, but that statement is not quite accurate. These properties return a Brush object that must be cast to a SolidBrush object. If you run the code without casting them, the compiler throws an error.

The SystemBrushes class also provides a FromSystemColor method, which creates a Brush object from a specified system color. The following code shows how to use the FromSystemColor method:

SolidBrush brush =
 (SolidBrush)SystemBrushes.FromSystemColor
 (SystemColors.ActiveCaption);

Disposing of System Pens and Brushes

You cannot dispose of system pens and brushes. If you try to dispose of them, GDI+ generates an error because these objects belong to the system.

Listing 4.26 uses SystemBrushes and SystemPens objects to draw two lines and a rectangle.

Listing 4.26 Using the SystemBrushes and SystemPens classes

private void Form1_Paint(object sender,
 System.Windows.Forms.PaintEventArgs e)
{
 Graphics g = e.Graphics;
 // Create a pen using SystemPens
 Pen pn = SystemPens.FromSystemColor(
 SystemColors.HotTrack);
 // Create a brush using SystemBrushes
 SolidBrush brush =
 (SolidBrush)SystemBrushes.FromSystemColor
 (SystemColors.ActiveCaption);
 // Draw lines and rectangles
 g.DrawLine(pn, 20, 20, 20, 100);
 g.DrawLine(pn, 20, 20, 100, 20);
 g.FillRectangle(brush, 30, 30, 50, 50);
 // YOU CAN'T DISPOSE OF SYSTEM PENS AND
 // BRUSHES. IF YOU TRY, GDI+ WILL GENERATE
 // AN ERROR.
 //pn.Dispose();
 //brush.Dispose();
}

Figure 4.31 shows the output from Listing 4.26.

Figure 4.31. Using system pens and system brushes