This article has been
excerpted from book "Graphics Programming with GDI+".
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 systems pens and brushes
use 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.
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 method FormSystemColor that 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:
Pen pn =
SystemPens.FromSystemColor(SystemColors.HotTrack);
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 |
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 active window's title bar |
|
AppWorkspace |
Brush object with
the color of the application work space |
|
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 title bar |
|
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 the 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 FromSystemMethod:
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,
GDIF+ generates an error because these objects belong to the system
Listing 4.26 uses SystemBrushes and SystemPens object to draw two lines and
rectangle.
Listing 4.26: Using the SystemBrushes and SystemPens classes
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
SystemPensSystemBrushes
{
public partial
class Form1 :
Form
{
public Form1()
{
InitializeComponent();
}
private void
Form1_Paint(object sender,
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
Conclusion
Hope the article would have helped you in understanding how to draw a line chart
in GDI+. Read other articles on GDI+ on the website.
![bookGDI.jpg]()
|
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. |