VC++中的CDC类

在学习VC++中，CDC类是在显示数据，或者使用图形，或者使用文本中必不可少的。Windows使用与设备无关的图形设备环境(DC :Device Context) 进行显示 。MFC基础类库定义了设备环境对象类----CDC类。

CDC与CGdiObject的关系

　　说道CDC类就不能不提一下GdiObject---图形对象类。 在Windows应用程序中，设备环境与图形对象共同工作，协同完成绘图显示工作。就像画家绘画一样，设备环境好比是画家的画布，图形对象好比是画家的画笔。用画笔在画布上绘画，不同的画笔将画出不同的画来。选择合适的图形对象和绘图对象，才能按照要求完成绘图任务。

　　有关CDC类的继承

　　父类：从 CObject 直接继承而来。继承了CObject类的各种特性，如动态创建等等。

　　子类：CClientDC-------代表操作窗口的DC ，是比较常用的一个子类

　　CMetaFileDC ------响应Meta File的DC ，Meta File是一些GDI消息。

　　CPaintDC-------响应WM_PAINT消息的DC。

　　CWindowDC ------代表整个屏幕的ＤＣ

　　CDC类的数据成员

　　数据成员只有两个：

　　HDC m_hDC : CDC对象使用的输出设备上下文

　　HDC m_hAttribDC : CDC对象使用的属性设备上下文

　　二者在CDC对象创建时指向相同的设备上下文。

MSDN Library中给出的构造函数及其成员函数如下（供学习之用）：

Construction

CDC	Constructs a CDCobject.

Initialization

CreateDC	Creates a device context for a specific device.
CreateIC	Creates an information context for a specific device. This provides a fast way to get information about the device without creating a device context.
CreateCompatibleDC	Creates a memory-device context that is compatible with another device context. You can use it to prepare images in memory.
DeleteDC	Deletes the Windows device context associated with this CDC object.
FromHandle	Returns a pointer to a CDC object when given a handle to a device context. If a CDC object is not attached to the handle, a temporaryCDC object is created and attached.
DeleteTempMap	Called by the CWinApp idle-time handler to delete any temporary CDCobject created by FromHandle. Also detaches the device context.
Attach	Attaches a Windows device context to this CDC object.
Detach	Detaches the Windows device context from this CDC object.
SetAttribDC	Sets m_hAttribDC, the attribute device context.
SetOutputDC	Sets m_hDC, the output device context.
ReleaseAttribDC	Releases m_hAttribDC, the attribute device context.
ReleaseOutputDC	Releases m_hDC, the output device context.
GetCurrentBitmap	Returns a pointer to the currently selected CBitmap object.
GetCurrentBrush	Returns a pointer to the currently selected CBrush object.
GetCurrentFont	Returns a pointer to the currently selected CFont object.
GetCurrentPalette	Returns a pointer to the currently selected CPalette object.
GetCurrentPen	Returns a pointer to the currently selected CPen object.
GetWindow	Returns the window associated with the display device context.

Device-Context Functions

GetSafeHdc	Returns m_hDC, the output device context.
SaveDC	Saves the current state of the device context.
RestoreDC	Restores the device context to a previous state saved with SaveDC.
ResetDC	Updates the m_hAttribDC device context.
GetDeviceCaps	Retrieves a specified kind of device-specific information about a given display device’s capabilities.
IsPrinting	Determines whether the device context is being used for printing.

Drawing-Tool Functions

GetBrushOrg	Retrieves the origin of the current brush.
SetBrushOrg	Specifies the origin for the next brush selected into a device context.
EnumObjects	Enumerates the pens and brushes available in a device context.

Type-Safe Selection Helpers

SelectObject	Selects a GDI drawing object such as a pen.
SelectStockObject	Selects one of the predefined stock pens, brushes, or fonts provided by Windows.

Color and Color Palette Functions

GetNearestColor	Retrieves the closest logical color to a specified logical color that the given device can represent.
SelectPalette	Selects the logical palette.
RealizePalette	Maps palette entries in the current logical palette to the system palette.
UpdateColors	Updates the client area of the device context by matching the current colors in the client area to the system palette on a pixel-by-pixel basis.
GetHalftoneBrush	Retrieves a halftone brush.

Drawing-Attribute Functions

GetBkColor	Retrieves the current background color.
SetBkColor	Sets the current background color.
GetBkMode	Retrieves the background mode.
SetBkMode	Sets the background mode.
GetPolyFillMode	Retrieves the current polygon-filling mode.
SetPolyFillMode	Sets the polygon-filling mode.
GetROP2	Retrieves the current drawing mode.
SetROP2	Sets the current drawing mode.
GetStretchBltMode	Retrieves the current bitmap-stretching mode.
SetStretchBltMode	Sets the bitmap-stretching mode.
GetTextColor	Retrieves the current text color.
SetTextColor	Sets the text color.
GetColorAdjustment	Retrieves the color adjustment values for the device context.
SetColorAdjustment	Sets the color adjustment values for the device context using the specified values.

Mapping Functions

GetMapMode	Retrieves the current mapping mode.
SetMapMode	Sets the current mapping mode.
GetViewportOrg	Retrieves the x- and y-coordinates of the viewport origin.
SetViewportOrg	Sets the viewport origin.
OffsetViewportOrg	Modifies the viewport origin relative to the coordinates of the current viewport origin.
GetViewportExt	Retrieves the x- and y-extents of the viewport.
SetViewportExt	Sets the x- and y-extents of the viewport.
ScaleViewportExt	Modifies the viewport extent relative to the current values.
GetWindowOrg	Retrieves the x- and y-coordinates of the origin of the associated window.
SetWindowOrg	Sets the window origin of the device context.
OffsetWindowOrg	Modifies the window origin relative to the coordinates of the current window origin.
GetWindowExt	Retrieves the x- and y-extents of the associated window.
SetWindowExt	Sets the x- and y-extents of the associated window.
ScaleWindowExt	Modifies the window extents relative to the current values.

等。。。

http://blog.sina.com.cn/s/blog_4bc179a80100cuda.html