CDC(Graphical Drawing)

CDC

The CDC class defines a class of device-context objects. The CDC object provides member functions for working with a device context, such as a display or printer, as well as members for working with a display context associated with the client area of a window.

Do all drawing through the member functions of a CDC object. The class provides member functions for device-context operations, working with drawing tools, type-safe graphics device interface (GDI) object selection, and working with colors and palettes. It also provides member functions for getting and setting drawing attributes, mapping, working with the viewport, working with the window extent, converting coordinates, working with regions, clipping, drawing lines, and drawing simple shapes, ellipses, and polygons. Member functions are also provided for drawing text, working with fonts, using printer escapes, scrolling, and playing metafiles.

To use a CDC object, construct it, and then call its member functions that parallel Windows functions that use device contexts.

Note Under Windows 95, all screen coordinates are limited to 16 bits. Therefore, an int passed to a CDC member function must lie in the range –32768 to 32767.

For specific uses, the Microsoft Foundation Class Library provides several classes derived from CDC . CPaintDC encapsulates calls to BeginPaint and EndPaint. CClientDC manages a display context associated with a window’s client area. CWindowDC manages a display context associated with an entire window, including its frame and controls. CMetaFileDC associates a device context with a metafile.

CDC contains two device contexts, m_hDC and m_hAttribDC, which, on creation of a CDC object, refer to the same device. CDC directs all output GDI calls to m_hDC and most attribute GDI calls to m_hAttribDC. (An example of an attribute call is GetTextColor, while SetTextColor is an output call.)

For example, the framework uses these two device contexts to implement a CMetaFileDC object that will send output to a metafile while reading attributes from a physical device. Print preview is implemented in the framework in a similar fashion. You can also use the two device contexts in a similar way in your application-specific code.

There are times when you may need text-metric information from both the m_hDC and m_hAttribDC device contexts. The following pairs of functions provide this capability:

Uses m_hAttribDC	Uses m_hDC
GetTextExtent	GetOutputTextExtent
GetTabbedTextExtent	GetOutputTabbedTextExtent
GetTextMetrics	GetOutputTextMetrics
GetCharWidth	GetOutputCharWidth

For more information on CDC, see Device Contexts in Visual C++ Programmer's Guide.

#include <afxwin.h>

Class Members | Base Class | Hierarchy Chart

See Also CPaintDC, CWindowDC, CClientDC, CMetaFileDC 


 

CDC Class Members

Data Members
Construction/Destruction
Initialization
Device-Context Functions
Drawing-Tool Functions
Type-Safe Selection. Helpers
Color and Color Palette Functions
Drawing-Attribute Functions
Mapping Functions
Coordinate Functions
Region Functions
Clipping Functions
Line-Output Functions
Simple Drawing Functions
Ellipse and Polygon Functions
Bitmap Functions
Text Functions
Font Functions
Printer Escape Functions
Scrolling Functions
Metafile Functions
Path Functions

Data Members

m_hDC	The output-device context used by this CDC object.
m_hAttribDC	The attribute-device context used by this CDC object.

Construction

CDC	Constructs a CDC object.

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 temporary CDC object is created and attached.
DeleteTempMap	Called by the CWinApp idle-time handler to delete any temporary CDC object 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.

Coordinate Functions

DPtoHIMETRIC	Converts device units into HIMETRIC units.
DPtoLP	Converts device units into logical units.
HIMETRICtoDP	Converts HIMETRIC units into device units.
HIMETRICtoLP	Converts HIMETRIC units into logical units.
LPtoDP	Converts logical units into device units.
LPtoHIMETRIC	Converts logical units into HIMETRIC units.

Region Functions

FillRgn	Fills a specific region with the specified brush.
FrameRgn	Draws a border around a specific region using a brush.
InvertRgn	Inverts the colors in a region.
PaintRgn	Fills a region with the selected brush.

Clipping Functions

SetBoundsRect	Controls the accumulation of bounding-rectangle information for the specified device context.
GetBoundsRect	Returns the current accumulated bounding rectangle for the specified device context.
GetClipBox	Retrieves the dimensions of the tightest bounding rectangle around the current clipping boundary.
SelectClipRgn	Combines the given region with the current clipping region by using the specified mode.
ExcludeClipRect	Creates a new clipping region that consists of the existing clipping region minus the specified rectangle.
ExcludeUpdateRgn	Prevents drawing within invalid areas of a window by excluding an updated region in the window from a clipping region.
IntersectClipRect	Creates a new clipping region by forming the intersection of the current region and a rectangle.
OffsetClipRgn	Moves the clipping region of the given device.
PtVisible	Specifies whether the given point is within the clipping region.
RectVisible	Determines whether any part of the given rectangle lies within the clipping region.

Line-Output Functions

GetCurrentPosition	Retrieves the current position of the pen (in logical coordinates).
MoveTo	Moves the current position.
LineTo	Draws a line from the current position up to, but not including, a point.
Arc	Draws an elliptical arc.
ArcTo	Draws an elliptical arc. This function is similar to Arc, except that the current position is updated.
AngleArc	Draws a line segment and an arc, and moves the current position to the ending point of the arc.
GetArcDirection	Returns the current arc direction for the device context.
SetArcDirection	Sets the drawing direction to be used for arc and rectangle functions.
PolyDraw	Draws a set of line segments and Bézier splines. This function updates the current position.
Polyline	Draws a set of line segments connecting the specified points.
PolyPolyline	Draws multiple series of connected line segments. The current position is neither used nor updated by this function.
PolylineTo	Draws one or more straight lines and moves the current position to the ending point of the last line.
PolyBezier	Draws one or more Bézier splines. The current position is neither used nor updated.
PolyBezierTo	Draws one or more Bézier splines, and moves the current position to the ending point of the last Bézier spline.

Simple Drawing Functions

FillRect	Fills a given rectangle by using a specific brush.
FrameRect	Draws a border around a rectangle.
InvertRect	Inverts the contents of a rectangle.
DrawIcon	Draws an icon.
DrawDragRect	Erases and redraws a rectangle as it is dragged.
FillSolidRect	Fills a rectangle with a solid color.
Draw3dRect	Draws a three-dimensional rectangle.
DrawEdge	Draws the edges of a rectangle.
DrawFrameControl	Draw a frame control.
DrawState	Displays an image and applies a visual effect to indicate a state.

Ellipse and Polygon Functions

Chord	Draws a chord (a closed figure bounded by the intersection of an ellipse and a line segment).
DrawFocusRect	Draws a rectangle in the style used to indicate focus.
Ellipse	Draws an ellipse.
Pie	Draws a pie-shaped wedge.
Polygon	Draws a polygon consisting of two or more points (vertices) connected by lines.
PolyPolygon	Creates two or more polygons that are filled using the current polygon-filling mode. The polygons may be disjoint or they may overlap.
Polyline	Draws a polygon consisting of a set of line segments connecting specified points.
Rectangle	Draws a rectangle using the current pen and fills it using the current brush.
RoundRect	Draws a rectangle with rounded corners using the current pen and filled using the current brush.

Bitmap Functions

PatBlt	Creates a bit pattern.
BitBlt	Copies a bitmap from a specified device context.
StretchBlt	Moves a bitmap from a source rectangle and device into a destination rectangle, stretching or compressing the bitmap if necessary to fit the dimensions of the destination rectangle.
GetPixel	Retrieves the RGB color value of the pixel at the specified point.
SetPixel	Sets the pixel at the specified point to the closest approximation of the specified color.
SetPixelV	Sets the pixel at the specified coordinates to the closest approximation of the specified color. SetPixelV is faster than SetPixel because it does not need to return the color value of the point actually painted.
FloodFill	Fills an area with the current brush.
ExtFloodFill	Fills an area with the current brush. Provides more flexibility than the FloodFill member function.
MaskBlt	Combines the color data for the source and destination bitmaps using the given mask and raster operation.
PlgBlt	Performs a bit-block transfer of the bits of color data from the specified rectangle in the source device context to the specified parallelogram in the given device context.

Text Functions

TextOut	Writes a character string at a specified location using the currently selected font.
ExtTextOut	Writes a character string within a rectangular region using the currently selected font.
TabbedTextOut	Writes a character string at a specified location, expanding tabs to the values specified in an array of tab-stop positions.
DrawText	Draws formatted text in the specified rectangle.
GetTextExtent	Computes the width and height of a line of text on the attribute device context using the current font to determine the dimensions.
GetOutputTextExtent	Computes the width and height of a line of text on the output device context using the current font to determine the dimensions.
GetTabbedTextExtent	Computes the width and height of a character string on the attribute device context.
GetOutputTabbedTextExtent	Computes the width and height of a character string on the output device context.
GrayString	Draws dimmed (grayed) text at the given location.
GetTextAlign	Retrieves the text-alignment flags.
SetTextAlign	Sets the text-alignment flags.
GetTextFace	Copies the typeface name of the current font into a buffer as a null-terminated string.
GetTextMetrics	Retrieves the metrics for the current font from the attribute device context.
GetOutputTextMetrics	Retrieves the metrics for the current font from the output device context.
SetTextJustification	Adds space to the break characters in a string.
GetTextCharacterExtra	Retrieves the current setting for the amount of intercharacter spacing.
SetTextCharacterExtra	Sets the amount of intercharacter spacing.

Font Functions

GetFontData	Retrieves font metric information from a scalable font file. The information to retrieve is identified by specifying an offset into the font file and the length of the information to return.
GetKerningPairs	Retrieves the character kerning pairs for the font that is currently selected in the specified device context.
GetOutlineTextMetrics	Retrieves font metric information for TrueType fonts.
GetGlyphOutline	Retrieves the outline curve or bitmap for an outline character in the current font.
GetCharABCWidths	Retrieves the widths, in logical units, of consecutive characters in a given range from the current font.
GetCharWidth	Retrieves the fractional widths of consecutive characters in a given range from the current font.
GetOutputCharWidth	Retrieves the widths of individual characters in a consecutive group of characters from the current font using the output device context.
SetMapperFlags	Alters the algorithm that the font mapper uses when it maps logical fonts to physical fonts.
GetAspectRatioFilter	Retrieves the setting for the current aspect-ratio filter.

Printer Escape Functions

QueryAbort	Calls the AbortProc callback function for a printing application and queries whether the printing should be terminated.
Escape	Allows applications to access facilities that are not directly available from a particular device through GDI. Also allows access to Windows escape functions. Escape calls made by an application are translated and sent to the device driver.
DrawEscape	Accesses drawing capabilities of a video display that are not directly available through the graphics device interface (GDI).
StartDoc	Informs the device driver that a new print job is starting.
StartPage	Informs the device driver that a new page is starting.
EndPage	Informs the device driver that a page is ending.
SetAbortProc	Sets a programmer-supplied callback function that Windows calls if a print job must be aborted.
AbortDoc	Terminates the current print job, erasing everything the application has written to the device since the last call of the StartDoc member function.
EndDoc	Ends a print job started by the StartDoc member function.

Scrolling Functions

ScrollDC

Scrolls a rectangle of bits horizontally and vertically.

Metafile Functions

PlayMetaFile	Plays the contents of the specified metafile on the given device. The enhanced version of PlayMetaFile displays the picture stored in the given enhanced-format metafile. The metafile can be played any number of times.
AddMetaFileComment	Copies the comment from a buffer into a specified enhanced-format metafile.

Path Functions

AbortPath	Closes and discards any paths in the device context.
BeginPath	Opens a path bracket in the device context.
CloseFigure	Closes an open figure in a path.
EndPath	Closes a path bracket and selects the path defined by the bracket into the device context.
FillPath	Closes any open figures in the current path and fills the path’s interior by using the current brush and polygon-filling mode.
FlattenPath	Transforms any curves in the path selected into the current device context, and turns each curve into a sequence of lines.
GetMiterLimit	Returns the miter limit for the device context.
GetPath	Retrieves the coordinates defining the endpoints of lines and the control points of curves found in the path that is selected into the device context.
SelectClipPath	Selects the current path as a clipping region for the device context, combining the new region with any existing clipping region by using the specified mode.
SetMiterLimit	Sets the limit for the length of miter joins for the device context.
StrokeAndFillPath	Closes any open figures in a path, strikes the outline of the path by using the current pen, and fills its interior by using the current brush.
StrokePath	Renders the specified path by using the current pen.
WidenPath	Redefines the current path as the area that would be painted if the path were stroked using the pen currently selected into the device context.

CDC Overview | Base Class Members | Hierarchy Chart