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CDC Class

Defines a class of device-context objects.

class CDC : public CObject

Members

Public Constructors

Name

Description

CDC::CDC

Constructs a CDC object.

Public Methods

Name

Description

CDC::AbortDoc

Terminates the current print job, erasing everything the application has written to the device since the last call of the StartDoc member function.

CDC::AbortPath

Closes and discards any paths in the device context.

CDC::AddMetaFileComment

Copies the comment from a buffer into a specified enhanced-format metafile.

CDC::AlphaBlend

Displays bitmaps that have transparent or semitransparent pixels.

CDC::AngleArc

Draws a line segment and an arc, and moves the current position to the ending point of the arc.

CDC::Arc

Draws an elliptical arc.

CDC::ArcTo

Draws an elliptical arc. This function is similar to Arc, except that the current position is updated.

CDC::Attach

Attaches a Windows device context to this CDC object.

CDC::BeginPath

Opens a path bracket in the device context.

CDC::BitBlt

Copies a bitmap from a specified device context.

CDC::Chord

Draws a chord (a closed figure bounded by the intersection of an ellipse and a line segment).

CDC::CloseFigure

Closes an open figure in a path.

CDC::CreateCompatibleDC

Creates a memory-device context that is compatible with another device context. You can use it to prepare images in memory.

CDC::CreateDC

Creates a device context for a specific device.

CDC::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.

CDC::DeleteDC

Deletes the Windows device context associated with this CDC object.

CDC::DeleteTempMap

Called by the CWinApp idle-time handler to delete any temporary CDC object created by FromHandle. Also detaches the device context.

CDC::Detach

Detaches the Windows device context from this CDC object.

CDC::DPtoHIMETRIC

Converts device units into HIMETRIC units.

CDC::DPtoLP

Converts device units into logical units.

CDC::Draw3dRect

Draws a three-dimensional rectangle.

CDC::DrawDragRect

Erases and redraws a rectangle as it is dragged.

CDC::DrawEdge

Draws the edges of a rectangle.

CDC::DrawEscape

Accesses drawing capabilities of a video display that are not directly available through the graphics device interface (GDI).

CDC::DrawFocusRect

Draws a rectangle in the style used to indicate focus.

CDC::DrawFrameControl

Draw a frame control.

CDC::DrawIcon

Draws an icon.

CDC::DrawState

Displays an image and applies a visual effect to indicate a state.

CDC::DrawText

Draws formatted text in the specified rectangle.

CDC::DrawTextEx

Draws formatted text in the specified rectangle using additional formats.

CDC::Ellipse

Draws an ellipse.

CDC::EndDoc

Ends a print job started by the StartDoc member function.

CDC::EndPage

Informs the device driver that a page is ending.

CDC::EndPath

Closes a path bracket and selects the path defined by the bracket into the device context.

CDC::EnumObjects

Enumerates the pens and brushes available in a device context.

CDC::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.

CDC::ExcludeClipRect

Creates a new clipping region that consists of the existing clipping region minus the specified rectangle.

CDC::ExcludeUpdateRgn

Prevents drawing within invalid areas of a window by excluding an updated region in the window from a clipping region.

CDC::ExtFloodFill

Fills an area with the current brush. Provides more flexibility than the CDC::FloodFill member function.

CDC::ExtTextOut

Writes a character string within a rectangular region using the currently selected font.

CDC::FillPath

Closes any open figures in the current path and fills the path's interior by using the current brush and polygon-filling mode.

CDC::FillRect

Fills a given rectangle by using a specific brush.

CDC::FillRgn

Fills a specific region with the specified brush.

CDC::FillSolidRect

Fills a rectangle with a solid color.

CDC::FlattenPath

Transforms any curves in the path selected into the current device context, and turns each curve into a sequence of lines.

CDC::FloodFill

Fills an area with the current brush.

CDC::FrameRect

Draws a border around a rectangle.

CDC::FrameRgn

Draws a border around a specific region using a brush.

CDC::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.

CDC::GetArcDirection

Returns the current arc direction for the device context.

CDC::GetAspectRatioFilter

Retrieves the setting for the current aspect-ratio filter.

CDC::GetBkColor

Retrieves the current background color.

CDC::GetBkMode

Retrieves the background mode.

CDC::GetBoundsRect

Returns the current accumulated bounding rectangle for the specified device context.

CDC::GetBrushOrg

Retrieves the origin of the current brush.

CDC::GetCharABCWidths

Retrieves the widths, in logical units, of consecutive characters in a given range from the current font.

CDC::GetCharABCWidthsI

Retrieves the widths, in logical units, of consecutive glyph indices in a specified range from the current TrueType font.

CDC::GetCharacterPlacement

Retrieves various types of information on a character string.

CDC::GetCharWidth

Retrieves the fractional widths of consecutive characters in a given range from the current font.

CDC::GetCharWidthI

Retrieves the widths, in logical coordinates, of consecutive glyph indices in a specified range from the current font.

CDC::GetClipBox

Retrieves the dimensions of the tightest bounding rectangle around the current clipping boundary.

CDC::GetColorAdjustment

Retrieves the color adjustment values for the device context.

CDC::GetCurrentBitmap

Returns a pointer to the currently selected CBitmap object.

CDC::GetCurrentBrush

Returns a pointer to the currently selected CBrush object.

CDC::GetCurrentFont

Returns a pointer to the currently selected CFont object.

CDC::GetCurrentPalette

Returns a pointer to the currently selected CPalette object.

CDC::GetCurrentPen

Returns a pointer to the currently selected CPen object.

CDC::GetCurrentPosition

Retrieves the current position of the pen (in logical coordinates).

CDC::GetDCBrushColor

Retrieves the current brush color.

CDC::GetDCPenColor

Retrieves the current pen color.

CDC::GetDeviceCaps

Retrieves a specified kind of device-specific information about a given display device's capabilities.

CDC::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.

CDC::GetFontLanguageInfo

Returns information about the currently selected font for the specified display context.

CDC::GetGlyphOutline

Retrieves the outline curve or bitmap for an outline character in the current font.

CDC::GetGraphicsMode

Retrieves the current graphics mode for the specified device context.

CDC::GetHalftoneBrush

Retrieves a halftone brush.

CDC::GetKerningPairs

Retrieves the character kerning pairs for the font that is currently selected in the specified device context.

CDC::GetLayout

Retrieves the layout of a device context (DC). The layout can be either left to right (default) or right to left (mirrored).

CDC::GetMapMode

Retrieves the current mapping mode.

CDC::GetMiterLimit

Returns the miter limit for the device context.

CDC::GetNearestColor

Retrieves the closest logical color to a specified logical color that the given device can represent.

CDC::GetOutlineTextMetrics

Retrieves font metric information for TrueType fonts.

CDC::GetOutputCharWidth

Retrieves the widths of individual characters in a consecutive group of characters from the current font using the output device context.

CDC::GetOutputTabbedTextExtent

Computes the width and height of a character string on the output device context.

CDC::GetOutputTextExtent

Computes the width and height of a line of text on the output device context using the current font to determine the dimensions.

CDC::GetOutputTextMetrics

Retrieves the metrics for the current font from the output device context.

CDC::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.

CDC::GetPixel

Retrieves the RGB color value of the pixel at the specified point.

CDC::GetPolyFillMode

Retrieves the current polygon-filling mode.

CDC::GetROP2

Retrieves the current drawing mode.

CDC::GetSafeHdc

Returns CDC::m_hDC, the output device context.

CDC::GetStretchBltMode

Retrieves the current bitmap-stretching mode.

CDC::GetTabbedTextExtent

Computes the width and height of a character string on the attribute device context.

CDC::GetTextAlign

Retrieves the text-alignment flags.

CDC::GetTextCharacterExtra

Retrieves the current setting for the amount of intercharacter spacing.

CDC::GetTextColor

Retrieves the current text color.

CDC::GetTextExtent

Computes the width and height of a line of text on the attribute device context using the current font to determine the dimensions.

CDC::GetTextExtentExPointI

Retrieves the number of characters in a specified string that will fit within a specified space and fills an array with the text extent for each of those characters.

CDC::GetTextExtentPointI

Retrieves the width and height of the specified array of glyph indices.

CDC::GetTextFace

Copies the typeface name of the current font into a buffer as a null-terminated string.

CDC::GetTextMetrics

Retrieves the metrics for the current font from the attribute device context.

CDC::GetViewportExt

Retrieves the x- and y-extents of the viewport.

CDC::GetViewportOrg

Retrieves the x- and y-coordinates of the viewport origin.

CDC::GetWindow

Returns the window associated with the display device context.

CDC::GetWindowExt

Retrieves the x- and y-extents of the associated window.

CDC::GetWindowOrg

Retrieves the x- and y-coordinates of the origin of the associated window.

CDC::GetWorldTransform

Retrieves the current world-space to page-space transformation.

CDC::GradientFill

Fills rectangle and triangle structures with a gradating color.

CDC::GrayString

Draws dimmed (grayed) text at the given location.

CDC::HIMETRICtoDP

Converts HIMETRIC units into device units.

CDC::HIMETRICtoLP

Converts HIMETRIC units into logical units.

CDC::IntersectClipRect

Creates a new clipping region by forming the intersection of the current region and a rectangle.

CDC::InvertRect

Inverts the contents of a rectangle.

CDC::InvertRgn

Inverts the colors in a region.

CDC::IsPrinting

Determines whether the device context is being used for printing.

CDC::LineTo

Draws a line from the current position up to, but not including, a point.

CDC::LPtoDP

Converts logical units into device units.

CDC::LPtoHIMETRIC

Converts logical units into HIMETRIC units.

CDC::MaskBlt

Combines the color data for the source and destination bitmaps using the given mask and raster operation.

CDC::ModifyWorldTransform

Changes the world transformation for a device context using the specified mode.

CDC::MoveTo

Moves the current position.

CDC::OffsetClipRgn

Moves the clipping region of the given device.

CDC::OffsetViewportOrg

Modifies the viewport origin relative to the coordinates of the current viewport origin.

CDC::OffsetWindowOrg

Modifies the window origin relative to the coordinates of the current window origin.

CDC::PaintRgn

Fills a region with the selected brush.

CDC::PatBlt

Creates a bit pattern.

CDC::Pie

Draws a pie-shaped wedge.

CDC::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.

CDC::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.

CDC::PolyBezier

Draws one or more Bzier splines. The current position is neither used nor updated.

CDC::PolyBezierTo

Draws one or more Bzier splines, and moves the current position to the ending point of the last Bzier spline.

CDC::PolyDraw

Draws a set of line segments and Bzier splines. This function updates the current position.

CDC::Polygon

Draws a polygon consisting of two or more points (vertices) connected by lines.

CDC::Polyline

Draws a set of line segments connecting the specified points.

CDC::PolylineTo

Draws one or more straight lines and moves the current position to the ending point of the last line.

CDC::PolyPolygon

Creates two or more polygons that are filled using the current polygon-filling mode. The polygons may be disjoint or they may overlap.

CDC::PolyPolyline

Draws multiple series of connected line segments. The current position is neither used nor updated by this function.

CDC::PtVisible

Specifies whether the given point is within the clipping region.

CDC::RealizePalette

Maps palette entries in the current logical palette to the system palette.

CDC::Rectangle

Draws a rectangle using the current pen and fills it using the current brush.

CDC::RectVisible

Determines whether any part of the given rectangle lies within the clipping region.

CDC::ReleaseAttribDC

Releases m_hAttribDC, the attribute device context.

CDC::ReleaseOutputDC

Releases m_hDC, the output device context.

CDC::ResetDC

Updates the m_hAttribDC device context.

CDC::RestoreDC

Restores the device context to a previous state saved with SaveDC.

CDC::RoundRect

Draws a rectangle with rounded corners using the current pen and filled using the current brush.

CDC::SaveDC

Saves the current state of the device context.

CDC::ScaleViewportExt

Modifies the viewport extent relative to the current values.

CDC::ScaleWindowExt

Modifies the window extents relative to the current values.

CDC::ScrollDC

Scrolls a rectangle of bits horizontally and vertically.

CDC::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.

CDC::SelectClipRgn

Combines the given region with the current clipping region by using the specified mode.

CDC::SelectObject

Selects a GDI drawing object such as a pen.

CDC::SelectPalette

Selects the logical palette.

CDC::SelectStockObject

Selects one of the predefined stock pens, brushes, or fonts provided by Windows.

CDC::SetAbortProc

Sets a programmer-supplied callback function that Windows calls if a print job must be aborted.

CDC::SetArcDirection

Sets the drawing direction to be used for arc and rectangle functions.

CDC::SetAttribDC

Sets m_hAttribDC, the attribute device context.

CDC::SetBkColor

Sets the current background color.

CDC::SetBkMode

Sets the background mode.

CDC::SetBoundsRect

Controls the accumulation of bounding-rectangle information for the specified device context.

CDC::SetBrushOrg

Specifies the origin for the next brush selected into a device context.

CDC::SetColorAdjustment

Sets the color adjustment values for the device context using the specified values.

CDC::SetDCBrushColor

Sets the current brush color.

CDC::SetDCPenColor

Sets the current pen color.

CDC::SetGraphicsMode

Sets the current graphics mode for the specified device context.

CDC::SetLayout

Changes the layout of a device context (DC).

CDC::SetMapMode

Sets the current mapping mode.

CDC::SetMapperFlags

Alters the algorithm that the font mapper uses when it maps logical fonts to physical fonts.

CDC::SetMiterLimit

Sets the limit for the length of miter joins for the device context.

CDC::SetOutputDC

Sets m_hDC, the output device context.

CDC::SetPixel

Sets the pixel at the specified point to the closest approximation of the specified color.

CDC::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.

CDC::SetPolyFillMode

Sets the polygon-filling mode.

CDC::SetROP2

Sets the current drawing mode.

CDC::SetStretchBltMode

Sets the bitmap-stretching mode.

CDC::SetTextAlign

Sets the text-alignment flags.

CDC::SetTextCharacterExtra

Sets the amount of intercharacter spacing.

CDC::SetTextColor

Sets the text color.

CDC::SetTextJustification

Adds space to the break characters in a string.

CDC::SetViewportExt

Sets the x- and y-extents of the viewport.

CDC::SetViewportOrg

Sets the viewport origin.

CDC::SetWindowExt

Sets the x- and y-extents of the associated window.

CDC::SetWindowOrg

Sets the window origin of the device context.

CDC::SetWorldTransform

Sets the current world-space to page-space transformation.

CDC::StartDoc

Informs the device driver that a new print job is starting.

CDC::StartPage

Informs the device driver that a new page is starting.

CDC::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.

CDC::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.

CDC::StrokePath

Renders the specified path by using the current pen.

CDC::TabbedTextOut

Writes a character string at a specified location, expanding tabs to the values specified in an array of tab-stop positions.

CDC::TextOut

Writes a character string at a specified location using the currently selected font.

CDC::TransparentBlt

Transfers a bit-block of color data from the specified source device context into a destination device context, rendering a specified color transparent in the transfer.

CDC::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.

CDC::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.

Public Operators

Name

Description

CDC::operator HDC

Retrieves the handle of the device context.

Public Data Members

Name

Description

CDC::m_hAttribDC

The attribute-device context used by this CDC object.

CDC::m_hDC

The output-device context used by this CDC object.

Remarks

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 95/98, 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 provides two member functions, GetLayout and SetLayout, for reversing the layout of a device context, which does not inherit its layout from a window. Such right-to-left orientation is necessary for applications written for cultures, such as Arabic or Hebrew, where the character layout is not the European standard.

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.

Inheritance Hierarchy

CObject

CDC

Requirements

Header: afxwin.h

See Also

Reference

CObject Class

Hierarchy Chart

CPaintDC Class

CWindowDC Class

CClientDC Class

CMetaFileDC Class