CPen Class

Encapsulates a Windows graphics device interface (GDI) pen.

Syntax

class CPen : public CGdiObject

Members

Public Constructors

Public Methods

Public Operators

Remarks

For more information on using CPen, see Graphic Objects.

Inheritance Hierarchy

CObject

CGdiObject

CPen

Requirements

Header: afxwin.h

CPen::CPen

Constructs a CPen object.

CPen();

CPen(
    int nPenStyle,
    int nWidth,
    COLORREF crColor);

CPen(
    int nPenStyle,
    int nWidth,
    const LOGBRUSH* pLogBrush,
    int nStyleCount = 0,
    const DWORD* lpStyle = NULL);

Parameters

nPenStyle
Specifies the pen style. This parameter in the first version of the constructor can be one of the following values:

• PS_SOLID Creates a solid pen.

• PS_DASH Creates a dashed pen. Valid only when the pen width is 1 or less, in device units.

• PS_DOT Creates a dotted pen. Valid only when the pen width is 1 or less, in device units.

• PS_DASHDOT Creates a pen with alternating dashes and dots. Valid only when the pen width is 1 or less, in device units.

• PS_DASHDOTDOT Creates a pen with alternating dashes and double dots. Valid only when the pen width is 1 or less, in device units.

• PS_NULL Creates a null pen.

• PS_INSIDEFRAME Creates a pen that draws a line inside the frame of closed shapes produced by the Windows GDI output functions that specify a bounding rectangle (for example, the Ellipse, Rectangle, RoundRect, Pie, and Chord member functions). When this style is used with Windows GDI output functions that don't specify a bounding rectangle (for example, the LineTo member function), the drawing area of the pen isn't limited by a frame.

The second version of the CPen constructor specifies a combination of type, style, end cap, and join attributes. The values from each category should be combined by using the bitwise "or" (|) operator. The pen type can be one of the following values:

• PS_GEOMETRIC Creates a geometric pen.

• PS_COSMETIC Creates a cosmetic pen.

  The second version of the CPen constructor adds the following pen styles for nPenStyle:

• PS_ALTERNATE Creates a pen that sets every other pixel. (This style is applicable only for cosmetic pens.)

• PS_USERSTYLE Creates a pen that uses a styling array supplied by the user.

  The end cap can be one of the following values:

• PS_ENDCAP_ROUND End caps are round.

• PS_ENDCAP_SQUARE End caps are square.

• PS_ENDCAP_FLAT End caps are flat.

  The join can be one of the following values:

• PS_JOIN_BEVEL Joins are beveled.

• PS_JOIN_MITER Joins are mitered when they are within the current limit set by the SetMiterLimit function. If the join exceeds this limit, it's beveled.

• PS_JOIN_ROUND Joins are round.

nWidth
Specifies the width of the pen.

• For the first version of the constructor, a value of 0 will be treated similarly to a value of 1, except that the width will not be affected by scale-transform operations that are in effect for the Graphics object that the pen is used for; the width will always be 1 pixel.

• For the second version of the constructor, if nPenStyle is PS_GEOMETRIC, the width is given in logical units. If nPenStyle is PS_COSMETIC, the width must be set to 1.

crColor
Contains an RGB color for the pen.

pLogBrush
Points to a LOGBRUSH structure. If nPenStyle is PS_COSMETIC, the lbColor member of the LOGBRUSH structure specifies the color of the pen and the lbStyle member of the LOGBRUSH structure must be set to BS_SOLID. If nPenStyle is PS_GEOMETRIC, all members must be used to specify the brush attributes of the pen.

nStyleCount
Specifies the length, in doubleword units, of the lpStyle array. This value must be zero if nPenStyle isn't PS_USERSTYLE.

lpStyle
Points to an array of doubleword values. The first value specifies the length of the first dash in a user-defined style, the second value specifies the length of the first space, and so on. This pointer must be NULL if nPenStyle isn't PS_USERSTYLE.

Remarks

If you use the constructor with no arguments, you must initialize the resulting CPen object with the CreatePen, CreatePenIndirect, or CreateStockObject member functions.

If you use the constructor that takes arguments, then no further initialization is necessary. The constructor with arguments can throw an exception if errors are encountered, while the constructor with no arguments will always succeed.

Example

// Create a solid red pen of width 2.
CPen myPen1(PS_SOLID, 2, RGB(255, 0, 0));

// Create a geometric pen.
LOGBRUSH logBrush;
logBrush.lbStyle = BS_SOLID;
logBrush.lbColor = RGB(0, 255, 0);
CPen myPen2(PS_DOT | PS_GEOMETRIC | PS_ENDCAP_ROUND, 2, &logBrush);

CPen::CreatePen

Creates a logical cosmetic or geometric pen with the specified style, width, and brush attributes, and attaches it to the CPen object.

BOOL CreatePen(
    int nPenStyle,
    int nWidth,
    COLORREF crColor);

BOOL CreatePen(
    int nPenStyle,
    int nWidth,
    const LOGBRUSH* pLogBrush,
    int nStyleCount = 0,
    const DWORD* lpStyle = NULL);

Parameters

nPenStyle
Specifies the style for the pen. For a list of possible values, see the nPenStyle parameter in the CPen constructor.

nWidth
Specifies the width of the pen.

• For the first version of CreatePen, a value of 0 will be treated similarly to a value of 1, except that the width will not be affected by scale-transform operations that are in effect for the Graphics object that the pen is used for; the width will always be 1 pixel.

• For the second version of CreatePen, if nPenStyle is PS_GEOMETRIC, the width is given in logical units. If nPenStyle is PS_COSMETIC, the width must be set to 1.

crColor
Contains an RGB color for the pen.

pLogBrush
Points to a LOGBRUSH structure. If nPenStyle is PS_COSMETIC, the lbColor member of the LOGBRUSH structure specifies the color of the pen and the lbStyle member of the LOGBRUSH structure must be set to BS_SOLID. If nPenStyle is PS_GEOMETRIC, all members must be used to specify the brush attributes of the pen.

nStyleCount
Specifies the length, in doubleword units, of the lpStyle array. This value must be zero if nPenStyle isn't PS_USERSTYLE.

lpStyle
Points to an array of doubleword values. The first value specifies the length of the first dash in a user-defined style, the second value specifies the length of the first space, and so on. This pointer must be NULL if nPenStyle isn't PS_USERSTYLE.

Return Value

Nonzero if successful, or zero if the method fails.

Remarks

The first version of CreatePen initializes a pen with the specified style, width, and color. The pen can be subsequently selected as the current pen for any device context.

Pens that have a width greater than 1 pixel should always have either the PS_NULL, PS_SOLID, or PS_INSIDEFRAME style.

If a pen has the PS_INSIDEFRAME style and a color that doesn't match a color in the logical color table, the pen is drawn with a dithered color. The PS_SOLID pen style can't be used to create a pen with a dithered color. The style PS_INSIDEFRAME is identical to PS_SOLID if the pen width is less than or equal to 1.

The second version of CreatePen initializes a logical cosmetic or geometric pen that has the specified style, width, and brush attributes. The width of a cosmetic pen is always 1; the width of a geometric pen is always specified in world units. After an application creates a logical pen, it can select that pen into a device context by calling the CDC::SelectObject function. After a pen is selected into a device context, it can be used to draw lines and curves.

• If nPenStyle is PS_COSMETIC and PS_USERSTYLE, the entries in the lpStyle array specify lengths of dashes and spaces in style units. A style unit is defined by the device in which the pen is used to draw a line.

• If nPenStyle is PS_GEOMETRIC and PS_USERSTYLE, the entries in the lpStyle array specify lengths of dashes and spaces in logical units.

• If nPenStyle is PS_ALTERNATE, the style unit is ignored and every other pixel is set.

When an application no longer requires a given pen, it should call the CGdiObject::DeleteObject member function or destroy the CPen object so the resource is no longer in use. An application shouldn't delete a pen when the pen is selected in a device context.

Example

CPen myPen1, myPen2;

// Create a solid red pen of width 2.
myPen1.CreatePen(PS_SOLID, 2, RGB(255, 0, 0));

// Create a geometric pen.
LOGBRUSH logBrush;
logBrush.lbStyle = BS_SOLID;
logBrush.lbColor = RGB(0, 255, 0);
myPen2.CreatePen(PS_DOT | PS_GEOMETRIC | PS_ENDCAP_ROUND, 2, &logBrush);

CPen::CreatePenIndirect

Initializes a pen that has the style, width, and color given in the structure pointed to by lpLogPen.

BOOL CreatePenIndirect(LPLOGPEN lpLogPen);

Parameters

lpLogPen
Points to the Windows LOGPEN structure that contains information about the pen.

Return Value

Nonzero if the function is successful; otherwise 0.

Remarks

Pens that have a width greater than 1 pixel should always have either the PS_NULL, PS_SOLID, or PS_INSIDEFRAME style.

If a pen has the PS_INSIDEFRAME style and a color that doesn't match a color in the logical color table, the pen is drawn with a dithered color. The PS_INSIDEFRAME style is identical to PS_SOLID if the pen width is less than or equal to 1.

Example

LOGPEN logpen;
CPen   cMyPen;

// Get the LOGPEN of an existing pen.
penExisting.GetLogPen(&logpen);

// Change the color to red and the width to 2.
logpen.lopnWidth.x = 2;
logpen.lopnColor = RGB(255, 0, 0);

// Create my pen using the new settings.
cMyPen.CreatePenIndirect(&logpen);

CPen::FromHandle

Returns a pointer to a CPen object given a handle to a Windows GDI pen object.

static CPen* PASCAL FromHandle(HPEN hPen);

Parameters

hPen
HPEN handle to Windows GDI pen.

Return Value

A pointer to a CPen object if successful; otherwise NULL.

Remarks

If a CPen object isn't attached to the handle, a temporary CPen object is created and attached. This temporary CPen object is valid only until the next time the application has idle time in its event loop, at which time all temporary graphic objects are deleted. In other words, the temporary object is only valid during the processing of one window message.

Example

// Convert an HPEN to a CPen*.
// NOTE: hPen is a valid pen handle.
CPen* pPen = CPen::FromHandle(hPen);

CPen::GetExtLogPen

Gets an EXTLOGPEN underlying structure.

int GetExtLogPen(EXTLOGPEN* pLogPen);

Parameters

pLogPen
Points to an EXTLOGPEN structure that contains information about the pen.

Return Value

Nonzero if successful; otherwise 0.

Remarks

The EXTLOGPEN structure defines the style, width, and brush attributes of a pen. For example, call GetExtLogPen to match the particular style of a pen.

See the following topics in the Windows SDK for information about pen attributes:

• GetObject

• EXTLOGPEN

• LOGPEN

• ExtCreatePen

Example

The following code example demonstrates calling GetExtLogPen to retrieve a pen's attributes, and then create a new, cosmetic pen with the same color.

EXTLOGPEN extlogpen;
penExisting.GetExtLogPen(&extlogpen);
CPen penOther;
LOGBRUSH LogBrush = { extlogpen.elpBrushStyle, extlogpen.elpColor,
   extlogpen.elpHatch };
penOther.CreatePen(PS_COSMETIC, 1, &LogBrush);

CPen::GetLogPen

Gets a LOGPEN underlying structure.

int GetLogPen(LOGPEN* pLogPen);

Parameters

pLogPen
Points to a LOGPEN structure to contain information about the pen.

Return Value

Nonzero if successful; otherwise 0.

Remarks

The LOGPEN structure defines the style, color, and pattern of a pen.

For example, call GetLogPen to match the particular style of pen.

See the following topics in the Windows SDK for information about pen attributes:

• GetObject

• LOGPEN

Example

The following code example demonstrates calling GetLogPen to retrieve a pen character, and then create a new, solid pen with the same color.

LOGPEN logpen;
penExisting.GetLogPen(&logpen);
CPen penOther(PS_SOLID, 0, logpen.lopnColor);

CPen::operator HPEN

Gets the attached Windows GDI handle of the CPen object.

operator HPEN() const;

Return Value

If successful, a handle to the Windows GDI object represented by the CPen object; otherwise NULL.

Remarks

This operator is a casting operator, which supports direct use of an HPEN object.

For more information about using graphic objects, see the article Graphic Objects in Windows SDK.

Example

// Create a solid red pen of width 2.
CPen myPen(PS_SOLID, 2, RGB(255, 0, 0));

// Get the handle of the pen object.
HPEN hPen = (HPEN)myPen;

See also

CGdiObject Class
Hierarchy Chart
CBrush Class