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Drawing Arrows

, 30 Nov 2002
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How to draw arrows (with arrowheads) to an arbitrary DC.

Sample Image - Arrows.jpg

Excuse

Basically, there was a request for some code to draw arrows and I had never seen any. Plus, I'm not really in the mood to hang drapes or vacuum.

Using the code

This is a simple API for drawing lines with arrowheads. It looks like this:

// ARROWSTRUCT
//
// Defines the attributes of an arrow.
typedef struct tARROWSTRUCT {
    int nWidth;     // width (in pixels) of the full base of the arrowhead
    float fTheta;   // angle (in radians) at the arrow tip between the two
                    //  sides of the arrowhead
    bool bFill;     // flag indicating whether or not the arrowhead should be
                    //  filled
} ARROWSTRUCT;

// ArrowTo()
//
// Draws an arrow, using the current pen and brush, from the current position
//  to the passed point using the attributes defined in the ARROWSTRUCT.
void ArrowTo(HDC hDC, int x, int y, ARROWSTRUCT *pArrow);
void ArrowTo(HDC hDC, const POINT *lpTo, ARROWSTRUCT *pArrow);

Simply fill an ARROWSTRUCT with the desired attributes, make sure the current DC position is correct (MoveTo(), etc.), and call one of the two ArrowTo() functions. The size parameters (nWidth and fTheta) are defined as follows:

Technique

This goes back to high-school algebra and trigonometry. The ArrowTo() function first builds a vector of the full line. Then it calculates the points for the sides of the arrowhead based on the nWidth and fTheta attributes you pass. Badda-boom-badda-bing, you got your arrowhead.

Here's some pseudo-pseudocode:

lineVector = toPoint - fromPoint
lineLength = length of lineVector

// calculate point at base of arrowhead
tPointOnLine = nWidth / (2 * (tanf(fTheta) / 2) * lineLength);
pointOnLine = toPoint + -tPointOnLine * lineVector

// calculate left and right points of arrowhead
normalVector = (-lineVector.y, lineVector.x)
tNormal = nWidth / (2 * lineLength)
leftPoint = pointOnLine + tNormal * normalVector
rightPoint = pointOnLine + -tNormal * normalVector

History

  • December 1 2002 - Created.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Jamie Hale
Web Developer
Canada Canada
No Biography provided

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Comments and Discussions

 
QuestionUrgent Pin
Member 104154789-May-14 5:34
memberMember 104154789-May-14 5:34 
GeneralMy vote of 5 Pin
manoj kumar choubey22-Feb-12 0:02
membermanoj kumar choubey22-Feb-12 0:02 
SuggestionSome suggestions Pin
herohuyongtao8-Oct-11 20:52
memberherohuyongtao8-Oct-11 20:52 
GeneralCorrecting the math for better arrow heads Pin
bstrack17-Feb-10 8:09
memberbstrack17-Feb-10 8:09 
Generalquestion Pin
Luo Rui4-Dec-06 2:24
memberLuo Rui4-Dec-06 2:24 
GeneralFreaks out in release mode Pin
mark-w24-Sep-06 8:30
membermark-w24-Sep-06 8:30 
GeneralRe: Freaks out in release mode Pin
mark-w24-Sep-06 8:55
membermark-w24-Sep-06 8:55 
GeneralRe: Freaks out in release mode Pin
Jamie Hale25-Sep-06 4:23
memberJamie Hale25-Sep-06 4:23 
GeneralRe: Freaks out in release mode Pin
mark-w30-Sep-06 19:30
membermark-w30-Sep-06 19:30 
AnswerRe: Freaks out in release mode Pin
ClemensR18-Sep-07 5:10
memberClemensR18-Sep-07 5:10 
GeneralRe: Freaks out in release mode Pin
kkokkal14-Jan-08 20:23
memberkkokkal14-Jan-08 20:23 
GeneralJust another approach Pin
prcarp10-May-06 3:27
memberprcarp10-May-06 3:27 
GeneralRe: Just another approach Pin
rsantos0123-Nov-06 4:54
memberrsantos0123-Nov-06 4:54 
GeneralI am looking for a simple MFC Control with Draw Area Pin
p2002ad25-May-05 6:14
memberp2002ad25-May-05 6:14 
GeneralLength of arrow Pin
Hemant kulkarni2-Dec-02 20:11
memberHemant kulkarni2-Dec-02 20:11 
GeneralRe: Length of arrow Pin
Philippe Lhoste2-Dec-02 23:07
memberPhilippe Lhoste2-Dec-02 23:07 
GeneralRe: Length of arrow Pin
Philippe Lhoste3-Dec-02 1:53
memberPhilippe Lhoste3-Dec-02 1:53 
GeneralRe: Length of arrow Pin
Jamie Hale3-Dec-02 4:50
memberJamie Hale3-Dec-02 4:50 
GeneralRe: Length of arrow Pin
Jamie Hale3-Dec-02 4:51
memberJamie Hale3-Dec-02 4:51 
GeneralHeight of the arrowhead Pin
MetalRob14-Nov-10 23:48
memberMetalRob14-Nov-10 23:48 
GeneralRe: Height of the arrowhead Pin
Jamie Hale15-Nov-10 0:00
memberJamie Hale15-Nov-10 0:00 
GeneralRe: Height of the arrowhead Pin
MetalRob15-Nov-10 0:17
memberMetalRob15-Nov-10 0:17 
GeneralRe: Height of the arrowhead Pin
MetalRob15-Nov-10 0:18
memberMetalRob15-Nov-10 0:18 
GeneralAnother way: matrix transformation (don't be scared it's easy!) :) Pin
Damir Valiulin2-Dec-02 13:05
memberDamir Valiulin2-Dec-02 13:05 
GeneralRe: Another way: matrix transformation (don't be scared it's easy!) :) Pin
Jamie Hale3-Dec-02 4:48
memberJamie Hale3-Dec-02 4:48 
Generalnice, but GDI+ can do it better Pin
afisser2-Dec-02 2:15
memberafisser2-Dec-02 2:15 
GeneralRe: nice, but GDI+ can do it better Pin
Jamie Hale2-Dec-02 5:27
memberJamie Hale2-Dec-02 5:27 
GeneralRe: nice, but GDI+ can do it better Pin
Philippe Lhoste2-Dec-02 23:01
memberPhilippe Lhoste2-Dec-02 23:01 
GeneralFirst non-joke thread! Pin
Nishant S1-Dec-02 14:11
editorNishant S1-Dec-02 14:11 
GeneralRe: First non-joke thread! Pin
Shog91-Dec-02 15:07
memberShog91-Dec-02 15:07 
GeneralRe: First non-joke thread! Pin
Jamie Hale1-Dec-02 17:02
memberJamie Hale1-Dec-02 17:02 
QuestionWhere are the other 7? Pin
Nishant S1-Dec-02 14:09
editorNishant S1-Dec-02 14:09 

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