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# Drawing Arrows

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I would like to know if there are any routines that, given
a line (x1,y1)-(x2,y2), will automatically draw an arrow-
head on it pointing in the right direction.
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## View Solution Only

Commented:
There's no built in function for drawing arrows, but the following function will do it.

Private Function Arrow(x1 As Long, y1 As Long, x2 As Long, y2 As Long, Direction As Long) As Long
Dim xdiff As Long

xdiff = x2 - x1
xdiff = xdiff / 5

Form1.Line (x1, y1)-(x2, y2)
If Direction = 1 Then
x1 = x2 - xdiff
y1 = y2 - xdiff
Form1.Line (x2, y2)-(x1, y1)
y1 = y1 + (xdiff * 2)
Form1.Line (x2, y2)-(x1, y1)
Else
x2 = x1 + xdiff
y2 = y1 - xdiff
Form1.Line (x1, y1)-(x2, y2)
y2 = y2 + (xdiff * 2)
Form1.Line (x1, y1)-(x2, y2)
End If

End Function

Just pass it the four endpoints of the line, and the direction you want the arrow to point.  1 is right and 2 is left.  It could be expanded to also include up and down, and probably diagonals also.

Commented:
It should be possible to draw the arrow in ANY direction, at
ANY angle. There should be no need to pass a direction value
to the function as the direction is determined by the position
of the start and end points of the line. Thanks for trying though:)

Commented:
Following subroutine draws an arrow head at the line end point. The sample is written to draw an arrow formed by two line sections, but you can modify it to draw with an arrow style you like. It assumes the usage of a type

Private Type LineType
xStart As Integer
yStart As Integer
xEnd As Integer
yEnd As Integer
End Type

as the argument.

Private Sub DrawLineWithArrow(MyLine As LineType)
Dim xTemp As Single
Dim yTemp As Single

' Rotation coefficients
Dim sCos As Single
Dim sSin As Single
Dim xDiff As Integer
Dim yDiff As Integer

' Arrow coordinates
Dim xTip As Single
Dim yTip As Single
Dim xCorner1 As Single
Dim yCorner1 As Single
Dim xCorner2 As Single
Dim yCorner2 As Single

' Arrow dimensions. Set them to comply with your scale.
Const xOffset = 5 'Lenght
Const yOffset = 2 'Width

With MyLine
' Calculate rotation coefficients
xDiff = .xEnd - .xStart
yDiff = .yEnd - .yStart
sCos = xDiff / Sqr(xDiff * xDiff + yDiff * yDiff)
sSin = Sqr(1 - sCos * sCos)
If yDiff < 0 Then
sSin = -Abs(sSin)
End If
If xDiff < 0 Then
sCos = -Abs(sCos)
End If

' Calculate arrow coordinates assuming horizontally
' positioned arrow at the line end point
xTip = .xEnd
yTip = .yEnd
' Translate origo to the the arrow tip
xCorner1 = -xOffset '.xEnd - xOffset - xTip etc
yCorner1 = yOffset
xCorner2 = -xOffset
yCorner2 = -yOffset
' Rotate and translate points
xTemp = xCorner1 * sCos - yCorner1 * sSin
yTemp = xCorner1 * sSin + yCorner1 * sCos
xCorner1 = xTemp + xTip ' translate to original coordinates
yCorner1 = yTemp + yTip

xTemp = xCorner2 * sCos - yCorner2 * sSin
yTemp = xCorner2 * sSin + yCorner2 * sCos
xCorner2 = xTemp + xTip ' translate to original coordinates
yCorner2 = yTemp + yTip

'Draw line
Picture1.Line (.xStart, .yStart)-(.xEnd, .yEnd)
' Draw arrow
Picture1.Line (xTip, yTip)-(xCorner1, yCorner1)
Picture1.Line (xTip, yTip)-(xCorner2, yCorner2)
End With
End Sub

Commented:
That's the only thing I couldn't come up with is the formula to calculate the endpoints from the given angle.  Been too many years since Trig.

Commented:
I'm afraid the solution doesn't work. The line:

sCos = xDiff / Sqr(xDiff * xDiff + yDiff * yDiff)

will produce an overflow error for all but the tiniest of lines, and even for the tiny lines, I see no arrow head.

Commented:
This one is on us!
(Get your first solution completely free - no credit card required)

Commented:
Ooops .....

I meant to write, change all variable declarations having type integer to type single or double.

Commented:
Great! It works perfectly now. Thankyou very much :)

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