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Class: GDIChord in Category Microsoft Visual Basic 6 : Graphics from Total Visual SourceBook

Class that draws a Chord, using Windows API GDI calls in VB6.

A chord is a region bounded by the intersection of an ellipse and a line segment, called a "secant". Imagine an arc whose end-points are connected by a straight line. The routines in this class allow you to draw the chord by calling the Windows API Chord function.

Procedure List

Procedure Name	Type	Description
(Declarations)	Declarations	Declarations and private variables for the CGDIChord class.
BorderColor	Property	Get the current value of the color used to draw the chord.
BorderWidth	Property	Get the current value of the BorderWidth used to draw the chord.
Bottom	Property	Get the Bottom location of the bounding rectangle for the chord.
FillColor	Property	Get the current value of the color used to fill the chord.
ForegroundMixMode	Property	Get the current value of the ForegroundMixMode property, which defines how colors from the pen and the colors in the existing image are to be combined. The value should be one of the enumerated raster op values exposed in EnumChordRasterOps, or the equivalent VBA/VB6 "DrawModeConstants", such as vbCopyPen, vbXorPen etc. See "Drawing Constants" in the VBA/VB6 on-line help.
Left	Property	Get the Left location of the bounding rectangle for the chord.
PenStyle	Property	Get the value of the style used to draw the chord. The value of this property should be set to one of the Windows API Pen Style constants (PS_SOLID, PS_DASHDOT etc.) which are exposed as EnumArcChordStyles constants in this class.
Right	Property	Get the Right location of the bounding rectangle for the chord.
Top	Property	Get the Top location of the bounding rectangle for the chord.
Class_Initialize	Initialize	Set initial values to defaults which may be overridden with property settings.
DrawChord	Method	Draw a Chord on a selected device. The arc of the chord is drawn along the edge of an ellipse bounded by an imaginary rectangle, whose dimensions are specified in the Left, Top, Right, and Bottom properties. The end points of the chord's arc are determined by the arguments to this method.
DrawChordByAngle	Method	Draw a Chord from the starting and ending angles. The arc of the chord is drawn along the outside of an imaginary ellipse bounded by the dimensions of a rectangle specified in the Left, Top, Bottom and Right properties.
DrawChordByAngleSweep	Method	Draw a Chord from a starting angle for the specified number of degrees. The arc of the chord is drawn along the outside of an imaginary ellipse bounded by the dimensions of a rectangle specified in the Left, Top, Bottom and Right properties.
TranslateVBColor	Private	Translates VBA/VB6 color constants for system colors into GDI equivalents. VBA/VB6 color constants, such as vbRed, vbBlue, or values returned using the QBColor() or RGB() functions, can be used directly for the color values used with Windows API calls. However, the VBA/VB6 color constants for system colors (vbButtonFace, vb3DShadow etc.) do not map correctly to those expected by Windows. This function accepts either form of constant and translates the value, if necessary, into the equivalent value expected by the Windows GDI subsystem.

Example Code for Using Class: GDIChord

' Example of the CGDIChord class
'
' To try this example, do the following:
' 1. Create a new form
' 2. Paste all the code from this example to the new form's module
' 3. Run the form and click on the background. The chords are drawn
'    based on the location of the click

Private Sub Form_MouseUp(Button As Integer, Shift As Integer, x As Single, Y As Single)

  Dim GDIChord As CGDIChord
  Set GDIChord = New CGDIChord

  With GDIChord
    .Left = ScaleX(X, vbTwips, vbPixels) - 100
    .Top = ScaleY(Y, vbTwips, vbPixels) - 100
    .Right = ScaleX(X, vbTwips, vbPixels) + 100
    .Bottom = ScaleY(Y, vbTwips, vbPixels) + 100

    .BorderColor = vbBlue
    .BorderWidth = 1
    .FillColor = vbYellow
    .ForegroundMixMode = croR2_COPYPEN
    .PenStyle = cpsPS_SOLID

    ' Draw a chord by specifying the radial end-points
    .BorderColor = vbBlue
    .DrawChord Me.hDC, .Right, .Bottom + 10, .Right - 10, .Top

    ' Draw a chord by specifying the angles
    .PenStyle = cpsPS_DASH
    .BorderColor = vbGreen
    .FillColor = vbRed
    .DrawChordByAngle Me.hDC, 90, 180

    ' Draw a chord by specifying the starting angle and an offset
    .BorderColor = vbBlue
    .FillColor = vbMagenta
    .DrawChordByAngleSweep Me.hDC, 180, 90

  End With

End Sub

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