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

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

This class lets you draw an arbitrary polygon made up of a collection of straight-line segments, whose end-points are specified by the X and Y position in pixels. Specify the number of points in the polygon by setting the PointCount property. Then set the points between 1 and PointCount to valid X and Y point positions. The routines in this class allow you to draw the shape by calling the Windows API DrawPolygon function.

Procedure Name Type Description
(Declarations) Declarations Declarations and private variables for the CGDIPolygon class.
BorderColor Property Get the current value of the color used to draw the polygon.
BorderWidth Property Get the current value of the BorderWidth used to draw the polygon.
BrushStyle Property Get the current style used to fill the polygon. The value of this property should be set to one of the Windows API Brush Style constants (BS_SOLID, BS_HOLLOW, BS_HATCHED etc.) which are exposed as EnumPolygonBrushStyles constants in this class.
FillColor Property Get the current value of the color used to fill the polygon.
FillMode Property Get the current mode used to fill complex polygons with overlapping sections. The value of this property should be set to one of the Windows API Fill Mode constants (ALTERNATE or WINDING), which are exposed as EnumPolygonFillModes constants in this class. This property controls how the polygon is filled if it contains overlapping segments (for example, if the polygon creates the shape of a star, pfmALTERNATE will fill in the "points"; pfmWINDING will fill in the entire star).
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 EnumPolygonRasterOps, or the equivalent VBA/VB6 "DrawModeConstants", such as vbCopyPen, vbXorPen etc. See "Drawing Constants" in the VBA/VB6 on-line help.
HatchStyle Property Get the current value of the style used to fill the polygon when the BrushStyle is set to hatched. The value of this property should be set to one of the Windows API Hatch Style constants (HS_HORIZONTAL, HS_BDIAGONAL, HS_CROSS etc.) which are exposed as EnumPolgyonHatchStyles constants in this class.
PenStyle Property Get the value of the style used to draw the polygon. 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 EnumPolygonPenStyles constants in this class.
PointCount Property Get the current number of points in the polygon.
Class_Initialize Initialize Set initial values to defaults which may be overridden with property settings.
DrawPolyGon Method Draw a PolyGon on a selected device. Specify the points making up the polygon by using the SetPoint method. When all of the points have been specified, use this method to actually draw the polygon on the selected device.
GetPoint Method Modifies the passed lngX and lngY parameters with the X and Y values of the specified point. If you wish to determine the X and Y values of a point which was previously added to the collection with the SetPoint method, call this method. The X and Y coordinate values are placed into the passed 'lngX' and 'lngY' parameters to the function.
SetPoint Method Set the X and Y coordinates of one of the points in the polygon.
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 of the CGDIPolygon 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. A star is drawn on the background of the form

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

  Dim lngSaveScale As Long
  Dim GDIPolygon As CGDIPolygon

  Set GDIPolygon = New CGDIPolygon

  ' Erase the form background

  ' Set form's scalemode to 3 (Pixels) for easier calculation
  lngSaveScale = Me.ScaleMode
  Me.ScaleMode = vbPixels

  With GDIPolygon
    .BorderColor = vbBlue
    .BorderWidth = 1
    .FillColor = vbYellow
    .BrushStyle = pbsBS_SOLID
    .FillMode = pfmALTERNATE

    ' A star requires 5 points
    .PointCount = 5

    ' Set the points for the start
    .SetPoint 1, Me.ScaleWidth * 0.5, 0
    .SetPoint 2, Me.ScaleWidth * 0.8, Me.ScaleHeight
    .SetPoint 3, Me.ScaleWidth * 0.1, Me.ScaleHeight * 0.33
    .SetPoint 4, Me.ScaleWidth * 0.9, Me.ScaleHeight * 0.33
    .SetPoint 5, Me.ScaleWidth * 0.2, Me.ScaleHeight

    ' Draw the star
    .DrawPolyGon Me.hDC

  End With

  ' Restore original scale
  Me.ScaleMode = lngSaveScale

End Sub

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