duplication avoidance when writing to picturebox and printer

Question

So occasionally program in VB6 but I never solved this problem.

I have a Private Sub to draw lots of stuff to a picturebox like lines, text, pictures. Lots and lots of lines of code. But then i want to use same lines to draw to a printer object. But I don't know how to do it.

For example:

private sub command1_click()
    picture1.print "hello there"
    etc etc etc
end sub
private sub command2_click()
    printer.print "hello world"
    etc etc etc
    printer.print
end sub

to be

public sub pictureengine(action....)
    if action = draw then picturebox is selected for output
    if action = print then printer object is selected output 
    <object/control>.print "hello world"
    etc etc etc
    if action = print then printer.enddoc printer.print
end sub

There should be an alias to use controls/objects. Thanks in advance

Answer 1

I was faced with this exact issue. I decided to abstract away the details of the PictureBox, Printer, or any other surface by implementing Interfaces. You will end up with 3 classes:

• ISurface
• CPrinterSurface
• CPictureBoxSurface

The ISurface Class defines the interface and contains no code:

Option Explicit

Public Sub Create(ByRef SurfaceObject As Object)
End Sub

Public Sub AddLine(ByVal StartX As Double, _
                   ByVal StartY As Double, _
                   ByVal EndX As Double, _
                   ByVal EndY As Double, _
                   Optional ByVal PenColor As Long = vbWhite, _
                   Optional ByVal PenSize As Integer = 1, _
                   Optional ByVal PenStyle As DrawStyleConstants = vbSolid)
End Sub

Public Sub AddCircle(ByVal StartX As Double, _
                     ByVal StartY As Double, _
                     ByVal Radius As Double, _
                     Optional ByVal PenColor As Long = vbWhite, _
                     Optional ByVal PenSize As Integer = 1, _
                     Optional ByVal PenStyle As DrawStyleConstants = vbSolid)
End Sub

The CPrinterSurface Class implements the interface. This is where you add code.

Option Explicit

Implements ISurface

Private oPrinter As Printer

Private Sub ISurface_Create(SurfaceObject As Object)
   Set oPrinter = SurfaceObject
End Sub

Private Sub ISurface_AddLine(ByVal StartX As Double, _
                             ByVal StartY As Double, _
                             ByVal EndX As Double, _
                             ByVal EndY As Double, _
                             Optional ByVal PenColor As Long = 16777215, _
                             Optional ByVal PenSize As Integer = 1, _
                             Optional ByVal PenStyle As DrawStyleConstants = 0&)
   oPrinter.DrawWidth = PenSize
   oPrinter.DrawStyle = PenStyle
   oPrinter.ForeColor = PenColor       
   oPrinter.Line (StartX, StartY)-(EndX, EndY), PenColor
End Sub

Private Sub ISurface_AddCircle(ByVal StartX As Double, _
                               ByVal StartY As Double, _
                               ByVal Radius As Double, _
                               Optional ByVal PenColor As Long = 16777215, _
                               Optional ByVal PenSize As Integer = 1, _
                               Optional ByVal PenStyle As DrawStyleConstants = 0&)
   oPrinter.DrawWidth = PenSize
   oPrinter.DrawStyle = PenStyle
   oPrinter.ForeColor = PenColor
   oPrinter.Circle (StartX, StartY), Radius, PenColor
End Sub

The CPictureBoxSurface Class also implements the interface.

Option Explicit

Implements ISurface

Private oPictureBox As PictureBox

Private Sub ISurface_Create(SurfaceObject As Object)
   Set oPictureBox = SurfaceObject
End Sub

Private Sub ISurface_AddLine(ByVal StartX As Double, _
                             ByVal StartY As Double, _
                             ByVal EndX As Double, _
                             ByVal EndY As Double, _
                             Optional ByVal PenColor As Long = 16777215, _
                             Optional ByVal PenSize As Integer = 1, _
                             Optional ByVal PenStyle As DrawStyleConstants = 0&)
   oPictureBox.DrawWidth = PenSize
   oPictureBox.DrawStyle = PenStyle
   oPictureBox.ForeColor = PenColor       
   oPictureBox.Line (StartX, StartY)-(EndX, EndY), PenColor
End Sub

Private Sub ISurface_AddCircle(ByVal StartX As Double, _
                               ByVal StartY As Double, _
                               ByVal Radius As Double, _
                               Optional ByVal PenColor As Long = 16777215, _
                               Optional ByVal PenSize As Integer = 1, _
                               Optional ByVal PenStyle As DrawStyleConstants = 0&)
   oPictureBox.DrawWidth = PenSize
   oPictureBox.DrawStyle = PenStyle
   oPictureBox.ForeColor = PenColor
   oPictureBox.Circle (StartX, StartY), Radius, PenColor
End Sub

The Main App. Create an EXE project containing the logic to generically produce your drawing. Swap out the surface, and one codebase can draw to any implemented surface. Your project tree will consist of the main form with a PictureBox and a Button, and the 3 classes described above. Here is the code for the main form:

Option Explicit

Private MySurface As ISurface

Private Sub cmdCreate_Click()
   Set MySurface = New CPictureBoxSurface
   MySurface.Create Picture1
   MySurface.AddCircle 1000, 1000, 500, vbRed
   MySurface.AddCircle 1500, 1500, 500, vbBlue
End Sub

The code presented above eliminates duplication when you have multiple surfaces. It has been stripped down for clarity and to highlight the basic architecture. Hopefully you will be able to expound upon these concepts for your application.