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VB 6 Helper Newsletter
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Rod Stephens
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Apr 09, 2009 10:49 PDT
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Special thanks to Steve Smerker for posting a review of my database book
on the Barnes and Noble Web site:
http://search.barnesandnoble.com/Beginning-Database-Design-Solutions/Rod-Stephens/e/9780470385494/?itm=1#TABS
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This week I've posted Visual Basic 6 and Visual Basic .NET versions of a
simple drawing program that lets you show or hide a grid and turn grid
snapping on and off. If you compare them, you'll see many of the biggest
differences between drawing in Visual Basic Classic and Visual Basic
.NET.
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Have a great week and thanks for subscribing!
Rod
RodSte-@vb-helper.com
Books To Keep: http://www.BooksToKeep.com
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*** Now Available ***
Beginning Database Design Solutions
http://www.amazon.com/exec/obidos/ASIN/0470385499/vbhelper/
Visual Basic 2008 Programmer's Reference
http://www.amazon.com/exec/obidos/ASIN/0470182628/vbhelper/
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VB6 Contents:
1. New HowTo: Make a simple drawing program with a "snap to" grid and
rules in Visual Basic 6
Both Contents:
2. New Links
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<VB6>
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1. New HowTo: Make a simple drawing program with a "snap to" grid and
rules in Visual Basic 6
http://www.vb-helper.com/howto_rulers_grid.html
http://www.vb-helper.com/HowTo/howto_rulers_grid.zip
When you press the mouse down on the main drawing canvas, the code
starts drawing. It sets m_Drawing to True so it can remember that it is
drawing. It calls SnapToGrid to snap the current point to the nearest
grid point and saves that point. It invalidates the drawing area to
redraw and calls ShowMousePosition to show the mouse position in the
rulers usin the "drawing" color.
' Start drawing a line.
Private Sub picCanvas_MouseDown(ByVal sender As Object, ByVal e As
System.Windows.Forms.MouseEventArgs) Handles picCanvas.MouseDown
' Only on left mouse down.
If Button <> vbLeftButton Then Exit Sub
m_Drawing = True
' Start drawing.
m_X1 = x
m_Y1 = y
SnapToGrid m_X1, m_Y1
m_X2 = m_X1
m_Y2 = m_Y1
picCanvas.Refresh
ShowMousePosition m_X2, m_Y2
End Sub
Subroutine SnapToGrid snaps a point to the nearest grid location. It
determines how many times the grid's size fits into the available canvas
size, rounding to the nearest integer. It then multiplies that number by
the grid size so get the nearest grid location.
' Snap the point to the nearest grid location.
Private Sub SnapToGrid(ByRef X As Integer, ByRef Y As Integer)
Dim ix As Integer
Dim iy As Integer
' If grid snap is off, do nothing.
If Not m_SnapToGrid Then Exit Sub
ix = CInt(x / m_GridX)
iy = CInt(y / m_GridY)
x = ix * m_GridX
y = iy * m_GridY
End Sub
Subroutine ShowMousePosition saves a point's coordinates and invalidates
the two rulers to make them redraw.
' Show the mouse position on the rulers.
Private Sub ShowMousePosition(ByVal X As Integer, ByVal Y As Integer)
m_MouseX = x
m_MouseY = y
picTopRuler.Refresh
picLeftRuler.Refresh
End Sub
The main canvas's MouseMove evnet handler saves the current mouse
position, snaps it to the grid, shows the mouse position, and redraws
the main canvas to show the new line being drawn.
' Continue drawing.
Private Sub picCanvas_MouseMove(ByVal sender As Object, ByVal e As
System.Windows.Forms.MouseEventArgs) Handles picCanvas.MouseMove
m_X2 = x
m_Y2 = y
SnapToGrid m_X2, m_Y2
' Show the mouse position on the rulers.
ShowMousePosition m_X2, m_Y2
' Redraw.
If m_Drawing Then picCanvas.Refresh
End Sub
The MouseUp event handler shows the mouse position in the non-drawing
color. It then saves the new line segement and redraws to show it in the
non-drawing color.
' Finish drawing.
Private Sub picCanvas_MouseUp(ByVal sender As Object, ByVal e As
System.Windows.Forms.MouseEventArgs) Handles picCanvas.MouseUp
If Not m_Drawing Then Exit Sub
m_Drawing = False
' Show the mouse position in the non-drawing color.
ShowMousePosition m_X2, m_Y2
' Save the new line.
m_NumSegments = m_NumSegments + 1
ReDim Preserve m_Segments(1 To m_NumSegments)
m_Segments(m_NumSegments).x1 = m_X1
m_Segments(m_NumSegments).y1 = m_Y1
m_Segments(m_NumSegments).x2 = m_X2
m_Segments(m_NumSegments).y2 = m_Y2
picCanvas.Refresh
End Sub
The main canvas's Paint event handler clears the canvas. Then if
m_ShowGrid is True, it draws the grid. It then draws any existing line
segments and finally, if a new line is being drawn, it draws that line.
' Draw the lines.
Private Sub picCanvas_Paint(ByVal sender As Object, ByVal e As
System.Windows.Forms.PaintEventArgs) Handles picCanvas.Paint
Dim x, y, i As Integer
picCanvas.Cls
' Draw the grid.
If m_ShowGrid Then
For x = 0 To picCanvas.ScaleWidth Step m_GridX
For y = 0 To picCanvas.ScaleHeight Step m_GridY
picCanvas.PSet (x, y), m_ColorGrid
Next y
Next x
End If
' Draw existing lines.
For i = 1 To m_NumSegments
picCanvas.Line (m_Segments(i).x1,
m_Segments(i).y1)-(m_Segments(i).x2, m_Segments(i).y2), m_ColorOldLine
Next i
' Draw the new line.
If m_Drawing Then
picCanvas.Line (m_X1, m_Y1)-(m_X2, m_Y2), m_ColorNewLine
End If
End Sub
The top ruler's Paint event handler clears the control. It then draws
the tick marks using the grid's spacing and giving greater length to
every 5 and 10 tick marks. Finally it draws the mouse's position in an
appropriate color. The Left ruler's Paint event handler works similarly.
' Draw the top ruler.
Private Sub picTopRuler_Paint(ByVal sender As Object, ByVal e As
System.Windows.Forms.PaintEventArgs) Handles picTopRuler.Paint
Dim y1 As Integer
Dim y2 As Integer
Dim y3 As Integer
Dim y4 As Integer
Dim x As Integer
Dim i As Integer
picTopRuler.Cls
y1 = picTopRuler.ScaleHeight
y2 = (2 * picTopRuler.ScaleHeight) \ 3
y3 = picTopRuler.ScaleHeight \ 3
y4 = 0
x = 0
For i = 0 To picTopRuler.ScaleWidth \ m_GridX
If i Mod 10 = 0 Then
picTopRuler.Line (x, y1)-(x, y4), m_ColorGrid
ElseIf i Mod 5 = 0 Then
picTopRuler.Line (x, y1)-(x, y3), m_ColorGrid
Else
picTopRuler.Line (x, y1)-(x, y2), m_ColorGrid
End If
x = x + m_GridX
Next i
' Show the mouse position.
If m_Drawing Then
picTopRuler.Line (m_MouseX, y1)-(m_MouseX, 0),
m_ColorRulerDrawing
Else
picTopRuler.Line (m_MouseX, y1)-(m_MouseX, 0),
m_ColorRulerNormal
End If
End Sub
Download the example to see additional details such as how the menus let
you show or hide the grid and turn grid snapping on and off.
This example is fairly basic and there are lots of other features you
could add such as zooming, panning, drawing other shapes, and so forth.
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<Both>
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2. New Links
InvestInTech: Tips for Working With Microsoft Software
http://www.investintech.com/content/tipsmicrosoftsoftware
A brief description of Exchange and Sharepoint, plus links to more
informationn about them and .NET programming in general.
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