How to rotate a line shape 90 Degrees? - vb.net

Question

I am going to have a form with 60 Line Shapes (Using Visual Studios PowerPack). I would like the user to be able to rotate the shapes 90 Degrees using the left and right buttons on the keyboard.
What would be the best way to do this? I have tried other methods however this amounts to 1000's of lines of code, I am still learning and I want to know the best practices.
Thanks a lot!

Answer 1

I'm assuming for the moment that you've already written the part to handle the geometry once, and are asking about how to re-use the code, without duplicating it for 60 lines. This matters because it's not 100% clear from the question whether you're rotating around the mid-point or around the starting point, as the LineShape type does make a distinction between the Starting and Ending points. Without that information, I can't write the geometry code for you.
The first part isn't so bad. We just setup a few methods that can handle rotating any line:
'Note that rotating a line 90 degrees around it's midpoint
' will give the same result whether you go clockwise or counterclockwise,
' but I figure you'll want to adapt this for other shapes later, or that
' you're rotating around the line's starting point
Private Sub RotateClockwise(ByVal line As LineShape)
'Code to rotate the passed line clockwise here
Dim x1 As Integer = line.X1
Dim y1 As Integer = line.Y1
Dim x2 As Integer = line.X2
Dim y2 As Integer = line.Y2
End Sub
Private Sub RotateCounterclockwise(ByVal line As LineShape)
'Code to rotate the passed line counter-clockwise here
End Sub
Private Sub LineShape_KeyDown(Byval sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs)
'Which line?
Dim line As LineShape = TryCast(sender, LineShape)
If line Is Nothing Then Exit Sub
'Left key?
If e.KeyCode = Keys.Left Then RotateCounterclockwise(line)
'Right key?
If e.KeyCode = Keys.Right Then RotateClockwise(line)
End Sub
This is where it gets tricky. Notice that the event handler above is missing the Handles keyword. We want to hookup the KeyDown event handler for all of your LineShape controls to this one method. This will be a bit repetitive, as it means one additional line of code for each line on your form, but it's better than needing to write the above code for all of your lines:
Dim Lines As New List(Of LineShape)()
Lines.Add(LineShape1)
Lines.Add(LineShape2)
'...
Lines.Add(LineShape60)
For Each Line As LineShape In Lines
AddHandler Line.KeyDown, AddressOf LineShape_KeyDown
Next
That code goes in your form's constructor after the InitializeComponent() method.
I could do better still if the LineShape type were a true control (For EAch Line In Me.Controls.OfType(Of LineShape)()), but the docs show this is actually a Component, and not a Control.

Answer 2

Alternatively, you can subclass LineShape and build "rotatability" into your new class as :
Imports Microsoft.VisualBasic.PowerPacks
Public Class MySmartLine
Inherits LineShape
Private Sub RotateClockwise()
'Code to rotate clockwise here
Me.X1 = ...
Me.X2 = ...
End Sub
Private Sub RotateAntiClockwise()
'Code to rotate anti clockwise here
End Sub
Protected Overrides Sub OnKeyDown(ByVal e As System.Windows.Forms.KeyEventArgs)
MyBase.OnKeyDown(e)
If e.KeyCode = Keys.Left Then
RotateAntiClockwise()
End If
If e.KeyCode = Keys.Right Then
RotateClockwise()
End If
End Sub
End Class
After building your project, a custom MySmartLine component will appear in your toolbox and you can use it in place of LineShape.