TransparencyKey Does Not Work on Non Development Computer

gagster · #1 (**permalink**) April 5th, 2010, 02:24 AM

In chapter 10 "Windows Forms", one of the properties that is discussed is the TransparencyKey. I decided to write a simple program to try this out. When I run the program on my development computer, whether inside the IDE or not, it works as expected. If I copy the exe to another computer and run it, the background shows up - it is not transparent.

I downloaded the sample program from the web site and found I get the same results. Is there anything I need to do to get this to work on other computers?

Thanks,

Greg

Rod Stephens · #2 (**permalink**) April 29th, 2010, 12:39 AM

Sorry for the slow reply. I lost track of this in my inbox.

I don't know why this would work on one machine and not another. Perhaps there's something graphics related installed by Visual Studio, but that would be a bit weird.

I have noticed that TransparencyKey doesn't seem to work as well as it used to.

One workaround is to set the form's Region property to a region that restricts it. For example:

Code:

    Private Sub Form1_Load(ByVal sender As System.Object, _
     ByVal e As System.EventArgs) Handles MyBase.Load
        ' Make points to define a polygon for the form.
        Dim pts(0 To 9) As PointF
        Dim cx As Single = Me.ClientSize.Width * 0.5
        Dim cy As Single = Me.ClientSize.Height * 0.5
        Dim r1 As Single = Me.ClientSize.Height * 0.45
        Dim r2 As Single = Me.ClientSize.Height * 0.25
        Dim theta As Single = -PI / 2
        Dim dtheta As Single = 2 * PI / 10
        For i As Integer = 0 To 9 Step 2
            pts(i) = New PointF( _
                cx + r1 * Cos(theta), _
                cy + r1 * Sin(theta))
            theta += dtheta
            pts(i + 1) = New PointF( _
            cx + r2 * Cos(theta), _
            cy + r2 * Sin(theta))
            theta += dtheta
        Next i

        ' Use the polygon to define a GraphicsPath.
        Dim path As New GraphicsPath()
        path.AddPolygon(pts)

        ' Make a region from the path.
        Dim form_region As New Region(path)

        ' Restrict the form to the region.
        Me.Region = form_region
    End Sub

I'll post a complete example in the next couple days at http://www.vb-helper.com/howto_net_set_form_region.html. (No time now.)

gagster · #3 (**permalink**) April 29th, 2010, 02:01 AM

After posting my question, I went over to Microsoft's knowledgebase and discovered this is a known bug. Here's their article BUG: The TransparencyKey property is not effective...

I tried the workaround they gave but still couldn't get it working. Part of the problem is that they gave a VB2005 example and I wasn't sure where that code should go in VB2008.

Anyway, I was just playing around with this out of curiosity. So, while I wished it worked, it's not critical.

On another topic, I'm slowly reading through your book. This is mainly a review for me. I just want to make sure I'm not missing anything. I just read your discussion of AndAlso and OrElse. While the example you gave of having a time consuming function call as the second operand is a good one, I think you should also have used this example:

Code:

if x <> 0 And y/x > 1 then

vs

Code:

if x <> 0 AndAlso y/x >1 then

The "And" version looks like it should work, but will throw an exception if x is zero, while the "AndAlso" version works as expected.

Thanks for the help.

Greg

Rod Stephens · #4 (**permalink**) April 29th, 2010, 09:02 AM

That's a good example. Using the first test to ensure that the second makes sense before trying the second. It's easy enough to do with nested Ifs but this is cleaner.

Need to download code?

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