"Armin Zingler" <az.nospam@freenet.de> wrote in message
news:402903d3$0$13018$9b622d9e@news.freenet.de...
> Hi again,
>
> I've got another transparency problem.
> Q: How can I make _parts_ of a Form _semi_transparent?
>
> - Opacity affects the _whole_ Form.
> - The TransparencyKey makes areas _completely_ transparent.
>
> So both are not what I am looking for. The following example uses the
alpha
> channel:
>
> Private Sub Form1_Load( _
> ByVal sender As System.Object, ByVal e As System.EventArgs) _
> Handles MyBase.Load
>
> setstyle(ControlStyles.AllPaintingInWmPaint, True)
> setstyle(ControlStyles.ResizeRedraw, True)
> setstyle(ControlStyles.UserPaint, True)
> End Sub
>
>
> Protected Overrides Sub OnPaintBackground( _
> ByVal pevent As System.Windows.Forms.PaintEventArgs)
> 'MyBase.OnPaintBackground(pevent)
> End Sub
>
> Protected Overrides Sub OnPaint( _
> ByVal e As System.Windows.Forms.PaintEventArgs)
>
> Dim b As SolidBrush
> Dim r1, r2 As Rectangle
>
> b = New SolidBrush(Color.FromArgb(128, 255, 0, 0))
> r1 = Me.ClientRectangle
> r1.Width \= 2
> r2 = r1
> r2.X = r1.Width
>
> e.Graphics.FillRectangle(Brushes.Red, r1)
> e.Graphics.FillRectangle(b, r2)
>
> b.Dispose()
> End Sub
>
> Now the right half is semitransparent so that the window beneath shines
> through, but if I move the Form, the windows beneath are not painted,
> so the result of the right half is not always a mixture of the window(s)
> beneath and the Form content. I know this happens because my Form is
> not repainted when moved. I'd like to have the same effect as when
> using the Opacity property, i.e. everything is repainted to get a
> mixture result. I've also played with the SupportsTransparentBackColor
style
> but it didn't help also.
>
> (How) can this be solved?
>
>
> Armin
>

> The only way to do this is using p/invoke and using the
> UpdateLayeredWindow method. This enables you to create a per-pixel
> alpha image with varying levels of transparency and display it on
> screen.
>
> The CreateParams can be modified to use the WS_EX_LAYERED style.
>
> I'm afraid I don't have any demo code for this as yet.