.NET PowerPacks RectangleShape flickers on form re

问题:

I can do something as simple as:

1. Create a new .NET form application
2. Put a single RectangleShape onto the form

3. add the following into the InitializeComponent method in the designer code

   Me.SetStyle(ControlStyles.AllPaintingInWmPaint Or _
       ControlStyles.UserPaint Or _
       ControlStyles.DoubleBuffer, True)
   Me.UpdateStyles()
   

4. Run the program
5. Resize the form
6. Watch angrily as the rectangle flickers

Is it possible to get rid of this? Or is the ShapeContainer internally flawed and I need to find a different solution?

回答1:

It's fairly flawed. It uses its own window that's overlaid onto the form with the WS_EX_TRANSPARENT style turned on. That style makes it invisible, but also prevents any kind of double-buffering from working properly. Double-buffering the form has no effect, wrong window.

It is otherwise a rather expensive way to draw shapes. The cheap and flicker-free way is using e.Graphics.FillRectangle() in the form's OnPaint() override or Paint event handler.

回答2:

I've never used the ShapeContainer but when ever I do custom graphics like that, I create a subclass for a Panel and in the constructor of my subclass I set DoubleBuffered to true.

More specific code example here.