How do I suspend painting for a control and its children?

Question

I have a control which I have to make large modifications to. I\'d like to completely prevent it from redrawing while I do that - SuspendLayout and ResumeLayout aren\'t eno

Answer 1

This is even simpler, and perhaps hacky - as I can see a lot of GDI muscle on this thread, and is obviously only a good fit for certain scenarios. YMMV

In my scenario, I use what I'll refer to as a "Parent" UserControl - and during the Load event, I simply remove the control-to-be-manipulated from the Parent's .Controls collection, and the Parent's OnPaint takes care of completely painting the child control in whatever special way.. fully taking the child's paint capabilities offline.

Now, I hand off my child paint routine to an extension method based off this concept from Mike Gold for printing windows forms.

Here I'm needing a sub-set of labels to render perpendicular to the layout:

Then, I exempt the child control from being painted, with this code in the ParentUserControl.Load event handler:

Private Sub ParentUserControl_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    SetStyle(ControlStyles.UserPaint, True)
    SetStyle(ControlStyles.AllPaintingInWmPaint, True)

    'exempt this control from standard painting: 
    Me.Controls.Remove(Me.HostedControlToBeRotated) 
End Sub

Then, in the same ParentUserControl, we paint the control-to-be-manipulated from the ground up:

Protected Overrides Sub OnPaint(e As PaintEventArgs)
    'here, we will custom paint the HostedControlToBeRotated instance...

    'twist rendering mode 90 counter clockwise, and shift rendering over to right-most end 
    e.Graphics.SmoothingMode = Drawing2D.SmoothingMode.AntiAlias
    e.Graphics.TranslateTransform(Me.Width - Me.HostedControlToBeRotated.Height, Me.Height)
    e.Graphics.RotateTransform(-90)
    MyCompany.Forms.CustomGDI.DrawControlAndChildren(Me.HostedControlToBeRotated, e.Graphics)

    e.Graphics.ResetTransform()
    e.Graphics.Dispose()

    GC.Collect()
End Sub

Once you host the ParentUserControl somewhere, e.g. a Windows Form - I'm finding that my Visual Studio 2015 renders the form correctly at Design Time as well as runtime:

Now, since my particular manipulation rotates the child control 90 degrees, I'm sure all the hot spots and interactivity has been destroyed in that region - but, the problem I was solving was all for a package label that needed to preview and print, which worked out fine for me.

If there are ways to reintroduce the hot spots and control-ness to my purposely orphaned control - I'd love to learn about that someday (not for this scenario, of course, but.. just to learn). Of course, WPF supports such craziness OOTB.. but.. hey.. WinForms is so much fun still, amiright?