FlowLayoutPanel Height bug when using AutoSize

Question

I have a form holding a TableLayout with 1 column and 3 rows that holds 2 FlowLayoutPanels and a Text box. All Rows are AutoSize, and the column is set to Percentage=100%.

Each FlowLayoutPanel holds several TextBoxes. The FlowLayoutPanels are set: LeftToRight, AutoSize=true, GrowAndShrink, Docking=Fill.

The outline is:

Form
    TableLayout (Dock=Fill)
        FlowLayoutPanel(Dock=Fill, AutoSize=True, GrowShrink)
           More controls
        FlowLayoutPanel(Dock=Fill, AutoSize=True, GrowShrink)
           More controls
        TextBox(Dock=Fill, MultiLine=true)

The problem is if I place the FlowLayoutPanel inside a GroupBox which are also set to be AutoSize=true, the FlowLayoutPanel Height are not set correctly and it shows the TextBoxes in 1 line cutting some TextBoxes out of the form.

The outline is:

Form
    TableLayout (Dock=Fill)
        GroupBox (Dock=Fill, AutoSize=True, GrowShrink) 
            FlowLayoutPanel(Dock=Fill, AutoSize=True, GrowShrink)
               More controls
        GroupBox (Dock=Fill, AutoSize=True, GrowShrink) 
            FlowLayoutPanel(Dock=Fill, AutoSize=True, GrowShrink)
               More controls
        TextBox(Dock=Fill, MultiLine=true)

BTW,the same thing happens if I use instead of a GroupBox, a Panel or even a UserControl to hold the FlowLayoutPanel.

BTW 2, this happens even without the TableLayout. I tried placing the GroupBox (with the FlowLayoutPanel) on an AutoSized Form and I get the same behavior.

What I think the problem is that when the FlowLayoutPanel is in another container that is also AutoSized it fails to pass to it's container is preferred size.

What can be done to override this bug??

Please help Thanks, Yoram

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p.s: I must use the GroupBox to have a nice frame around the TextBoxes.

Solution 1

Had encountered this problem too, and tried to figure out how to easily resolve this. Although the @GertArnold's answer did help, it felt a bit cumbersome, and I searched for another solution.

What I found was that the Flow Panel's autosize logic was working on the 'minimum' requirements, and by adding a blank Panel, of minimum height I was able to force the Flow Panel's width, thus making all other child controls to be visible.

so in the example above the final layout would be:

Form
    TableLayout (Dock=Fill)
        GroupBox (Dock=Fill, AutoSize=True, GrowShrink) 
            FlowLayoutPanel(Dock=Fill, AutoSize=True, GrowShrink)
                Panel(Dock=Fill, Height = 1, MinimumSize = new System.Drawing.Size( Form.ClientSize.Width - TableLayout.Padding.Horizontal, 1))
                More controls
        GroupBox (Dock=Fill, AutoSize=True, GrowShrink) 
            FlowLayoutPanel(Dock=Fill, AutoSize=True, GrowShrink)
                Panel(Dock=Fill, Height = 1, MinimumSize = new System.Drawing.Size( Form.ClientSize.Width - TableLayout.Padding.Horizontal, 1))
                More controls
        TextBox(Dock=Fill, MultiLine=true)

Hope this helps.

Solution 2

As you dock the FlowLayoutPanel in the GroupBox (or other containers), you may as well leave their AutoSize=false. I'm not sure, but this may make the groupbox the 'leading' control when it comes to sizing.

---

Edit (after your comment)

'Leading control' are my words trying to express that groupbox size would determine that of the FLP, it's not some official term. The problem is that docking and autosizing are fighting one another by nature and someone should take, well, control. Which can only be done when docking and autosizing are cut back and by programming the resize events yourself.

After playing around a bit I finally came up with this model:

Form
    TableLayout (Dock=Fill)
        GroupBox () 
            FlowLayoutPanel(Dock=Fill)
               More controls

And the resize event:

private void Form1_Resize(object sender, EventArgs e)
{
    this.SuspendLayout();
    this.groupBox.Width = this.Width - 20;
    this.groupBox.Height = 
        this.flowLayoutPanel.GetPreferredSize(this.groupBox.Size).Height + 20;
    this.ResumeLayout();
}

I hope I understood you well. At least this may point you in the right direction.

Comments

[Yoram]

I can't use AutoSize=false for the FlowLayuotPanel because when the Form is streched by the user, the GroupBox is stretched and the FlowLayoutPanel is stretched with it, and it can hold all it's controls in one line I want it to AutoSize to one line thus reducing the GroupBox height.

[Yoram]

BTW: can you post here a link that explains what you ment about "leading' control regarding sizing? This can lead to solving the issue because I had no idea about 'leading' controls.. Thanks

[Yoram]

I really appreciate your replies. I'll have to get back to this in a couple of days because I moved to a different assignment. I'll post back when I can check your solution. Thanks!!

[Yoram]

Hey GertArnold. You did it! Your solution works. The only change I had to add is triggering the Form1_Resize event when the application starts so it would resize everything according to that code. Thanks again!!

[Gert Arnold]

You're welcome. It taught me some new things about the windows forms resizing snake pit too.