GetHeightRequiredForSubViews dose not return what I expect

[LokiMidgard]

I have a View with several labels. Every Label has the Bottom of the previous element as top.

I use this local Helper Function for it:

this.ViewportSettings |= ViewportSettingsFlags.HasScrollBars;
        View? lastElement = null;
        void Add(View view, int? spacing = null)
        {
            if (lastElement == null)
            {
                view.Y = Pos.Absolute(spacing ?? 0);
            }
            else
            {
                view.Y = Pos.Bottom(lastElement) + (spacing ?? 0);
            }
            view.X = Pos.Absolute(0);
            view.Width = Dim.Fill();
            
            this.Add(view);
            lastElement = view;
        }

My assumption was that if I call GetHeightRequiredForSubViews it returns the sum of the height of every Label.
However it only returns the height of the Viewport. I wanted to use that value to set the contentHeight so I can enable scrolling.

I appreciate any help :)
Thanks in advance

[gyanu2507]

GetHeightRequiredForSubViews() is returning the viewport on purpose in your setup, not the stacked labels.

By default ContentSizeTracksViewport is true, so content size == visible size. HasScrollBars only shows bars when content is larger than the viewport. If you never call SetContentSize, there is nothing to scroll, and the helper that feeds on auto-height / content size collapses to the viewport.

Pos.Bottom(lastElement) also does not give those labels a height until layout has run. Calling the helper before the first layout pass will not sum Dim.Fill() children (Fill does not contribute to auto height unless you give a minimumContentDim).

After you Add the labels, compute a content size and set it:

int y = 0;
foreach (var sub in this.SubViews)
{
    // after Layout(), sub.Frame.Height is real
    y = Math.Max(y, sub.Frame.Y + sub.Frame.Height);
}
this.SetContentSize(new Size(this.GetContentSize().Width, y));
this.ViewportSettings |= ViewportSettingsFlags.HasVerticalScrollBar;

Or give the container Height = Dim.Auto(DimAutoStyle.Content) if you want the view itself to grow to the labels instead of scrolling. Docs: https://gui-cs.github.io/Terminal.Gui/docs/scrolling.html

[LokiMidgard]

I got it working. From the doku of View there seems to be an Event after Layout:

Events

LayoutStarted - Before layout begins
LayoutComplete - After layout completes
FrameChanged - When Frame changes
ViewportChanged - When Viewport changes

But I did not find a way To register. Neither Event nor method to Overload. The Only thing I found was SubViewsLaidOut. That seem to do the trick.

Thats an Imaga of the current console App:

Thank you for your help.