Views - View.Height += 1 does not have the expected behavior

[jmperricone]

Before I use view.Height = view.Subviews.Count;, I had it in another way where I did view.Height += 1;
I remove a lot of other views with Dim and Pos to other views, thinking maybe was circular reference or something.
But no, the problem is just that line .... view.Height += 1;

If you try this, it gets exponentially slower.

This is beacuse Dim.Combine. After 3 times,
view.Height == {Dim.Combine(Dim.Combine(Dim.Combine(Dim.Absolute(0)+Dim.Absolute(1))+Dim.Absolute(1))+Dim.Absolute(1))}

Is this the expected behavior for this case ???

Maybe if it's the same instance, combine should behave differently, because I think that view.Height += x is something very basic to have such a behavior.

public override void Setup ()
{
  var view = new View () { X = 0, Y = 0, Width = 20, Height = 0 };
  var field = new TextField () { X = 0, Y = Pos.Bottom (view), Width = 20 };
  
  field.KeyDown += (k) => {
	  if (k.KeyEvent.Key == Key.Enter) {
  
		  var label = new Label (field.Text) { X = 0, Y = view.Subviews.Count, Width = 20 };
		  
                  field.Text = "";
  
		  view.Add (label);
  
                  // works
		  view.Height = view.Subviews.Count;
                  
                  // don't try this at home
		  // view.Height += 1;
	  }
  };
  
  Win.Add (view);
  Win.Add (field);
}

[jmperricone]

[BDisp]

That is the way that Pos and Dim works, but why don't do that?

view.Height = view.Bounds.Height + 1;

[BDisp]

Maybe if it's the same instance, combine should behave differently, because I think that view.Height += x is something very basic to have such a behavior.

I agree. Do you have some solution for this?

[BDisp]

I already found the bug and will submit a PR, unless you already have your own fix, which if it is the case please then say anything.

[BDisp]

I think it's here.

			void CollectPos (Pos pos, View from, ref HashSet<View> nNodes, ref HashSet<(View, View)> nEdges)
			{
				if (pos is Pos.PosView pv) {
					if (pv.Target != this) {
						nEdges.Add ((pv.Target, from));
					}
					foreach (var v in from.InternalSubviews) {
						CollectAll (v, ref nNodes, ref nEdges);
					}
					return;
				}
				if (pos is Pos.PosCombine pc) {
					foreach (var v in from.InternalSubviews) {
						CollectPos (pc.left, from, ref nNodes, ref nEdges);
						CollectPos (pc.right, from, ref nNodes, ref nEdges);
					}
				}
			}

and I changed to:

			void CollectPos (Pos pos, View from, ref HashSet<View> nNodes, ref HashSet<(View, View)> nEdges)
			{
				if (pos is Pos.PosView pv) {
					if (pv.Target != this) {
						nEdges.Add ((pv.Target, from));
					}
					foreach (var v in from.InternalSubviews) {
						CollectAll (v, ref nNodes, ref nEdges);
					}
					return;
				}
				if (pos is Pos.PosCombine pc) {
					foreach (var v in from.InternalSubviews) {
						CollectPos (pc.left, v, ref nNodes, ref nEdges);
						CollectPos (pc.right, v, ref nNodes, ref nEdges);
					}
				}
			}

But now I get error while running the tests here:

		[Fact]
		public void PosCombine_Do_Not_Throws ()
		{
			Application.Init (new FakeDriver (), new FakeMainLoop (() => FakeConsole.ReadKey (true)));

			var t = Application.Top;

			var w = new Window ("w") {
				X = Pos.Left (t) + 2,
				Y = Pos.Top (t) + 2
			};
			var f = new FrameView ("f");
			var v1 = new View ("v1") {
				X = Pos.Left (w) + 2,
				Y = Pos.Top (w) + 2
			};
			var v2 = new View ("v2") {
				X = Pos.Left (v1) + 2,
				Y = Pos.Top (v1) + 2
			};

			f.Add (v1, v2);
			w.Add (f);
			t.Add (w);

			f.X = Pos.X (t) + Pos.X (v2) - Pos.X (v1);
			f.Y = Pos.Y (t) + Pos.Y (v2) - Pos.Y (v1);

			t.Ready += () => {
				Assert.Equal (0, t.Frame.X);
				Assert.Equal (0, t.Frame.Y);
				Assert.Equal (2, w.Frame.X);
				Assert.Equal (2, w.Frame.Y);
				Assert.Equal (2, f.Frame.X);
				Assert.Equal (2, f.Frame.Y);
				Assert.Equal (4, v1.Frame.X);
				Assert.Equal (4, v1.Frame.Y);
				Assert.Equal (6, v2.Frame.X);
				Assert.Equal (6, v2.Frame.Y);
			};

			Application.Iteration += () => Application.RequestStop ();

			Application.Run ();
			Application.Shutdown ();
		}

Can we try to come to some conclusion together?

[BDisp]

I also have errors in the following scenarios:

Dialogs
MessageBoxes
Progress

[BDisp]

Well, the problem is nothing related to it. It is only related to Pos/Dim operators. I'll fix it.

[jmperricone]

@BDisp Sorry I couldn't help you.

That is the way that Pos and Dim works, but why don't do that?

view.Height = view.Bounds.Height + 1;

Yes, there are many ways to do this, but I think that operators should work as expected.