A view referencing a View that's not a peer (same superview) in Dim/Pos should not be allowed

I was debugging tests and came across this test:

https://github.com/gui-cs/Terminal.Gui/blob/33c9a5fad44256ab1ade0d9ac478dab6af89b9b6/UnitTests/Types/DimTests.cs#LL541C3-L585C4

		public void DimCombine_Do_Not_Throws ()
		{
			Application.Init (new FakeDriver ());


			var t = Application.Top;


			var w = new Window ("w") {
				Width = Dim.Width (t) - 2,
				Height = Dim.Height (t) - 2
			};
			var f = new FrameView ("f");
			var v1 = new View ("v1") {
				Width = Dim.Width (w) - 2,
				Height = Dim.Height (w) - 2
			};
			var v2 = new View ("v2") {
				Width = Dim.Width (v1) - 2,
				Height = Dim.Height (v1) - 2
			};


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


			f.Width = Dim.Width (t) - Dim.Width (v2);
			f.Height = Dim.Height (t) - Dim.Height (v2);


			t.Ready += (s, e) => {
				Assert.Equal (80, t.Frame.Width);
				Assert.Equal (25, t.Frame.Height);
				Assert.Equal (78, w.Frame.Width);
				Assert.Equal (23, w.Frame.Height);
				Assert.Equal (6, f.Frame.Width);
				Assert.Equal (6, f.Frame.Height);
				Assert.Equal (76, v1.Frame.Width);
				Assert.Equal (21, v1.Frame.Height);
				Assert.Equal (74, v2.Frame.Width);
				Assert.Equal (19, v2.Frame.Height);
			};


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


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

I have decided this test is totally bogus because views are referencing superviews.

This code would guard against this:

		internal void CollectPos (Pos pos, View from, ref HashSet<View> nNodes, ref HashSet<(View, View)> nEdges)
		{
			switch (pos) {
			case Pos.PosView pv:
				if (!from.InternalSubviews.Contains (pv.Target)) {
					throw new InvalidOperationException ($"View {pv.Target} is not a subview of {from}");
				}
				if (pv.Target != this) {
					nEdges.Add ((pv.Target, from));
				}
				foreach (var v in from.InternalSubviews) {
					CollectAll (v, ref nNodes, ref nEdges);
				}
				return;
			case 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);
				}
				break;
			}
		}

		internal void CollectDim (Dim dim, View from, ref HashSet<View> nNodes, ref HashSet<(View, View)> nEdges)
		{
			switch (dim) {
			case Dim.DimView dv:
				if (!from.InternalSubviews.Contains (dv.Target)) {
					throw new InvalidOperationException ($"View {dv.Target} is not a subview of {from}");
				}
				if (dv.Target != this) {
					nEdges.Add ((dv.Target, from));
				}
				foreach (var v in from.InternalSubviews) {
					CollectAll (v, ref nNodes, ref nEdges);
				}
				return;
			case Dim.DimCombine dc:
				foreach (var v in from.InternalSubviews) {
					CollectDim (dc.left, from, ref nNodes, ref nEdges);
					CollectDim (dc.right, from, ref nNodes, ref nEdges);
				}
				break;
			}
		}

And this test would verify:

		[Fact]
		public void Dim_Referencing_SuperView_Throws ()
		{
			var super = new View ("super") {
				Width = 10,
				Height = 10
			};
			var view = new View ("view") {
				Width = Dim.Width (super),	// this is not allowed
				Height = Dim.Height (super),    // this is not allowed
			};

			super.Add (view);
			super.BeginInit ();
			super.EndInit ();
			Assert.Throws<InvalidOperationException> (() => super.LayoutSubviews ());
		}

This breaks a lot of existing code (e.g. TileView does this internally). So I’m not sure I’m correct.

Please debate 😉.

Thanks.

[tig]

I’m going to close this issue. I think @BDisp shows an interesting use-case.

[BDisp]

@tig with the last fix in the #2504, the rightLabel now have the right Pos.AnchorEnd (1) instead of Pos.AnchorEnd (13).