support static boxes that go outside the available size

pkg/gui/boxlayout/boxlayout.go

@@ -96,6 +96,11 @@ func ArrangeWindows(root *Box, x0, y0, width, height int) map[string]Dimensions
 		var boxSize int
 		if child.isStatic() {
 			boxSize = child.Size
+			// assuming that only one static child can have a size greater than the
+			// available space. In that case we just crop the size to what's available
+			if boxSize > availableSize {
+				boxSize = availableSize
+			}
 		} else {
 			// TODO: consider more evenly distributing the remainder
 			boxSize = unitSize * child.Weight

pkg/gui/boxlayout/boxlayout_test.go

@@ -179,6 +179,27 @@ func TestArrangeWindows(t *testing.T) {
 				)
 			},
 		},
+		{
+			"Box with static child with size too large",
+			&Box{Direction: COLUMN, Children: []*Box{{Size: 11, Window: "static"}, {Weight: 1, Window: "dynamic1"}, {Weight: 2, Window: "dynamic2"}}},
+			0,
+			0,
+			10,
+			10,
+			func(result map[string]Dimensions) {
+				assert.EqualValues(
+					t,
+					result,
+					map[string]Dimensions{
+						"static": {X0: 0, X1: 9, Y0: 0, Y1: 9},
+						// not sure if X0: 10, X1: 9 makes any sense, but testing this in the
+						// actual GUI it seems harmless
+						"dynamic1": {X0: 10, X1: 9, Y0: 0, Y1: 9},
+						"dynamic2": {X0: 10, X1: 9, Y0: 0, Y1: 9},
+					},
+				)
+			},
+		},
 	}
 
 	for _, s := range scenarios {