Add visible = false (may be renamed in the future)

init.lua

@@ -384,9 +384,19 @@ local function expand(box)
         end
     end
 
-    -- Recursively expand
-    for _, node in ipairs(box) do
-        expand(node)
+    -- Recursively expand and remove any invisible nodes
+    for i = #box, 1, -1 do
+        local node = box[i]
+        -- node.visible ~= nil and not node.visible
+        -- WARNING: I'm not sure whether this should be called `visible`, I may
+        -- end up renaming it in the future. Use with caution.
+        if node.visible == false then
+            -- There's no need to try and expand anything inside invisible
+            -- nodes since it won't affect the overall size.
+            table.remove(box, i)
+        else
+            expand(node)
+        end
     end
 end
 
@@ -1004,10 +1014,16 @@ end
 
 function gui.Spacer(def)
     def.type = "container"
+    assert(#def == 0)
+
+    -- Spacers default to expanding
     if def.expand == nil then
         def.expand = true
     end
-    assert(#def == 0)
+
+    -- Prevent an empty container from being added to the resulting form
+    def.visible = false
+
     return def
 end
 

test.lua

@@ -170,4 +170,62 @@ describe("Flow", function()
 
         assert.same(state.callbacks, {btn = func})
     end)
+
+    it("handles visible = false", function()
+        test_render(gui.VBox{
+            min_w = 10, min_h = 10,
+
+            gui.HBox{
+                spacing = 0.5,
+                gui.Box{w = 1, h = 1, color = "red"},
+                gui.Box{w = 1, h = 1, color = "green", visible = false},
+                gui.Box{w = 1, h = 1, color = "blue"},
+            },
+
+            gui.HBox{
+                gui.Box{w = 1, h = 1, color = "red"},
+                gui.Box{w = 1, h = 1, color = "green", visible = false,
+                    expand = true},
+                gui.Box{w = 1, h = 1, color = "blue"},
+            },
+
+            gui.HBox{
+                gui.Box{w = 1, h = 1, color = "grey"},
+                gui.Spacer{},
+                gui.Box{w = 1, h = 1, color = "grey"},
+            },
+
+            gui.HBox{
+                gui.Box{w = 1, h = 1, color = "red", expand = true},
+                gui.Box{w = 1, h = 1, color = "green", visible = false},
+                gui.Box{w = 1, h = 1, color = "blue"},
+            },
+
+            gui.Box{w = 1, h = 1, expand = true},
+        }, [[
+            size[10.6,10.6]
+
+            container[0.3,0.3]
+            box[0,0;1,1;red]
+            box[3,0;1,1;blue]
+            container_end[]
+
+            container[0.3,1.5]
+            box[0,0;1,1;red]
+            box[9,0;1,1;blue]
+            container_end[]
+
+            container[0.3,2.7]
+            box[0,0;1,1;grey]
+            box[9,0;1,1;grey]
+            container_end[]
+
+            container[0.3,3.9]
+            box[0,0;7.6,1;red]
+            box[9,0;1,1;blue]
+            container_end[]
+
+            box[0.3,5.1;10,5.2;]
+        ]])
+    end)
 end)