brush panel folding

src/node.cpp

@@ -445,6 +445,7 @@ Node&& Node::operator=(Node&& o)
 Node::Node()
 {
     y_node = YGNodeNew();
+    y_placeholder = nullptr;
 }
 
 Node::Node(Node&& o)
@@ -493,6 +494,8 @@ Node::~Node()
     m_children.clear();
     if (y_node)
         YGNodeFree(y_node);
+    if (y_placeholder)
+        YGNodeFree(y_placeholder);
 }
 
 void Node::SetWidth(float value)
@@ -629,6 +632,39 @@ void Node::SetRTL(YGDirection dir)
     YGNodeStyleSetDirection(y_node, dir);
 }
 
+void Node::SetVisibility(bool visible)
+{
+    if (m_display && !visible)
+    {
+        // hide
+        int idx = parent->get_child_index(this);
+        YGNodeRemoveChild(parent->y_node, y_node);
+        y_placeholder = YGNodeNew();
+        YGNodeInsertChild(parent->y_node, y_placeholder, idx);
+    }
+    else if (!m_display && visible)
+    {
+        int count = YGNodeGetChildCount(parent->y_node);
+        for (int i = 0; i < count; i++)
+        {
+            if (YGNodeGetChild(parent->y_node, i) == y_placeholder)
+            {
+                YGNodeRemoveChild(parent->y_node, y_placeholder);
+                YGNodeInsertChild(parent->y_node, y_node, i);
+                YGNodeFree(y_placeholder);
+                y_placeholder = nullptr;
+                break;
+            }
+        }
+    }
+    m_display = visible;
+}
+
+void Node::ToggleVisibility()
+{
+    SetVisibility(!m_display);
+}
+
 glm::vec2 Node::GetPosition()
 {
     return{ YGNodeLayoutGetLeft(y_node), YGNodeLayoutGetTop(y_node) };