Using a CollapsingHeader/treenode inside a node, it's ui goes out of bounds of the node;

[bigbigzxl]

1. Using a CollapsingHeader/treenode inside a node, it's ui goes out of bounds of the node;

ImNodes::BeginNode(node.id);
{
    ImNodes::BeginStaticAttribute(node.ui.add.rhs);
    if (ImGui::CollapsingHeader("Filtering"))
    {
        ImGui::BulletText(
            "Sections below are demonstrating many aspects of the library.");
        ImGui::TextUnformatted("result");
    }
    ImNodes::EndStaticAttribute();
}
ImNodes::EndNode();

[hiroMTB]

This can be solved by a quick dirty hack like below.

imnodes.cpp

int EndNode()
{
   ...

    ImNodeData& node = editor.Nodes.Pool[GImNodes->CurrentNodeIdx];
    node.Rect = GetItemRect();
   
    int width = node.Rect.GetWidth();
    
   ...    
    return width;
}

// your node implementation

#include <imgui_internal.h>


void drawMyNode(){
  // start your node
  ImNodes::BeginNode(id);
     
  ImGuiWindow* window = ImGui::GetCurrentWindow();
  ImRect backup = window->WorkRect;
  
  static nodeWidth = 100;  // default 100px
  
  // Here we overwrite window value
  window->WorkRect.Min.x = window->DC.CursorPos.x;
  window->WorkRect.Max.x = window->WorkRect.Min.x + nodeWidth;
      
  if(ImGui::CollapsingHeader("My Header", ImGuiTreeNodeFlags_DefaultOpen))
  {
       ImGui::Text("ABC");
  }
  window->WorkRect = backup;  // recover correct value
  ImNodes::EndNode();
  
  nodeWidth = w;
}

What we do with above code is ...

1. first render node with 100px (or whatever) default width as we don't know the actual width
2. modified version of EndNode() returns node width
3. Overwrite window.WorkRect and put it back after CollapsingHeader.

Negative points are ...

• 1 frame delay
• dirty
• it could break imgui internal window related code as we overwrite WorkRect in a bad manner
• without ImGuiTreeNodeFlags_DefaultOpen, it calculate wrong width