Node with title bar gets expanded infinitely

[tim-tim707]

I'm trying to make the default examples work. Here is my main loop:

void main_loop(App &app) {
    ImGui::Begin("node editor");
    ImNodes::BeginNodeEditor();

    const int hardcoded_node_id = 1;

    ImNodes::BeginNode(hardcoded_node_id + 1);

    ImNodes::BeginNodeTitleBar();
    ImGui::TextUnformatted("node");
    ImNodes::EndNodeTitleBar();

    ImNodes::EndNode();

    ImNodes::EndNodeEditor();
    ImGui::End();
}
// Elsewhere:
    while (glfwWindowShouldClose(window) != GLFW_TRUE) {
        glfwPollEvents();
        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplGlfw_NewFrame();
        ImGui::NewFrame();

        main_loop(app);

        ImGui::Render();
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

        glfwSwapBuffers(window);
    }

For some reason, the node rectangle gets expanded every loop by the padding value at

ImNodes::EndNode(); -> node.Rect.Expand(node.LayoutStyle.Padding); -> Rect gets 8 pixel added to Max.x every loop (but not Max.y)

I don't really understand why it is doing this. Should I create a context and destroy it every frame ? I'm not doing it for ImGui and the examples do not seem to do it as well.

ImGui version 1.19.1
imnodes from branch master commit b2ec254

[tim-tim707]

Seems that this works properly:

    ImGui::Begin("node editor");
    ImNodes::BeginNodeEditor();

    ImNodes::BeginNode(1);

    ImNodes::BeginNodeTitleBar();
    ImGui::TextUnformatted("node");
    ImNodes::EndNodeTitleBar();

    ImNodes::BeginOutputAttribute(2);
    ImGui::TextUnformatted("output pin");
    ImNodes::EndOutputAttribute();

    ImNodes::EndNode();

    ImNodes::EndNodeEditor();
    ImGui::End();

But this does not (expand infinitely):

    ImGui::Begin("node editor");
    ImNodes::BeginNodeEditor();

    ImNodes::BeginNode(1);

    ImNodes::BeginNodeTitleBar();
    ImGui::TextUnformatted("node");
    ImNodes::EndNodeTitleBar();

    // Removed the BeginOutputAttribute and EndOutputAttribute calls

    ImNodes::EndNode();

    ImNodes::EndNodeEditor();
    ImGui::End();

[donovan-TGC]

I experienced something similar. I found that if I don't layout any widgets or attributes after EndNodeTitleBar() that the width increases by 8 pixels on ever layout frame.

My solution (workaround) was to emit an ImGui::Dummy(0,0) between the EndNodeTitleBar() and EndNode() calls.

[gbbnfhb]

I believe the root cause is in the GetNodeTitleRect function:
`
inline ImRect GetNodeTitleRect(const ImNodeData& node)
{
// 1. Get the rectangle occupied by the title bar's content (e.g., text),
// and expand it slightly by adding padding.
ImRect expanded_title_rect = node.TitleBarContentRect;
expanded_title_rect.Expand(node.LayoutStyle.Padding);

// 2. Calculate and return the new title bar rectangle.
return ImRect(
    expanded_title_rect.Min,
    expanded_title_rect.Min + ImVec2(node.Rect.GetWidth(), 0.f) +
        ImVec2(0.f, expanded_title_rect.GetHeight()));

}`
The problem is: This implementation creates a feedback loop. The layout inside the title bar expands to fit the node's width, but the node's width is also being recalculated based on the content's width. As a result, if the function is called repeatedly, the node's width keeps growing.

---

I changed it to ignore the content's width for sizing and only use its height, like this:
`
inline ImRect GetNodeTitleRect(const ImNodeData& node)
{
// Get the rectangle for the content.
ImRect expanded_title_rect = node.TitleBarContentRect;
// Add vertical padding.
expanded_title_rect.Expand(node.LayoutStyle.Padding);

// Calculate and return the new title bar rectangle.
return ImRect(
    // Use the content's top-left for the top-left coordinate.
    expanded_title_rect.Min,
    // The width (X) ignores the content's width and always uses the node's current width.
    // The height (Y) uses the content's height to allow for collapsing/expanding.
    expanded_title_rect.Min + ImVec2(node.Rect.GetWidth(), expanded_title_rect.GetHeight())
);

}
`

[gbbnfhb]

This leads to another question: where is the node's width originally determined? Tracing this back reveals a different potential issue with the following function
inline ImRect GetItemRect() { return ImRect(ImGui::GetItemRectMin(), ImGui::GetItemRectMax()); }
While this appears harmless, it's important to note that this function returns the rect of the immediately preceding ImGui item, not necessarily the rect of the entire node.