Some patches for a smoother integration of imgui-node-editor and imgui

[pthom]

Hello @thedmd,

Many thanks for your wonderful library!

During the development of Dear ImGui Bundle, I applied a series of patches to imgui-node-editor and imgui, to make their integration smoother. Since they require modifications on both imgui and imgui-node-editor, proposing a PR is not straightforward.

However, since they might be useful, I took the time to group them here in this issue, in the hope of being helpful.

Demo

Video demo:

Untitled13.mov

You can also test it live on this webasm demo

Handle node width in separators:

Thanks to this patch, ImGui::SeparatorText(), ImGui::Separator(), and ImGui::CollapsingHeader() can use the actual node width. It was proposed here

Handle Popups:

@lukaasm proposed a patch here, which solves many issues with popups in the node editor (by automatically suspending the canvas, and placing popups correctly).

Example implementation for this patch:

• inside imgui-node-editor
• inside imgui

With this patch, ImGui::ColorEdit, ImGui::Begin/EndCombo will work correctly inside a node.

Warn users if using BeginChild / EndChild:

imgui-node-editor remains incompatible with ImGui::BeginChild() and ImGui::EndChild().

Below is the list of ImGui widgets which are concerned (because they use BeginChild/EndChild):

• ImGui::InputTextMultiline()
• ImGui::BeginListbox() and ImGui::EndListbox()
• ImGui::BeginChild() and ImGui::EndChild()

We can warn the developer whenever they use these functions inside a node:

• patch inside imgui
• patch inside imgui-node-editor

Handle InputTextMultiline

By default InputTextMultiline uses a child window, which is not compatible with the node editor.
An additional patch adapts its behavior, by showing a preview within a single line text input,
followed by a "..." button which triggers a popup with the full text edition.

To apply this, two patches are required:

• inside imgui-node-editor: A patch on top of @lukaasm's patch:
  we need to handle the "depth" of call to ImGui::Begin/End (only the first call should trigger):
  it is available here
• inside imgui: A patch for InputTextMultiline is available here