PME Treasure

Add a complex Blender widget to a PME Popup Dialog

2 min read

Answer

Some Blender controls are templates rather than simple buttons or properties. If PME reports that a widget cannot be added, use a Custom item and call the corresponding UILayout method through L.

The original example for the screen selector is:

L.template_ID(C.window, "screen", new="screen.new", unlink="screen.delete")

L is PME’s layout object and C is the Blender context.

Steps

  1. Add a Custom item to the Popup Dialog.
  2. Find the widget’s Blender Python UI construction. Enable Blender’s Developer Extras, then use Edit Source from the control’s context menu when available.
  3. Translate the layout call to PME globals. For example, a layout.template_ID(...) call becomes L.template_ID(...).
  4. Use the RNA owner required by the widget in the active Blender context. For the screen selector, the screen property belongs to C.window.
  5. Apply the item and test it in the same kind of editor context as the native control.

The L wrapper forwards standard UILayout methods, including the template_* family, to the underlying Blender layout.

Pitfalls

  • Copying a UI call without its correct data owner is the common failure. C.window, C.space_data, and C.scene are not interchangeable.
  • A template can require a particular editor or region. Test the Popup Dialog where that native context is available.
  • Use keyword arguments for optional operator names, such as new="screen.new"; this keeps the call readable and avoids positional-argument mistakes.
  • A custom layout call must fit PME’s command storage rules. Keep the stored expression on one line; format it across lines only when documenting it.
  • Each template_* call still needs data and context that make sense in its host area.

The source discussion used Blender 2.80. When adapting an older template example, check its signature against the Blender API for the version you use.

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