[Detail Bug] Node editor: multi-receiver group address shows only one link (duplicate LinkId collapse)

Detail Bug Report

https://app.detail.dev/org_62aa40f5-2c23-4914-a665-3bb2068af20e/bugs/bug_06a16365-1787-426d-a796-7084a2e76050

Introduced in bd8a99e7237a73a781580622a800f49ab4652f12 by @kewde on May 13, 2026

Summary

• Context: NodeEditorPanel._compute_visual_links (GA-hidden branch) builds the list of (link_id, start_pin, end_pin) triples that _render_links feeds to imgui_node_editor's ed.link(ed.LinkId(link_id), ...).
• Bug: For group addresses with one sender and multiple receivers, the GA-hidden branch reuses ga.id as the LinkId for every sender×receiver pair. Because imgui_node_editor's Link() reuses the same internal link record when called with a LinkId it has already seen this frame, only one curve (the last-submitted pair) survives — the other assignments are invisible in the editor.
• Actual vs. expected: A 1-sender/3-receiver GA should draw 3 link curves; instead all 3 triplets share LinkId == ga.id and the editor ends up with one link carrying the last (sender, receiver) pair, hiding the other two real assignments.
• Impact: Real assignments are invisible in the node editor (the default view), so users believe certain sensors/receivers are not on the group when they actually are.

Code with Bug

# _compute_visual_links, GA-hidden branch (apps/knx-gui/src/knx_gui/plugins/node_editor/ui.py)
else:
    if len(assignments) < 2:
        continue
    for send_pin in sending_pins:
        for recv_pin in receiving_pins:
            links.append((ga.id, send_pin, recv_pin))   # <-- BUG 🔴 reuses ga.id for every sender×receiver pair

Consumed in _render_links:

def _render_links(self) -> None:
    for ga_id, start_pin, end_pin in self._compute_visual_links():
        match = self._pins_match_quality(start_pin, end_pin)
        color = LINK_LOOSE_COLOR if match == DPTMatch.LOOSE else LINK_COLOR
        ed.link(ed.LinkId(ga_id), ed.PinId(start_pin), ed.PinId(end_pin), color)   # <-- BUG 🔴 duplicate LinkId collapses to one link

Explanation

• In GA-hidden mode, a single GA can yield multiple visual links (one per sender×receiver pair).
• imgui_node_editor identifies links by LinkId. Submitting multiple ed.link() calls with the same LinkId in one frame overwrites/reuses the same internal link record.
• This behavior was reproduced against the real imgui_node_editor bindings: calling ed.link(LinkId(7), ...) three times in one frame with different pin pairs results in ed.get_link_pins(LinkId(7), ...) returning only the last pair, proving the earlier links are lost.

Recommended Fix

Make the visual link ID unique per (sender, receiver) pair in the GA-hidden branch (and maintain a mapping back to the GA for deletion logic). For example, generate a composite link_id based on ga.id plus sender/receiver indices, and keep a visual_link_id -> ga_id map so _handle_link_deletion can still remove the correct GA.

History

This bug was introduced in commit bd8a99e, which refactored link rendering to use _compute_visual_links() and used ga.id as the LinkId for every (send_pin, recv_pin) tuple under a GA. A later commit added unique composite link IDs for the GA-shown mode, but left the GA-hidden (default) branch reusing ga.id.

Start in apps/knx-gui/src/knx_gui/plugins/node_editor/ui.py, reading _compute_visual_links and _render_links to trace how GA-hidden assignments become imgui_node_editor LinkIds. Check _handle_link_deletion as well; done means each sender/receiver pair renders as a distinct curve while deletion still identifies the correct GA.