UNIT_FACTION fires on the faction template's own edge (#858)

A target whose faction template the server swaps live (35 to 14, neither naming a faction group) kept its friendly plate colour: `UNIT_FACTION` fired only when the pvp, FFA, faction-group or tapped state moved.

The reference's per-field watch fires `UNIT_FACTION` on any change of `UNIT_FIELD_FACTIONTEMPLATE`, as it fires `UNIT_FLAGS` for that field. `fire_transitions` now also fires it on the faction template's edge.

Test: `a_live_faction_template_change_recolours_the_target_plate`.

From #855 by @kalistoking, landed here because the fork refuses maintainer pushes.

Co-authored-by: kalistoking <148718830+kalistoking@users.noreply.github.com>

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/benilla-app/src/ui_script/unit_frame_tests.rs

@@ -958,6 +958,57 @@ fn an_exalted_npc_target_reads_revered_and_its_plate_is_green() {
     }
 }
 
+/// A target whose faction template the server changes live recolours its plate: template 35
+/// (friendly) to 14 (hostile) names no side either way, so only the template's own edge fires
+/// `UNIT_FACTION`. No edge, or another unit's, leaves the plate as it was.
+#[test]
+fn a_live_faction_template_change_recolours_the_target_plate() {
+    benilla_formats::wow_data_or_skip!();
+    use crate::net::FieldEdges;
+    use benilla_protocol::field::FIELD_UNIT_FACTIONTEMPLATE;
+
+    const MOB: u64 = 0xF130_0000_3796_0001;
+    let mut s = UiScript::new().unwrap();
+    s.set_screen_size(1024.0, 768.0);
+    load_unit_frames(&s);
+    let mob = |reaction: u8| UnitState {
+        exists: true,
+        has_object: true,
+        guid: MOB,
+        name: Some("Pusillin".into()),
+        health: 100,
+        max_health: 100,
+        level: 58,
+        reaction,
+        can_attack: reaction < 4,
+        ..UnitState::default()
+    };
+    let is_green = |c: [f32; 4]| c[0].abs() < 1e-6 && (c[1] - 1.0).abs() < 1e-6;
+    let is_red = |c: [f32; 4]| (c[0] - 1.0).abs() < 1e-6 && c[1].abs() < 1e-6;
+
+    let friendly = mob(5);
+    s.set_unit("target", Some(friendly.clone()));
+    s.fire_event("PLAYER_TARGET_CHANGED", vec![]);
+    let before = plate_color(&mut s);
+    assert!(is_green(before), "template 35 reads green, got {before:?}");
+
+    let hostile = mob(2);
+    s.set_unit("target", Some(hostile.clone()));
+    let fire = |s: &mut UiScript, prev: &UnitState, edges: &[(u64, u16)]| {
+        crate::ui_unit::fire_transitions(s, "target", Some(prev), &hostile, &FieldEdges::of(edges));
+    };
+    fire(&mut s, &friendly, &[]);
+    let stale = plate_color(&mut s);
+    assert!(is_green(stale), "no edge, no repaint, got {stale:?}");
+    fire(&mut s, &hostile, &[(MOB + 1, FIELD_UNIT_FACTIONTEMPLATE)]);
+    let other = plate_color(&mut s);
+    assert!(is_green(other), "another unit's edge, got {other:?}");
+    fire(&mut s, &hostile, &[(MOB, FIELD_UNIT_FACTIONTEMPLATE)]);
+    let after = plate_color(&mut s);
+    assert!(is_red(after), "template 14 reads red, got {after:?}");
+    assert!(s.errors().is_empty(), "script errors: {:?}", s.errors());
+}
+
 /// Stock `TargetFrame_CheckClassification` (`TargetFrame.lua:205-218`), asserted on the drawn
 /// quads: elite, rare-elite and world boss share the Elite art (1.12 ships no rare-elite border),
 /// and `UNIT_CLASSIFICATION_CHANGED` alone repaints it.

crates/benilla-app/src/ui_unit.rs

@@ -1185,11 +1185,19 @@ pub(crate) fn fire_transitions(
     }
     // `UNIT_FACTION`, the PvP-icon repaint, on the fields the icon reads and on the tapped bit: the
     // reference's dynamic-flags watcher (`0x600440`) fires event 29 on bit `0x4` (`0x6005a1` →
-    // `0x6005b0`) and has no arm for `0x8`.
-    if prev.is_none_or(|p| {
-        (p.pvp, p.is_pvp_ffa, &p.faction_group, p.tapped)
-            != (cur.pvp, cur.is_pvp_ffa, &cur.faction_group, cur.tapped)
-    }) {
+    // `0x6005b0`) and has no arm for `0x8`. Also on any change of `UNIT_FIELD_FACTIONTEMPLATE`, the
+    // watch bridge's id 29 (`0x51bbb0`, as for `UNIT_FLAGS` above): a template swap between two
+    // that name no faction group moves nothing in the tuple, yet changes the reaction.
+    let template_moved = edges.moved(
+        cur.guid,
+        benilla_protocol::field::FIELD_UNIT_FACTIONTEMPLATE,
+    );
+    if template_moved
+        || prev.is_none_or(|p| {
+            (p.pvp, p.is_pvp_ffa, &p.faction_group, p.tapped)
+                != (cur.pvp, cur.is_pvp_ffa, &cur.faction_group, cur.tapped)
+        })
+    {
         script.fire_event("UNIT_FACTION", vec![tok()]);
     }
 }