fix(a380x/fcu): pre-sel not recognising baro unit change (#9164)

Co-authored-by: Saschl <[email protected]>
Co-authored-by: alepouna <[email protected]>

.github/CHANGELOG.md

@@ -8,7 +8,8 @@
 ## 0.13.0
 
 1. [GENERAL] Fixed issue in C++ WASM Framework that caused performance degradation in some WASM modules - @frankkopp (Frank Kopp)
-1. [FCU] Fixed auto-initialisation of baro unit - @tracernz (Mike)
+1. [A380X/FCU] Fixed auto-initialisation of baro unit - @tracernz (Mike)
+1. [A380X/FCU] Fix baro-preselect not recognising baro unit changes - @tracernz (Mike)
 
 ## 0.12.0
 

fbw-a380x/src/systems/instruments/src/FCU/Managers/BaroManager.ts

@@ -1,7 +1,7 @@
 // Copyright (c) 2023-2024 FlyByWire Simulations
 // SPDX-License-Identifier: GPL-3.0
 
-import { EventBus, HEvent, Instrument, KeyEventManager, Subject, UnitType } from '@microsoft/msfs-sdk';
+import { EventBus, HEvent, Instrument, KeyEventManager, MathUtils, Subject, UnitType } from '@microsoft/msfs-sdk';
 
 export type BaroMode = ReturnType<typeof Simplane.getPressureSelectedMode>;
 export type BaroUnit = ReturnType<typeof Simplane.getPressureSelectedUnits>;
@@ -56,7 +56,7 @@ export class BaroManager implements Instrument {
       this.publisher.pub(this.modeEventKey, v);
     }, true);
 
-    this.unit.sub((v) => this.publisher.pub(this.unitEventKey, v), true);
+    this.unit.sub(this.onBaroUnitChanged.bind(this), true);
 
     this.correction.sub((v) => this.publisher.pub(this.correctionEventKey, v));
 
@@ -75,6 +75,21 @@ export class BaroManager implements Instrument {
     }
   }
 
+  private onBaroUnitChanged(newUnit: BaroUnit): void {
+    this.publisher.pub(this.unitEventKey, newUnit);
+
+    if (this.mode.get() === 'STD') {
+      // we need to change the unit of the pre-selected value
+      const correction = this.correction.get();
+      const isCorrectionInHg = correction < 100;
+      if (newUnit === 'inches of mercury' && !isCorrectionInHg) {
+        this.correction.set(MathUtils.round(UnitType.IN_HG.convertFrom(correction, UnitType.HPA), 0.01));
+      } else if (newUnit === 'millibar' && isCorrectionInHg) {
+        this.correction.set(MathUtils.round(UnitType.HPA.convertFrom(correction, UnitType.IN_HG), 1));
+      }
+    }
+  }
+
   private onHEvent(event: string): void {
     if (this.mode.get() !== 'STD') {
       return;