From ca1af5a5051428f3228f4aafae5c781adde78e51 Mon Sep 17 00:00:00 2001
From: tobspr <tobias.springer1@googlemail.com>
Date: Mon, 7 Dec 2020 13:04:58 +0100
Subject: [PATCH] Allow cycling backwards, closes #790

---
 src/js/changelog.js                   |  1 +
 src/js/game/hud/parts/base_toolbar.js | 12 ++++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/src/js/changelog.js b/src/js/changelog.js
index b13ccf31..76498a7c 100644
--- a/src/js/changelog.js
+++ b/src/js/changelog.js
@@ -5,6 +5,7 @@ export const CHANGELOG = [
         entries: [
             "Added the ability to edit constant signals by left clicking them",
             "You can now add markers in the wire layer (partially by daanbreur)",
+            "Allow to cycle backwards in the toolbar with SHIFT + Tab (idea by emeraldblock)",
         ],
     },
     {
diff --git a/src/js/game/hud/parts/base_toolbar.js b/src/js/game/hud/parts/base_toolbar.js
index a0e2a49f..b3f5abfc 100644
--- a/src/js/game/hud/parts/base_toolbar.js
+++ b/src/js/game/hud/parts/base_toolbar.js
@@ -1,6 +1,6 @@
 import { gMetaBuildingRegistry } from "../../../core/global_registries";
-import { Signal, STOP_PROPAGATION } from "../../../core/signal";
-import { makeDiv } from "../../../core/utils";
+import { STOP_PROPAGATION } from "../../../core/signal";
+import { makeDiv, safeModulo } from "../../../core/utils";
 import { KEYMAPPINGS } from "../../key_action_mapper";
 import { MetaBuilding } from "../../meta_building";
 import { GameRoot } from "../../root";
@@ -161,8 +161,12 @@ export class HUDBaseToolbar extends BaseHUDPart {
 
         let newBuildingFound = false;
         let newIndex = this.lastSelectedIndex;
-        for (let i = 0; i < this.primaryBuildings.length; ++i, ++newIndex) {
-            newIndex %= this.primaryBuildings.length;
+        const direction = this.root.keyMapper.getBinding(KEYMAPPINGS.placement.rotateInverseModifier).pressed
+            ? -1
+            : 1;
+
+        for (let i = 0; i <= this.primaryBuildings.length; ++i) {
+            newIndex = safeModulo(newIndex + direction, this.primaryBuildings.length);
             const metaBuilding = gMetaBuildingRegistry.findByClass(this.primaryBuildings[newIndex]);
             const handle = this.buildingHandles[metaBuilding.id];
             if (!handle.selected && handle.unlocked) {