From 6c39def2870460b3321711cb8981bb20d549b696 Mon Sep 17 00:00:00 2001
From: Peter Nelson <peter1138@openttd.org>
Date: Wed, 20 May 2026 21:38:26 +0100
Subject: [PATCH] Codechange: use EnumIndexArray for ZoomLevel-indexed arrays

---
 src/sound.cpp                     |  9 +++++----
 src/spriteloader/spriteloader.hpp | 10 +++++-----
 src/viewport.cpp                  | 12 ++++++------
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/src/sound.cpp b/src/sound.cpp
index 2a2556b50b..b9c7908f9e 100644
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -120,9 +120,10 @@ static void StartSound(SoundID sound_id, float pan, uint volume)
 	MxActivateChannel(mc);
 }
 
-
-static const uint8_t _vol_factor_by_zoom[] = {255, 255, 255, 190, 134, 87};
-static_assert(lengthof(_vol_factor_by_zoom) == to_underlying(ZoomLevel::End));
+/** Volume scaling for each zoom level. */
+static constexpr EnumIndexArray<uint8_t, ZoomLevel, ZoomLevel::End> _vol_factor_by_zoom{
+	255, 255, 255, 190, 134, 8
+};
 
 static const uint8_t _sound_base_vol[] = {
 	128,  90, 128, 128, 128, 128, 128, 128,
@@ -215,7 +216,7 @@ static void SndPlayScreenCoordFx(SoundID sound, int left, int right, int top, in
 			StartSound(
 				sound,
 				panning,
-				_vol_factor_by_zoom[to_underlying(vp.zoom)]
+				_vol_factor_by_zoom[vp.zoom]
 			);
 			return;
 		}
diff --git a/src/spriteloader/spriteloader.hpp b/src/spriteloader/spriteloader.hpp
index a6a0de255f..4034064cfe 100644
--- a/src/spriteloader/spriteloader.hpp
+++ b/src/spriteloader/spriteloader.hpp
@@ -32,13 +32,13 @@ using SpriteComponents = EnumBitSet<SpriteComponent, uint8_t, SpriteComponent::E
  */
 template <class T>
 class SpriteCollMap {
-	std::array<T, to_underlying(ZoomLevel::End)> data{};
+	EnumIndexArray<T, ZoomLevel, ZoomLevel::End> data{};
 public:
-	inline constexpr T &operator[](const ZoomLevel &zoom) { return this->data[to_underlying(zoom)]; }
-	inline constexpr const T &operator[](const ZoomLevel &zoom) const { return this->data[to_underlying(zoom)]; }
+	inline constexpr T &operator[](const ZoomLevel &zoom) { return this->data[zoom]; }
+	inline constexpr const T &operator[](const ZoomLevel &zoom) const { return this->data[zoom]; }
 
-	T &Root() { return this->data[to_underlying(ZoomLevel::Min)]; }
-	const T &Root() const { return this->data[to_underlying(ZoomLevel::Min)]; }
+	T &Root() { return this->data[ZoomLevel::Min]; }
+	const T &Root() const { return this->data[ZoomLevel::Min]; }
 };
 
 /** Interface for the loader of our sprites. */
diff --git a/src/viewport.cpp b/src/viewport.cpp
index 79c4540f21..2c5ae31761 100644
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -1556,17 +1556,17 @@ void ViewportSign::UpdatePosition(int center, int top, std::string_view str, std
  */
 void ViewportSign::MarkDirty(ZoomLevel maxzoom) const
 {
-	Rect zoomlevels[to_underlying(ZoomLevel::End)];
+	EnumIndexArray<Rect, ZoomLevel, ZoomLevel::End> zoomlevels;
 
 	/* We don't know which size will be drawn, so mark the largest area dirty. */
 	const uint half_width = std::max(this->width_normal, this->width_small) / 2 + 1;
 	const uint height = WidgetDimensions::scaled.fullbevel.top + std::max(GetCharacterHeight(FontSize::Normal), GetCharacterHeight(FontSize::Small)) + WidgetDimensions::scaled.fullbevel.bottom + 1;
 
 	for (ZoomLevel zoom = ZoomLevel::Begin; zoom != ZoomLevel::End; zoom++) {
-		zoomlevels[to_underlying(zoom)].left = this->center - ScaleByZoom(half_width, zoom);
-		zoomlevels[to_underlying(zoom)].top = this->top - ScaleByZoom(1, zoom);
-		zoomlevels[to_underlying(zoom)].right = this->center + ScaleByZoom(half_width, zoom);
-		zoomlevels[to_underlying(zoom)].bottom = this->top + ScaleByZoom(height, zoom);
+		zoomlevels[zoom].left = this->center - ScaleByZoom(half_width, zoom);
+		zoomlevels[zoom].top = this->top - ScaleByZoom(1, zoom);
+		zoomlevels[zoom].right = this->center + ScaleByZoom(half_width, zoom);
+		zoomlevels[zoom].bottom = this->top + ScaleByZoom(height, zoom);
 	}
 
 	for (const Window *w : Window::Iterate()) {
@@ -1575,7 +1575,7 @@ void ViewportSign::MarkDirty(ZoomLevel maxzoom) const
 		Viewport &vp = *w->viewport;
 		if (vp.zoom <= maxzoom) {
 			assert(vp.width != 0);
-			Rect &zl = zoomlevels[to_underlying(vp.zoom)];
+			Rect &zl = zoomlevels[vp.zoom];
 			MarkViewportDirty(vp, zl.left, zl.top, zl.right, zl.bottom);
 		}
 	}