Store graphics: Scale sprites only once

Prepare downscaled sprites once instead of doing it on every frame.

Note that we do this lazily in `StartStore` rather than
`SetupTownStores` because we need the palette blending table to be
available when downscaling.

Source/cursor.cpp

@@ -28,6 +28,9 @@
 #include "track.h"
 #include "utils/attributes.h"
 #include "utils/language.h"
+#include "utils/sdl_bilinear_scale.hpp"
+#include "utils/static_vector.hpp"
+#include "utils/surface_to_clx.hpp"
 #include "utils/utf8.hpp"
 
 namespace devilution {
@@ -108,6 +111,9 @@ const uint16_t InvItemHeight2[InvItems2Size] = {
 	// clang-format on
 };
 
+constexpr size_t NumInvItems = InvItems1Size + InvItems2Size - static_cast<size_t>(CURSOR_FIRSTITEM);
+StaticVector<OwnedClxSpriteList, NumInvItems> *HalfSizeItemSprites;
+
 } // namespace
 
 /** Current highlighted monster */
@@ -153,6 +159,11 @@ ClxSprite GetInvItemSprite(int cursId)
 	return (*pCursCels2)[cursId - InvItems1Size - 1];
 }
 
+size_t GetNumInvItems()
+{
+	return InvItems1Size + InvItems2Size;
+}
+
 Size GetInvItemSize(int cursId)
 {
 	const int i = cursId - 1;
@@ -161,6 +172,36 @@ Size GetInvItemSize(int cursId)
 	return { InvItemWidth1[i], InvItemHeight1[i] };
 }
 
+ClxSprite GetHalfSizeItemSprite(int cursId)
+{
+	return (*HalfSizeItemSprites)[cursId][0];
+}
+
+void CreateHalfSizeItemSprites()
+{
+	if (HalfSizeItemSprites != nullptr)
+		return;
+	HalfSizeItemSprites = new StaticVector<OwnedClxSpriteList, NumInvItems>;
+	for (size_t i = 0; i < NumInvItems; ++i) {
+		const ClxSprite itemSprite = GetInvItemSprite(static_cast<int>(CURSOR_FIRSTITEM) + static_cast<int>(i));
+		const OwnedSurface itemSurface(itemSprite.width(), itemSprite.height());
+		SDL_FillRect(itemSurface.surface, nullptr, 1);
+		ClxDraw(itemSurface, { 0, itemSurface.h() }, itemSprite);
+
+		const OwnedSurface halfSurface(itemSurface.w() / 2, itemSurface.h() / 2);
+		BilinearDownscaleByHalf8(itemSurface.surface, paletteTransparencyLookup, halfSurface.surface, 1);
+		HalfSizeItemSprites->emplace_back(SurfaceToClx(halfSurface, 1, 1));
+	}
+}
+
+void FreeHalfSizeItemSprites()
+{
+	if (HalfSizeItemSprites != nullptr) {
+		delete HalfSizeItemSprites;
+		HalfSizeItemSprites = nullptr;
+	}
+}
+
 void DrawItem(const Item &item, const Surface &out, Point position, ClxSprite clx)
 {
 	const bool usable = item._iStatFlag;

Source/cursor.h

@@ -67,6 +67,10 @@ void DrawItem(const Item &item, const Surface &out, Point position, ClxSprite cl
 /** Returns the sprite for the given inventory index. */
 ClxSprite GetInvItemSprite(int cursId);
 
+ClxSprite GetHalfSizeItemSprite(int cursId);
+void CreateHalfSizeItemSprites();
+void FreeHalfSizeItemSprites();
+
 /** Returns the width and height for an inventory index. */
 Size GetInvItemSize(int cursId);
 

Source/stores.cpp

@@ -24,10 +24,8 @@
 #include "towners.h"
 #include "utils/format_int.hpp"
 #include "utils/language.h"
-#include "utils/sdl_bilinear_scale.hpp"
 #include "utils/stdcompat/string_view.hpp"
 #include "utils/str_cat.hpp"
-#include "utils/surface_to_clx.hpp"
 #include "utils/utf8.hpp"
 
 namespace devilution {
@@ -2257,6 +2255,9 @@ void SetupTownStores()
 
 void FreeStoreMem()
 {
+	if (*sgOptions.Graphics.showItemGraphicsInStores) {
+		FreeHalfSizeItemSprites();
+	}
 	stextflag = STORE_NONE;
 	for (STextStruct &entry : stext) {
 		entry.text.clear();
@@ -2287,17 +2288,11 @@ void PrintSString(const Surface &out, int margin, int line, string_view text, Ui
 	const int halfCursWidth = cursWidth / 2;
 
 	if (*sgOptions.Graphics.showItemGraphicsInStores && cursId >= 0) {
-		const ClxSprite itemSprite = GetInvItemSprite(static_cast<int>(CURSOR_FIRSTITEM) + cursId);
-		const OwnedSurface itemSurface(itemSprite.width(), itemSprite.height());
-		SDL_FillRect(itemSurface.surface, nullptr, 1);
-		ClxDraw(itemSurface, { 0, itemSurface.h() }, itemSprite);
-
-		const OwnedSurface halfSurface(itemSurface.w() / 2, itemSurface.h() / 2);
-		BilinearDownscaleByHalf8(itemSurface.surface, paletteTransparencyLookup, halfSurface.surface, 1);
-
-		const Displacement spriteOffset { (halfCursWidth - halfSurface.w()) / 2, (TextHeight() * 3 + halfSurface.h()) / 2 };
-		const OwnedClxSpriteList halfSprite = SurfaceToClx(halfSurface, 1, 1);
-		ClxDraw(out, rect.position + spriteOffset, halfSprite[0]);
+		const ClxSprite halfSprite = GetHalfSizeItemSprite(cursId);
+		ClxDraw(out,
+		    { rect.position.x + (halfCursWidth - halfSprite.width()) / 2,
+		        rect.position.y + (TextHeight() * 3 + halfSprite.height()) / 2 },
+		    halfSprite);
 	}
 
 	if (*sgOptions.Graphics.showItemGraphicsInStores && cursIndent) {
@@ -2354,6 +2349,9 @@ void ClearSText(int s, int e)
 
 void StartStore(talk_id s)
 {
+	if (*sgOptions.Graphics.showItemGraphicsInStores) {
+		CreateHalfSizeItemSprites();
+	}
 	sbookflag = false;
 	CloseInventory();
 	chrflag = false;