[nostalgia/core/opengl] Implement flip X and flip Y for BG tiles

src/nostalgia/modules/core/include/nostalgia/core/gfx.hpp

@@ -48,8 +48,8 @@ struct BgTile {
 	static constexpr auto TypeVersion = 1;
 	unsigned tileIdx = 0;
 	unsigned palBank = 0;
-	unsigned horizontalFlip = false;
+	unsigned flipX = false;
-	unsigned verticalFlip = false;
+	unsigned flipY = false;
 };
 
 oxModelBegin(BgTile)

src/nostalgia/modules/core/src/gba/gfx.cpp

@@ -289,8 +289,8 @@ void setBgTile(Context&, uint_t bgIdx, int column, int row, BgTile const&tile) n
 	// see Tonc 9.3
 	MEM_BG_MAP[bgIdx][tileIdx] =
 			static_cast<uint16_t>(tile.tileIdx & 0b1'1111'1111) |
-			static_cast<uint16_t>(tile.horizontalFlip << 0xa) |
+			static_cast<uint16_t>(tile.flipX << 0xa) |
-			static_cast<uint16_t>(tile.verticalFlip << 0xb) |
+			static_cast<uint16_t>(tile.flipY << 0xb) |
 			static_cast<uint16_t>(tile.palBank << 0xc);
 }
 

src/nostalgia/modules/core/src/opengl/gfx.cpp

@@ -152,6 +152,8 @@ static void setTileBufferObject(
 		float textureTileIdx,
 		float priority,
 		float palOffset,
+		bool flipX,
+		bool flipY,
 		float *vbo,
 		GLuint *ebo) noexcept {
 	// don't worry, this memcpy gets optimized to something much more ideal
@@ -162,11 +164,15 @@ static void setTileBufferObject(
 	x -= 1.0f;
 	y += 1.0f - ymod;
 	auto const prif = priority * PriorityScale;
+	float const L = flipX ? 1 : 0;
+	float const R = flipX ? 0 : 1;
+	float const T = flipY ? 1 : 0;
+	float const B = flipY ? 0 : 1;
 	ox::Array<float, BgVertexVboLength> const vertices {
-			       x,        y, prif, 0, 1, textureTileIdx, palOffset, // bottom left
+			       x,        y, prif, L, B, textureTileIdx, palOffset, // bottom left
-			x + xmod,        y, prif, 1, 1, textureTileIdx, palOffset, // bottom right
+			x + xmod,        y, prif, R, B, textureTileIdx, palOffset, // bottom right
-			x + xmod, y + ymod, prif, 1, 0, textureTileIdx, palOffset, // top right
+			x + xmod, y + ymod, prif, R, T, textureTileIdx, palOffset, // top right
-			       x, y + ymod, prif, 0, 0, textureTileIdx, palOffset, // top left
+			       x, y + ymod, prif, L, T, textureTileIdx, palOffset, // top left
 	};
 	memcpy(vbo, vertices.data(), sizeof(vertices));
 	ox::Array<GLuint, BgVertexEboLength> const elms {
@@ -197,6 +203,8 @@ static void initBackgroundBufferObjects(glutils::BufferSet &bs) noexcept {
 				0,
 				0,
 				0,
+				false,
+				false,
 				vbo,
 				ebo);
 		}
@@ -612,6 +620,8 @@ void setBgTile(
 			static_cast<float>(tile.tileIdx),
 			bg.priority,
 			static_cast<float>(tile.palBank * 16),
+			tile.flipX,
+			tile.flipY,
 			vbo,
 			ebo);
 	cbb.updated = true;

src/nostalgia/player/app.cpp

@@ -82,7 +82,8 @@ static ox::Error runTest(turbine::Context &tctx) {
 
 [[maybe_unused]]
 static ox::Error runTileSheetSetTest(turbine::Context &tctx) {
-	// this should make the screen display 'ABCDB'
+	// this should make the screen display 'ABCDB', with the A being upside down
+	// and the first B being backwards
 	constexpr ox::FileAddress PaletteAddr = ox::StringLiteral("/Palettes/Charset.npal");
 	oxRequireM(cctx, core::init(tctx));
 	turbine::setApplicationData(tctx, cctx.get());
@@ -103,9 +104,9 @@ static ox::Error runTileSheetSetTest(turbine::Context &tctx) {
 	oxReturnError(core::loadBgPalette(*cctx, 0, ox::StringLiteral("/Palettes/Chester.npal")));
 	oxReturnError(core::loadSpritePalette(*cctx, PaletteAddr));
 	core::setBgStatus(*cctx, 0, true);
-	core::setBgTile(*cctx, 0, 10, 9, 1, bgPalBank);
+	core::setBgTile(*cctx, 0, 10, 9, { .tileIdx = 1, .palBank = bgPalBank, .flipX = 0, .flipY = 1 });
-	core::setBgTile(*cctx, 0, 11, 9, 2, bgPalBank);
+	core::setBgTile(*cctx, 0, 11, 9, { .tileIdx = 2, .palBank = bgPalBank, .flipX = 1, .flipY = 0 });
-	core::setBgTile(*cctx, 0, 13, 9, 4, bgPalBank);
+	core::setBgTile(*cctx, 0, 13, 9, { .tileIdx = 4, .palBank = bgPalBank, .flipX = 0, .flipY = 0 });
 	core::setSprite(*cctx, 16, {
 		.enabled = true,
 		.x = 12 * 8,