shithub: rgbds

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Implement `-m`

Though none of the code involved has been tested in any capacity yet, lol

--- a/src/gfx/convert.cpp

+++ b/src/gfx/convert.cpp

@@ -674,14 +674,43 @@

 		VHFLIP,

 	};

 	MatchType tryMatching(TileData const &other) const {

-		if (std::equal(_data.begin(), _data.end(), other._data.begin()))

+		// Check for strict equality first, as that can typically be optimized, and it allows

+		// hoisting the mirroring check out of the loop

+		if (_data == other._data) {

 			return MatchType::EXACT;

+		}

-		if (options.allowMirroring) {

-			// TODO

+		if (!options.allowMirroring) {

+			return MatchType::NOPE;

 		}

-		return MatchType::NOPE;

+		// Check if we have horizontal mirroring, which scans the array forward again

+		if (std::equal(_data.begin(), _data.end(), other._data.begin(),

+		               [](uint8_t lhs, uint8_t rhs) { return lhs == flip(rhs); })) {

+			return MatchType::HFLIP;

+		}

+

+		// Check if we have vertical or vertical+horizontal mirroring, for which we have to read

+		// bitplane *pairs*  backwards

+		bool hasVFlip = true, hasVHFlip = true;

+		for (uint8_t i = 0; i < _data.size(); ++i) {

+			// Flip the bottom bit to get the corresponding row's bitplane 0/1

+			// (This works because the array size is even)

+			uint8_t lhs = _data[i], rhs = other._data[(15 - i) ^ 1];

+			if (lhs != rhs) {

+				hasVFlip = false;

+			}

+			if (lhs != flip(rhs)) {

+				hasVHFlip = false;

+			}

+			if (!hasVFlip && !hasVHFlip) {

+				return MatchType::NOPE; // If both have been eliminated, all hope is lost!

+			}

+		}

+

+		// If we have both (i.e. we have symmetry), default to vflip only

+		assert(hasVFlip || hasVHFlip);

+		return hasVFlip ? MatchType::VFLIP : MatchType::VHFLIP;

 	}

 	friend bool operator==(TileData const &lhs, TileData const &rhs) {

 		return lhs.tryMatching(rhs) != MatchType::NOPE;

@@ -745,7 +774,6 @@

 		iter->xFlip = matchType == TileData::HFLIP || matchType == TileData::VHFLIP;

 		iter->yFlip = matchType == TileData::VFLIP || matchType == TileData::VHFLIP;

-		assert(tileID < 1 << 10);

 		iter->tileID = tileID;

 		++iter;