Prevent duplicate metatile pastes in the tileset editor

include/core/metatile.h

@@ -54,4 +54,18 @@ public:
     static int getAttributesSize(BaseGameVersion version);
 };
 
+inline bool operator==(const Metatile &a, const Metatile &b) {
+    return a.behavior         == b.behavior &&
+           a.layerType        == b.layerType &&
+           a.encounterType    == b.encounterType &&
+           a.terrainType      == b.terrainType &&
+           a.unusedAttributes == b.unusedAttributes &&
+           a.label            == b.label &&
+           a.tiles            == b.tiles;
+}
+
+inline bool operator!=(const Metatile &a, const Metatile &b) {
+    return !(operator==(a, b));
+}
+
 #endif // METATILE_H

include/core/tile.h

@@ -22,4 +22,15 @@ public:
     static int getIndexInTileset(int);
 };
 
+inline bool operator==(const Tile &a, const Tile &b) {
+    return a.tileId  == b.tileId &&
+           a.xflip   == b.xflip &&
+           a.yflip   == b.yflip &&
+           a.palette == b.palette;
+}
+
+inline bool operator!=(const Tile &a, const Tile &b) {
+    return !(operator==(a, b));
+}
+
 #endif // TILE_H

src/ui/tileseteditor.cpp

@@ -815,7 +815,7 @@ void TilesetEditor::onPaletteEditorChangedPalette(int paletteId) {
 bool TilesetEditor::replaceMetatile(uint16_t metatileId, Metatile * src)
 {
     Metatile * dest = Tileset::getMetatile(metatileId, this->primaryTileset, this->secondaryTileset);
-    if (!dest || !src)
+    if (!dest || !src || *dest == *src)
         return false;
 
     this->metatile = dest;