Do not export BG0 tile descriptors ith the mask bit set if there is only one layer defined

tools/tiled2iigs.js

@@ -197,6 +197,9 @@ function findAnimatedTiles(tileset) {
     return animations;
 }
 
+// Global reference object
+let GLOBALS = {};
+
 /**
  * Command line arguments
  * 
@@ -246,6 +249,13 @@ async function main(argv) {
     // Load up any/all tilesets
     const tileSets = await Promise.all(doc.tilesets.map(tileset => loadTileset(workdir, tileset)));
 
+    // Create a global reference object
+    GLOBALS = {
+        outdir,
+        tileSets,
+        tileLayers
+    };
+
     // Save all of the tilesets
     let bg0TileSet = null;
 
@@ -398,7 +408,7 @@ function convertTileID(tileId, tileset) {
 
     // The tileId starts at one, but the tile set starts at zero.  It's ok when we export,
     // because a special zero tile is inserted, but we have to manually adjust here
-    const mask_bit = !tileset[tileIndex - 1].isSolid;
+    const mask_bit = (!tileset[tileIndex - 1].isSolid) && (GLOBALS.tileLayers.length !== 1);
 
     // Build up a partial set of control bits
     let control_bits = (mask_bit ? GTE_MASK_BIT : 0) + (hflip ? GTE_HFLIP_BIT : 0) + (vflip ? GTE_VFLIP_BIT : 0);