Fixed an issue with identifying similar image collection tilesets

Image collection tilesets were trivially seen as "similar"
in most cases, as long as they were using tiles of the same size. Now,
they need to have the same number of the images and all of the images
need to refer to the same image file.

Closes mapeditor#1113

NEWS

@@ -3,6 +3,7 @@
 * Fixed layer offsets missing in the Lua export
 * Fixed JSON tileset format missing in 'Add External Tileset' action
 * Fixed language selection entries for Portuguese
+* Fixed an issue with copy/pasting when using image collection tilesets
 * Updated Brazilian Portuguese translation
 
 0.14.1 (28 September 2015)

src/libtiled/tileset.cpp

@@ -113,18 +113,46 @@ bool Tileset::loadFromImage(const QImage &image,
     return true;
 }
 
+static bool sameTileImages(const Tileset &a, const Tileset &b)
+{
+    Q_ASSERT(a.tileCount() == b.tileCount());
+
+    for (int i = 0; i < a.tileCount(); ++i) {
+        const Tile *tileA = a.tileAt(i);
+        const Tile *tileB = b.tileAt(i);
+        if (tileA->imageSource() != tileB->imageSource())
+            return false;
+    }
+
+    return true;
+}
+
 SharedTileset Tileset::findSimilarTileset(const QVector<SharedTileset> &tilesets) const
 {
     foreach (const SharedTileset &candidate, tilesets) {
-        if (candidate != this
-            && candidate->imageSource() == imageSource()
-            && candidate->tileWidth() == tileWidth()
-            && candidate->tileHeight() == tileHeight()
-            && candidate->tileSpacing() == tileSpacing()
-            && candidate->margin() == margin()) {
-                return candidate;
-        }
+        Q_ASSERT(candidate != this);
+
+        if (candidate->tileCount() != tileCount())
+            continue;
+        if (candidate->imageSource() != imageSource())
+            continue;
+        if (candidate->tileSize() != tileSize())
+            continue;
+        if (candidate->tileSpacing() != tileSpacing())
+            continue;
+        if (candidate->margin() != margin())
+            continue;
+        if (candidate->tileOffset() != tileOffset())
+            continue;
+
+        // For an image collection tileset, check the image sources
+        if (imageSource().isEmpty())
+            if (!sameTileImages(*this, *candidate))
+                continue;
+
+        return candidate;
     }
+
     return SharedTileset();
 }