add function to get visible tiles only

src/org/oscim/renderer/GLRenderer.java

@@ -320,6 +320,8 @@ public class GLRenderer implements GLSurfaceView.Renderer {
 		}
 	}
 
+	private static Object tilelock = new Object();
+
 	static void draw() {
 		long start = 0;
 
@@ -372,6 +374,8 @@ public class GLRenderer implements GLSurfaceView.Renderer {
 		MapTile[] tiles = mDrawTiles.tiles;
 
 		if (changed) {
+			synchronized (GLRenderer.tilelock) {
+
 				// get visible tiles
 				for (int i = 0; i < tileCnt; i++)
 					tiles[i].isVisible = false;
@@ -380,7 +384,8 @@ public class GLRenderer implements GLSurfaceView.Renderer {
 				// zoom-level changed.
 				byte z = tiles[0].zoomLevel;
 				float div = FastMath.pow(z - pos.zoomLevel);
-
+				if (div != 1)
+					Log.d(TAG, "tiles not from current zoom level");
 				// transform screen coordinates to tile coordinates
 				float scale = pos.scale / div;
 				float px = (float) pos.x * div;
@@ -394,6 +399,7 @@ public class GLRenderer implements GLSurfaceView.Renderer {
 				mHolderCount = 0;
 				mScanBox.scan(coords, z);
 			}
+		}
 
 		tileCnt += mHolderCount;
 
@@ -506,6 +512,40 @@ public class GLRenderer implements GLSurfaceView.Renderer {
 		return ((t.tileX % 4) + (t.tileY % 4 * 4) + 1);
 	}
 
+	public static TileSet getVisibleTiles(TileSet td) {
+		if (mDrawTiles == null)
+			return td;
+
+		MapTile[] newTiles = mDrawTiles.tiles;
+		int cnt = mDrawTiles.cnt;
+		MapTile[] nextTiles;
+
+		synchronized (TileManager.tilelock) {
+			// lock tiles (and their proxies) to not be removed from cache
+			for (int i = 0; i < cnt; i++)
+				if (newTiles[i].isVisible)
+					newTiles[i].lock();
+
+			if (td == null)
+				td = new TileSet(newTiles.length);
+
+			nextTiles = td.tiles;
+
+			// unlock previously active tiles
+			for (int i = 0, n = td.cnt; i < n; i++)
+				nextTiles[i].unlock();
+		}
+
+		synchronized (GLRenderer.tilelock) {
+			// copy newTiles to nextTiles
+			td.cnt = 0;
+			for (int i = 0; i < cnt; i++)
+				if (newTiles[i].isVisible)
+					nextTiles[td.cnt++] = newTiles[i];
+		}
+		return td;
+	}
+
 	@Override
 	public void onSurfaceChanged(GL10 glUnused, int width, int height) {
 		Log.d(TAG, "SurfaceChanged:" + mNewSurface + " " + width + " " + height);