✨ Notify the user if the graph fails to load and why.

Also fixes #7

core/src/komposten/tcs/TetraColourSpace.java

@@ -26,6 +26,9 @@
 import java.util.LinkedList;
 import java.util.List;
 
+import javax.swing.JOptionPane;
+import javax.xml.parsers.ParserConfigurationException;
+
 import com.badlogic.gdx.ApplicationAdapter;
 import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.files.FileHandle;
@@ -46,6 +49,7 @@
 import com.badlogic.gdx.utils.ScreenUtils;
 
 import komposten.tcs.backend.Backend;
+import komposten.tcs.backend.ParseException;
 import komposten.tcs.backend.Style.Colour;
 import komposten.tcs.backend.data.Point;
 import komposten.tcs.input.Action;
@@ -118,9 +122,11 @@ public void create()
 		inputHandler.addListener(inputListener);
 
 		createScreenshotBuffer();
-		loadData();
-		setupPerspectiveCamera();
-		updateViewport();
+		if (loadData())
+		{
+			setupPerspectiveCamera();
+			updateViewport();
+		}
 	}
 
 
@@ -136,14 +142,36 @@ private void createScreenshotBuffer()
 	}
 
 
-	private void loadData()
+	private boolean loadData()
+	{
+		try
+		{
+			backend = new Backend(dataFile, logger);
+			world = new World(backend, camera);
+			userInterface = new UserInterface(backend, world);
+
+			userInterface.attachToInputHandler(inputHandler);
+			world.attachToInputHandler(inputHandler);
+		}
+		catch (IOException | ParserConfigurationException | ParseException e)
+		{
+			showErrorDialog();
+			Gdx.app.exit();
+			return false;
+		}
+
+		return true;
+	}
+
+
+	private void showErrorDialog()
 	{
-		backend = new Backend(dataFile, logger);
-		world = new World(backend, camera);
-		userInterface = new UserInterface(backend, world);
+		String title = "Load error!";
+		String msg = String.format("Errors occurred while loading %s!"
+				+ "%nThe program will terminate."
+				+ "%n%nSee log.txt for more information.", dataFile.getName());
 
-		userInterface.attachToInputHandler(inputHandler);
-		world.attachToInputHandler(inputHandler);
+		JOptionPane.showMessageDialog(null, msg, title, JOptionPane.ERROR_MESSAGE);
 	}
 
 
@@ -255,14 +283,21 @@ private void updateSelectionLog()
 
 	private void updateViewport()
 	{
-		float ratio = Gdx.graphics.getHeight() / (float)Gdx.graphics.getWidth();
-		camera.viewportHeight = ratio;
-		cameraDirty = true;
+		if (camera != null)
+		{
+			float ratio = Gdx.graphics.getHeight() / (float)Gdx.graphics.getWidth();
+			camera.viewportHeight = ratio;
+			cameraDirty = true;
+		}
 
-		spriteCamera.setToOrtho(false, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
-		spriteBatch.setProjectionMatrix(spriteCamera.combined);
+		if (spriteCamera != null)
+		{
+			spriteCamera.setToOrtho(false, Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
+			spriteBatch.setProjectionMatrix(spriteCamera.combined);
+		}
 
-		userInterface.resize(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
+		if (userInterface != null)
+			userInterface.resize(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
 	}
 
 
@@ -278,7 +313,9 @@ public void dispose()
 	{
 		screenshotBuffer.dispose();
 		batch.dispose();
-		userInterface.dispose();
+
+		if (userInterface != null)
+			userInterface.dispose();
 		disposeObjects();
 
 		if (!selectionLog.isEmpty())
@@ -300,7 +337,8 @@ private void disposeObjects()
 			disposable.dispose();
 		}
 
-		world.dispose();
+		if (world != null)
+			world.dispose();
 	}
 
 

core/src/komposten/tcs/backend/Backend.java

@@ -20,6 +20,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.util.List;
 
 import javax.xml.XMLConstants;
 import javax.xml.parsers.DocumentBuilder;
@@ -43,7 +44,7 @@ public class Backend
 	private GraphData graph;
 
 
-	public Backend(File dataFile, Logger logger)
+	public Backend(File dataFile, Logger logger) throws IOException, ParserConfigurationException, ParseException
 	{
 		this.dataFile = dataFile;
 		this.logger = logger;
@@ -64,7 +65,7 @@ public GraphData getGraph()
 	}
 
 
-	private void loadDataFromFile()
+	private void loadDataFromFile() throws IOException, ParserConfigurationException, ParseException
 	{
 		try
 		{
@@ -79,19 +80,32 @@ private void loadDataFromFile()
 		}
 		catch (IOException e)
 		{
-			String msg = "Error reading data file: " + dataFile.getPath();
-			logger.log(Level.FATAL, getClass().getSimpleName(), msg, e, false);
+			logError("Error reading data file: %s", e, dataFile.getPath());
+			throw e;
 		}
 		catch (ParserConfigurationException e)
 		{
-			String msg = "Error creating the XML parser!";
-			logger.log(Level.FATAL, getClass().getSimpleName(), msg, e, false);
+			logError("Error creating the XML parser!", e);
+			throw e;
 		}
 		catch (SAXException e)
 		{
-			String msg = "Error parsing data file: " + dataFile.getPath();
-			logger.log(Level.FATAL, getClass().getSimpleName(), msg, e, false);
+			logError("Error parsing data file %s", e, dataFile.getPath());
+			throw new ParseException(e);
 		}
+		catch (ParseException e)
+		{
+			String msg = "Error parsing data file " + dataFile.getPath() + ": " + e.getMessage();
+			logger.log(Level.FATAL, msg);
+			throw e;
+		}
+	}
+
+
+	private void logError(String formatString, Throwable cause, Object... params)
+	{
+		String msg = String.format(formatString, params);
+		logger.log(Level.FATAL, getClass().getSimpleName(), msg, cause, false);
 	}
 
 
@@ -105,9 +119,20 @@ private void loadConfig(Element root)
 	}
 
 
-	private void loadGraph(Element root)
+	private void loadGraph(Element root) throws ParseException
 	{
-		GraphLoader loader = new GraphLoader(style, logger);
-		graph = loader.load(root);
+		GraphLoader loader = new GraphLoader(style);
+		if (!loader.load(root))
+		{
+			List<String> errors = loader.getErrors();
+
+			StringBuilder message = new StringBuilder();
+			for (String error : errors)
+				message.append("\n").append(error);
+
+			throw new ParseException(message.toString());
+		}
+
+		graph = loader.getResult();
 	}
 }