bridge: be tolerant to missing references

MIGRATING_FROM_BATIK.md

@@ -1,5 +1,24 @@
 # Migrating from Apache Batik
 
+ There are several reasons why EchoSVG is not a drop-in replacement for Apache
+Batik:
+
+- Avoid using Apache Software Foundation package names and trademarks.
+
+- Improved conformance to the SVG and CSS specifications.
+
+- Better user experience (_e.g._ the `codec`-`transcoder` merge).
+
+- A circularity with Apache FOP. To render PDF images, Batik uses FOP which in
+  turn uses Batik, so depending on FOP would imply mixing EchoSVG and Batik. See
+  issue [#10](https://github.com/css4j/echosvg/issues/10).
+
+- Changes in the Java™ Platform.
+
+<br/>
+
+## Migration checklist
+
  To migrate from Apache Batik, you generally have to deal with the following:
 
 1) Package names are now prefixed by `io.sf.carte.echosvg` instead of
@@ -40,3 +59,6 @@
    `ApplicationSecurityEnforcer.createSecurityEnforcer(Class, String)` instead.
 
 9) `BridgeContext` (in the `bridge` module) gained a `close` method.
+
+10) `SVGAnimationElementBridge.initializeAnimation()` gained a `BridgeContext`
+   argument and now returns a `boolean`.

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/AbstractSVGGradientElementBridge.java

@@ -178,8 +178,11 @@ protected static List<Stop> extractStop(Element paintElement, float opacity, Bri
 				throw new BridgeException(ctx, paintElement, ERR_XLINK_HREF_CIRCULAR_DEPENDENCIES,
 						new Object[] { uri });
 			}
-			refs.add(purl);
 			paintElement = ctx.getReferencedElement(paintElement, uri);
+			if (paintElement == null) {
+				return null; // Missing reference
+			}
+			refs.add(purl);
 		}
 	}
 

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/BridgeContext.java

@@ -749,7 +749,12 @@ public Node getReferencedNode(Element e, String uri) {
 			URIResolver ur = createURIResolver(document, documentLoader);
 			Node ref = ur.getNode(uri, e);
 			if (ref == null) {
-				throw new BridgeException(this, e, ERR_URI_BAD_TARGET, new Object[] { uri });
+				BridgeException ex = new BridgeException(this, e, ERR_URI_BAD_TARGET, new Object[] { uri });
+				if (userAgent != null) {
+					userAgent.displayError(ex);
+				} else {
+					throw ex;
+				}
 			} else {
 				SVGOMDocument refDoc = (SVGOMDocument) (ref.getNodeType() == Node.DOCUMENT_NODE ? ref
 						: ref.getOwnerDocument());
@@ -763,8 +768,8 @@ public Node getReferencedNode(Element e, String uri) {
 				if (refDoc != document) {
 					createSubBridgeContext(refDoc);
 				}
-				return ref;
 			}
+			return ref;
 		} catch (MalformedURLException ex) {
 			throw new BridgeException(this, e, ex, ERR_URI_MALFORMED, new Object[] { uri });
 		} catch (InterruptedIOException ex) {

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/CSSUtilities.java

@@ -627,9 +627,23 @@ public static Filter convertFilter(Element filteredElement, GraphicsNode filtere
 		case CSSPrimitiveValue.CSS_URI:
 			String uri = v.getStringValue();
 			Element filter = ctx.getReferencedElement(filteredElement, uri);
+			if (filter == null) {
+				return null; // Missing reference
+			}
 			Bridge bridge = ctx.getBridge(filter);
-			if (bridge == null || !(bridge instanceof FilterBridge)) {
-				throw new BridgeException(ctx, filteredElement, ERR_CSS_URI_BAD_TARGET, new Object[] { uri });
+			if (bridge == null) {
+				// Assume that the cause of this was already reported
+				return null;
+			}
+			if (!(bridge instanceof FilterBridge)) {
+				BridgeException ex = new BridgeException(ctx, filteredElement,
+						ERR_CSS_URI_BAD_TARGET, new Object[] { uri });
+				UserAgent userAgent = ctx.getUserAgent();
+				if (userAgent == null) {
+					throw ex;
+				}
+				userAgent.displayError(ex);
+				return null;
 			}
 			return ((FilterBridge) bridge).createFilter(ctx, filter, filteredElement, filteredNode);
 		default:
@@ -660,9 +674,23 @@ public static ClipRable convertClipPath(Element clippedElement, GraphicsNode cli
 		case CSSPrimitiveValue.CSS_URI:
 			String uri = v.getStringValue();
 			Element cp = ctx.getReferencedElement(clippedElement, uri);
+			if (cp == null) {
+				return null; // Missing reference
+			}
 			Bridge bridge = ctx.getBridge(cp);
-			if (bridge == null || !(bridge instanceof ClipBridge)) {
-				throw new BridgeException(ctx, clippedElement, ERR_CSS_URI_BAD_TARGET, new Object[] { uri });
+			if (bridge == null) {
+				// Assume that the cause of this was already reported
+				return null;
+			}
+			if (!(bridge instanceof ClipBridge)) {
+				BridgeException ex = new BridgeException(ctx, clippedElement,
+						ERR_CSS_URI_BAD_TARGET, new Object[] { uri });
+				UserAgent userAgent = ctx.getUserAgent();
+				if (userAgent == null) {
+					throw ex;
+				}
+				userAgent.displayError(ex);
+				return null;
 			}
 			return ((ClipBridge) bridge).createClip(ctx, cp, clippedElement, clippedNode);
 		default:
@@ -703,9 +731,23 @@ public static Mask convertMask(Element maskedElement, GraphicsNode maskedNode, B
 		case CSSPrimitiveValue.CSS_URI:
 			String uri = v.getStringValue();
 			Element m = ctx.getReferencedElement(maskedElement, uri);
+			if (m == null) {
+				return null; // Missing reference
+			}
 			Bridge bridge = ctx.getBridge(m);
-			if (bridge == null || !(bridge instanceof MaskBridge)) {
-				throw new BridgeException(ctx, maskedElement, ERR_CSS_URI_BAD_TARGET, new Object[] { uri });
+			if (bridge == null) {
+				// Assume that the cause of this was already reported
+				return null;
+			}
+			if (!(bridge instanceof MaskBridge)) {
+				BridgeException ex = new BridgeException(ctx, maskedElement, ERR_CSS_URI_BAD_TARGET,
+						new Object[] { uri });
+				UserAgent userAgent = ctx.getUserAgent();
+				if (userAgent == null) {
+					throw ex;
+				}
+				userAgent.displayError(ex);
+				return null;
 			}
 			return ((MaskBridge) bridge).createMask(ctx, m, maskedElement, maskedNode);
 		default:

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/CursorManager.java

@@ -430,6 +430,10 @@ protected Filter cursorHrefToFilter(Element cursorElement, ParsedURL purl, Point
 			}
 			GraphicsNode node = ctx.getGVTBuilder().build(ctx, rootElement);
 
+			if (node == null) {
+				return null;
+			}
+
 			//
 			// The cursorSize define the viewport into which the
 			// cursor is displayed. That viewport is platform

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/FontFace.java

@@ -144,7 +144,8 @@ protected GVTFontFamily getFontFamily(BridgeContext ctx, ParsedURL purl) {
 		if (purl.getRef() != null) {
 			// Reference must be to a SVGFont.
 			Element ref = ctx.getReferencedElement(e, purlStr);
-			if (!ref.getNamespaceURI().equals(SVG_NAMESPACE_URI) || !ref.getLocalName().equals(SVG_FONT_TAG)) {
+			if (ref == null || !ref.getNamespaceURI().equals(SVG_NAMESPACE_URI)
+					|| !ref.getLocalName().equals(SVG_FONT_TAG)) {
 				return null;
 			}
 

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/MultiResGraphicsNode.java

@@ -221,9 +221,10 @@ public GraphicsNode getGraphicsNode(int idx) {
 
 		try {
 			GVTBuilder builder = ctx.getGVTBuilder();
-			GraphicsNode gn;
-			gn = builder.build(ctx, srcElems[idx]);
-			srcs[idx] = new SoftReference<>(gn);
+			GraphicsNode gn = builder.build(ctx, srcElems[idx]);
+			if (gn != null) {
+				srcs[idx] = new SoftReference<>(gn);
+			}
 			return gn;
 		} catch (Exception ex) {
 			ex.printStackTrace();

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/PaintServer.java

@@ -124,9 +124,22 @@ public static Marker convertMarker(Element e, Value v, BridgeContext ctx) {
 		} else {
 			String uri = v.getStringValue();
 			Element markerElement = ctx.getReferencedElement(e, uri);
+			if (markerElement == null) {
+				return null; // Missing reference
+			}
 			Bridge bridge = ctx.getBridge(markerElement);
-			if (bridge == null || !(bridge instanceof MarkerBridge)) {
-				throw new BridgeException(ctx, e, ERR_CSS_URI_BAD_TARGET, new Object[] { uri });
+			if (bridge == null) {
+				// Assume that the cause of this was already reported
+				return null;
+			}
+			if (!(bridge instanceof MarkerBridge)) {
+				BridgeException ex = new BridgeException(ctx, e, ERR_CSS_URI_BAD_TARGET, new Object[] { uri });
+				UserAgent userAgent = ctx.getUserAgent();
+				if (userAgent == null) {
+					throw ex;
+				}
+				userAgent.displayError(ex);
+				return null;
 			}
 			return ((MarkerBridge) bridge).createMarker(ctx, markerElement, e);
 		}
@@ -315,10 +328,24 @@ public static Paint convertURIPaint(Element paintedElement, GraphicsNode painted
 
 		String uri = paintDef.getStringValue();
 		Element paintElement = ctx.getReferencedElement(paintedElement, uri);
+		if (paintElement == null) {
+			return null; // Missing reference
+		}
 
 		Bridge bridge = ctx.getBridge(paintElement);
-		if (bridge == null || !(bridge instanceof PaintBridge)) {
-			throw new BridgeException(ctx, paintedElement, ERR_CSS_URI_BAD_TARGET, new Object[] { uri });
+		if (bridge == null) {
+			// Assume that the cause of this was already reported
+			return null;
+		}
+		if (!(bridge instanceof PaintBridge)) {
+			BridgeException ex = new BridgeException(ctx, paintedElement, ERR_CSS_URI_BAD_TARGET,
+					new Object[] { uri });
+			UserAgent userAgent = ctx.getUserAgent();
+			if (userAgent == null) {
+				throw ex;
+			}
+			userAgent.displayError(ex);
+			return null;
 		}
 		return ((PaintBridge) bridge).createPaint(ctx, paintElement, paintedElement, paintedNode, opacity);
 	}

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/SVGAnimateMotionElementBridge.java

@@ -153,8 +153,10 @@ protected ExtendedGeneralPath parsePath() {
 					&& SVG_MPATH_TAG.equals(n.getLocalName())) {
 				String uri = XLinkSupport.getXLinkHref((Element) n);
 				Element path = ctx.getReferencedElement(element, uri);
-				if (!SVG_NAMESPACE_URI.equals(path.getNamespaceURI()) || !SVG_PATH_TAG.equals(path.getLocalName())) {
-					throw new BridgeException(ctx, element, ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+				if (path == null || !SVG_NAMESPACE_URI.equals(path.getNamespaceURI())
+						|| !SVG_PATH_TAG.equals(path.getLocalName())) {
+					throw new BridgeException(ctx, element, ErrorConstants.ERR_URI_BAD_TARGET,
+							new Object[] { uri });
 				}
 				SVGOMPathElement pathElt = (SVGOMPathElement) path;
 				AWTPathProducer app = new AWTPathProducer();
@@ -295,18 +297,27 @@ public AnimatableValue getUnderlyingValue() {
 	/**
 	 * Parses the animation element's target attributes and adds it to the
 	 * document's AnimationEngine.
+	 * @param ctx the bridge context to use in error reporting.
+	 * @return true if the initialization was successful.
 	 */
 	@Override
-	protected void initializeAnimation() {
+	protected boolean initializeAnimation(BridgeContext ctx) {
 		// Determine the target element.
 		String uri = XLinkSupport.getXLinkHref(element);
 		Node t;
 		if (uri.length() == 0) {
 			t = element.getParentNode();
 		} else {
 			t = ctx.getReferencedElement(element, uri);
-			if (t.getOwnerDocument() != element.getOwnerDocument()) {
-				throw new BridgeException(ctx, element, ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+			if (t == null || t.getOwnerDocument() != element.getOwnerDocument()) {
+				BridgeException ex = new BridgeException(ctx, element,
+						ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+				UserAgent userAgent = ctx.getUserAgent();
+				if (userAgent == null) {
+					throw ex;
+				}
+				userAgent.displayError(ex);
+				return false;
 			}
 		}
 		animationTarget = null;
@@ -315,13 +326,21 @@ protected void initializeAnimation() {
 			animationTarget = targetElement;
 		}
 		if (animationTarget == null) {
-			throw new BridgeException(ctx, element, ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+			BridgeException ex = new BridgeException(ctx, element,
+					ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+			UserAgent userAgent = ctx.getUserAgent();
+			if (userAgent == null) {
+				throw ex;
+			}
+			userAgent.displayError(ex);
+			return false;
 		}
 
 		// Add the animation.
 		timedElement = createTimedElement();
 		animation = createAnimation(animationTarget);
 		eng.addAnimation(animationTarget, AnimationEngine.ANIM_TYPE_OTHER, attributeNamespaceURI, attributeLocalName,
 				animation);
+		return true;
 	}
 }

echosvg-bridge/src/main/java/io/sf/carte/echosvg/bridge/SVGAnimationElementBridge.java

@@ -144,8 +144,9 @@ public void handleElement(BridgeContext ctx, Element e) {
 			b.eng = ctx.getAnimationEngine();
 			b.element.setSVGContext(b);
 			if (b.eng.hasStarted()) {
-				b.initializeAnimation();
-				b.initializeTimedElement();
+				if (b.initializeAnimation(ctx)) {
+					b.initializeTimedElement();
+				}
 			} else {
 				b.eng.addInitialBridge(b);
 			}
@@ -155,17 +156,26 @@ public void handleElement(BridgeContext ctx, Element e) {
 	/**
 	 * Parses the animation element's target attributes and adds it to the
 	 * document's AnimationEngine.
+	 * @param ctx the bridge context to use in error reporting.
+	 * @return true if the initialization was successful.
 	 */
-	protected void initializeAnimation() {
+	protected boolean initializeAnimation(BridgeContext ctx) {
 		// Determine the target element.
 		String uri = XLinkSupport.getXLinkHref(element);
 		Node t;
 		if (uri.length() == 0) {
 			t = element.getParentNode();
 		} else {
 			t = ctx.getReferencedElement(element, uri);
-			if (t.getOwnerDocument() != element.getOwnerDocument()) {
-				throw new BridgeException(ctx, element, ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+			if (t == null || t.getOwnerDocument() != element.getOwnerDocument()) {
+				BridgeException ex = new BridgeException(ctx, element,
+						ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+				UserAgent userAgent = ctx.getUserAgent();
+				if (userAgent == null) {
+					throw ex;
+				}
+				userAgent.displayError(ex);
+				return false;
 			}
 		}
 		animationTarget = null;
@@ -174,7 +184,14 @@ protected void initializeAnimation() {
 			animationTarget = targetElement;
 		}
 		if (animationTarget == null) {
-			throw new BridgeException(ctx, element, ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+			BridgeException ex = new BridgeException(ctx, element,
+					ErrorConstants.ERR_URI_BAD_TARGET, new Object[] { uri });
+			UserAgent userAgent = ctx.getUserAgent();
+			if (userAgent == null) {
+				throw ex;
+			}
+			userAgent.displayError(ex);
+			return false;
 		}
 
 		// Get the attribute/property name.
@@ -197,8 +214,14 @@ protected void initializeAnimation() {
 		if (animationType == AnimationEngine.ANIM_TYPE_CSS && !targetElement.isPropertyAnimatable(attributeLocalName)
 				|| animationType == AnimationEngine.ANIM_TYPE_XML
 						&& !targetElement.isAttributeAnimatable(attributeNamespaceURI, attributeLocalName)) {
-			throw new BridgeException(ctx, element, "attribute.not.animatable",
+			BridgeException ex = new BridgeException(ctx, element, "attribute.not.animatable",
 					new Object[] { targetElement.getNodeName(), an });
+			UserAgent userAgent = ctx.getUserAgent();
+			if (userAgent == null) {
+				throw ex;
+			}
+			userAgent.displayError(ex);
+			return false;
 		}
 
 		// Check that the attribute/property is animatable with this
@@ -210,14 +233,21 @@ protected void initializeAnimation() {
 			type = targetElement.getAttributeType(attributeNamespaceURI, attributeLocalName);
 		}
 		if (!canAnimateType(type)) {
-			throw new BridgeException(ctx, element, "type.not.animatable",
+			BridgeException ex = new BridgeException(ctx, element, "type.not.animatable",
 					new Object[] { targetElement.getNodeName(), an, element.getNodeName() });
+			UserAgent userAgent = ctx.getUserAgent();
+			if (userAgent == null) {
+				throw ex;
+			}
+			userAgent.displayError(ex);
+			return false;
 		}
 
 		// Add the animation.
 		timedElement = createTimedElement();
 		animation = createAnimation(animationTarget);
 		eng.addAnimation(animationTarget, animationType, attributeNamespaceURI, attributeLocalName, animation);
+		return true;
 	}
 
 	/**