diff --git a/www-client/src/main/java/fr/agrometinfo/www/client/ui/map/CanvasAttributions.java b/www-client/src/main/java/fr/agrometinfo/www/client/ui/map/CanvasAttributions.java
new file mode 100644
index 0000000000000000000000000000000000000000..ed0c22161cfa82ab66802597e756abe0749e6c41
--- /dev/null
+++ b/www-client/src/main/java/fr/agrometinfo/www/client/ui/map/CanvasAttributions.java
@@ -0,0 +1,126 @@
+package fr.agrometinfo.www.client.ui.map;
+
+import java.util.StringJoiner;
+
+import com.google.gwt.canvas.dom.client.Context2d;
+import com.google.gwt.canvas.dom.client.Context2d.TextAlign;
+import com.google.gwt.canvas.dom.client.TextMetrics;
+import com.google.gwt.core.client.GWT;
+import com.google.gwt.dom.client.CanvasElement;
+import com.google.gwt.dom.client.DivElement;
+import com.google.gwt.dom.client.Document;
+
+import elemental2.dom.DomGlobal;
+import ol.Collection;
+import ol.Map;
+import ol.layer.Base;
+import ol.layer.Group;
+
+/**
+ * Draw the attributions box into HTML canvas of OpenLayers to allow map export.
+ *
+ * At bottom right.
+ *
+ * @author Olivier Maury
+ */
+public final class CanvasAttributions extends CanvasWidget {
+
+ /**
+ * Line height for the lines of title.
+ */
+ private static final int LINE_HEIGHT = 8;
+
+ /**
+ * Margin around the box.
+ */
+ private static final int MARGIN = 2;
+
+ /**
+ * Padding around the text.
+ */
+ private static final int PADDING = 5;
+
+ private static String getAttributions(final Base layer) {
+ GWT.log("CanvasAttributions.getAttributions()");
+ final Object value = layer.get(TileSuppliers.ATTRIBUTIONS);
+ if (value == null) {
+ return null;
+ }
+ String attributions;
+ if (value instanceof String[]) {
+ attributions = String.join("", (String[]) value);
+ } else if (value instanceof String) {
+ attributions = (String) value;
+ } else {
+ return null;
+ }
+ attributions = attributions.trim();
+ if (attributions.startsWith("-")) {
+ attributions = attributions.substring(1).trim();
+ }
+ if (attributions.isEmpty()) {
+ return null;
+ }
+ return attributions;
+ }
+
+ /**
+ * Constructor.
+ *
+ * @param map OpenLayers map.
+ */
+ public CanvasAttributions(final Map map) {
+ super(map);
+ }
+
+ /**
+ * Draw the attribution box with background.
+ */
+ @Override
+ protected void draw() {
+ GWT.log("CanvasAttributions.draw()");
+ final CanvasElement canvas = getCanvas();
+ if (canvas == null) {
+ DomGlobal.console.error("Canvas must not be null!");
+ return;
+ }
+ final StringJoiner sj = new StringJoiner(" - ");
+ final Collection<Base> layers = getMap().getLayerGroup().getLayers();
+ for (final Base l : layers.getArray()) {
+ String attributions = getAttributions(l);
+ if (attributions != null) {
+ sj.add(attributions);
+ } else if (l instanceof Group) {
+ final Group group = (Group) l;
+ for (final Base layer : group.getLayers().getArray()) {
+ if (layer.getVisible()) {
+ attributions = getAttributions(layer);
+ if (attributions != null) {
+ sj.add(attributions);
+ }
+ }
+ }
+ } else {
+ GWT.log("CanvasAttributions.draw() " + l.getClass().getCanonicalName());
+ }
+ }
+ final DivElement div = Document.get().createDivElement();
+ div.setInnerHTML(sj.toString());
+ final String line = div.getInnerText().trim();
+ final Context2d ctx = canvas.getContext2d();
+ ctx.setFont("8px \"Helvetica Neue\", Helvetica, Arial, sans-serif");
+ final TextMetrics measure = ctx.measureText(line);
+ final double width = measure.getWidth();
+ ctx.setFillStyle("rgba(255, 255, 255, .8)");
+ ctx.fillRect(//
+ canvas.getWidth() - width - MARGIN - 2 * PADDING, //
+ canvas.getHeight() - LINE_HEIGHT - MARGIN - 2 * PADDING, //
+ width + 2 * PADDING, //
+ LINE_HEIGHT + 2 * PADDING);
+ ctx.setFillStyle("#000000");
+ ctx.setTextAlign(TextAlign.LEFT);
+ ctx.fillText(line, //
+ canvas.getWidth() - width - MARGIN - PADDING, //
+ canvas.getHeight() - MARGIN - PADDING);
+ }
+}
diff --git a/www-client/src/main/java/fr/agrometinfo/www/client/ui/map/CanvasWidget.java b/www-client/src/main/java/fr/agrometinfo/www/client/ui/map/CanvasWidget.java
new file mode 100644
index 0000000000000000000000000000000000000000..f8715a5c38b4bb6becfe4e5184c07463edc2c09e
--- /dev/null
+++ b/www-client/src/main/java/fr/agrometinfo/www/client/ui/map/CanvasWidget.java
@@ -0,0 +1,78 @@
+package fr.agrometinfo.www.client.ui.map;
+
+import com.google.gwt.dom.client.CanvasElement;
+import com.google.gwt.dom.client.Element;
+import com.google.gwt.dom.client.NodeList;
+
+import ol.Map;
+
+/**
+ * Ancestor for all widgets drawn on the OpenLayers canvas.
+ *
+ * @author Olivier Maury
+ */
+abstract class CanvasWidget {
+ /**
+ * OpenLayers map.
+ */
+ private final Map openLayersMap;
+
+ /**
+ * HTML canvas element.
+ */
+ private CanvasElement canvas;
+
+ /**
+ * Constructor.
+ *
+ * @param map OpenLayers map.
+ */
+ protected CanvasWidget(final Map map) {
+ openLayersMap = map;
+ openLayersMap.on("postcompose", e -> this.draw());
+ }
+
+ /**
+ * Draw the widget when map changes.
+ */
+ protected abstract void draw();
+
+ /**
+ * Find a canvas element in the tree.
+ *
+ * @param root root element
+ * @return found or null
+ */
+ private CanvasElement findCanvas(final Element root) {
+ final NodeList<Element> elems = root.getElementsByTagName("canvas");
+ for (int i = 0; i < elems.getLength(); i++) {
+ final Element elem = elems.getItem(i);
+ if ("canvas".equalsIgnoreCase(elem.getTagName())) {
+ return (CanvasElement) elem;
+ }
+ final CanvasElement found = findCanvas(elem);
+ if (found != null) {
+ return found;
+ }
+ }
+ return null;
+ }
+
+ /**
+ * @return HTML canvas element.
+ */
+ protected CanvasElement getCanvas() {
+ if (canvas == null) {
+ canvas = findCanvas(openLayersMap.getViewport());
+ }
+ return canvas;
+ }
+
+ /**
+ * @return OpenLayers map.
+ */
+ protected Map getMap() {
+ return openLayersMap;
+ }
+
+}