NXT-4596: Add BrowserService interface and OSGi service tracker

org.knime.core.ui/META-INF/MANIFEST.MF

@@ -20,6 +20,7 @@ Export-Package: org.knime.core.ui;x-internal:=true,
  org.knime.core.ui.workflowcoach.data;x-internal:=true,
  org.knime.core.ui.wrapper;x-internal:=true,
  org.knime.core.webui;x-internal:=true,
+ org.knime.core.webui.browser;x-internal:=true,
  org.knime.core.webui.data;x-internal:=true,
  org.knime.core.webui.data.rpc;x-internal:=true,
  org.knime.core.webui.data.rpc.json.impl;x-internal:=true,

org.knime.core.ui/src/eclipse/org/knime/core/ui/CoreUIPlugin.java

@@ -48,10 +48,14 @@
  */
 package org.knime.core.ui;
 
+import java.util.Optional;
+
 import org.knime.core.node.workflow.NodeContext;
 import org.knime.core.ui.node.workflow.ContextObjectSupplierUI;
+import org.knime.core.webui.browser.BrowserService;
 import org.osgi.framework.BundleActivator;
 import org.osgi.framework.BundleContext;
+import org.osgi.util.tracker.ServiceTracker;
 
 /**
  * Activator for the {@code org.knime.core.ui} plugin.
@@ -60,14 +64,33 @@
  */
 public class CoreUIPlugin implements BundleActivator {
 
+    private static CoreUIPlugin instance;
+
+    private ServiceTracker<BrowserService, BrowserService> m_browserServiceTracker;
+
     @Override
     public void start(final BundleContext context) throws Exception {
+        instance = this; // NOSONAR (static assignment)
         NodeContext.addContextObjectSupplier(new ContextObjectSupplierUI());
+        m_browserServiceTracker = new ServiceTracker<>(context, BrowserService.class, null);
+        m_browserServiceTracker.open();
     }
 
     @Override
     public void stop(final BundleContext context) throws Exception {
-        //
+        m_browserServiceTracker.close();
+        m_browserServiceTracker = null;
+        instance = null;
+    }
+
+    /**
+     * Returns the registered {@link BrowserService}, if any.
+     *
+     * @return the browser service, or an empty {@link Optional} if none is registered
+     * @since 5.12
+     */
+    public static Optional<BrowserService> getBrowserService() {
+        return Optional.ofNullable(instance.m_browserServiceTracker).map(ServiceTracker::getService);
     }
 
 }

org.knime.core.ui/src/eclipse/org/knime/core/webui/browser/BrowserService.java

@@ -0,0 +1,115 @@
+/*
+ * ------------------------------------------------------------------------
+ *
+ *  Copyright by KNIME AG, Zurich, Switzerland
+ *  Website: http://www.knime.com; Email: contact@knime.com
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License, Version 3, as
+ *  published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses>.
+ *
+ *  Additional permission under GNU GPL version 3 section 7:
+ *
+ *  KNIME interoperates with ECLIPSE solely via ECLIPSE's plug-in APIs.
+ *  Hence, KNIME and ECLIPSE are both independent programs and are not
+ *  derived from each other. Should, however, the interpretation of the
+ *  GNU GPL Version 3 ("License") under any applicable laws result in
+ *  KNIME and ECLIPSE being a combined program, KNIME AG herewith grants
+ *  you the additional permission to use and propagate KNIME together with
+ *  ECLIPSE with only the license terms in place for ECLIPSE applying to
+ *  ECLIPSE and the GNU GPL Version 3 applying for KNIME, provided the
+ *  license terms of ECLIPSE themselves allow for the respective use and
+ *  propagation of ECLIPSE together with KNIME.
+ *
+ *  Additional permission relating to nodes for KNIME that extend the Node
+ *  Extension (and in particular that are based on subclasses of NodeModel,
+ *  NodeDialog, and NodeView) and that only interoperate with KNIME through
+ *  standard APIs ("Nodes"):
+ *  Nodes are deemed to be separate and independent programs and to not be
+ *  covered works.  Notwithstanding anything to the contrary in the
+ *  License, the License does not apply to Nodes, you are not required to
+ *  license Nodes under the License, and you are granted a license to
+ *  prepare and propagate Nodes, in each case even if such Nodes are
+ *  propagated with or for interoperation with KNIME.  The owner of a Node
+ *  may freely choose the license terms applicable to such Node, including
+ *  when such Node is propagated with or for interoperation with KNIME.
+ *
+ * ------------------------------------------------------------------------
+ */
+package org.knime.core.webui.browser;
+
+import java.io.IOException;
+import java.util.Optional;
+
+import org.knime.core.ui.CoreUIPlugin;
+
+/**
+ * Service for headless browser rendering. All parameters are serializable (String, byte[], int, long, boolean) so this
+ * interface can be exported as an OSGi Remote Service via ECF.
+ *
+ * <p>
+ * Callers are responsible for converting node/component views to JSON page content (e.g. via
+ * {@code AbstractPageManager.createWizardPageForImageGeneration}) before invoking this service.
+ *
+ * @author Martin Horn, KNIME GmbH, Konstanz, Germany
+ *
+ * @since 5.12
+ */
+public interface BrowserService {
+
+    /**
+     * Returns the highest-priority registered {@link BrowserService}, if any. The service is looked up via the OSGi
+     * service registry.
+     *
+     * @return the active browser service, or empty if none is registered
+     */
+    static Optional<BrowserService> get() {
+        return CoreUIPlugin.getBrowserService();
+    }
+
+    /**
+     * Renders content (image or report) from a JSON web-node-page using a headless browser.
+     *
+     * @param pageJson the page content serialized as a JSON string (e.g. from
+     *            {@code JSONWebNodePage.toJsonString()} or a report page)
+     * @param callbackId unique ID for result extraction (e.g. "generatedImage_&lt;uuid&gt;")
+     * @param width the viewport width in pixels
+     * @param height the viewport height in pixels
+     * @param timeoutMs maximum wait time in milliseconds
+     * @param screenshotFallback if {@code true}, captures a screenshot as fallback when the content callback times out
+     *            (useful for image generation); if {@code false}, throws on timeout (appropriate for report generation)
+     * @return the rendered content (image data string or report HTML)
+     * @throws IOException if an error occurs during rendering
+     */
+    String renderContent(String pageJson, String callbackId, int width, int height, long timeoutMs,
+        boolean screenshotFallback) throws IOException;
+
+    /**
+     * Converts HTML content to PDF using a headless browser.
+     *
+     * @param htmlContent the HTML document as UTF-8 bytes
+     * @param timeoutMs maximum wait time in milliseconds
+     * @return the PDF file content as bytes
+     * @throws IOException if an error occurs during rendering
+     */
+    byte[] printToPdf(byte[] htmlContent, long timeoutMs) throws IOException;
+
+    /**
+     * Opens the given URL in a browser window. Used to drive browser-based flows (e.g.&nbsp;OAuth) from a controllable
+     * browser instance. The default implementation is a no-op; implementations that provide an interactive browser
+     * (e.g.&nbsp;the local CEF implementation) should override this method.
+     *
+     * @param url the URL to open
+     */
+    default void openBrowserWindow(final String url) {
+        // no-op by default; overridden by implementations that provide an interactive browser
+    }
+}