Now you can open the documentation from the help menu.

src/main/java/de/neemann/digital/gui/DocumentationLocator.java

@@ -0,0 +1,96 @@
+package de.neemann.digital.gui;
+
+import de.neemann.digital.draw.library.ElementLibrary;
+import de.neemann.digital.lang.Lang;
+import de.neemann.gui.ErrorMessage;
+import de.neemann.gui.ToolTipAction;
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.io.File;
+import java.io.IOException;
+import java.net.URISyntaxException;
+
+/**
+ * Used to open documentation
+ */
+public class DocumentationLocator {
+
+    private final File folder;
+
+    /**
+     * Creates a new instance
+     */
+    public DocumentationLocator() {
+        File folder = null;
+        try {
+            String path = ElementLibrary.class.getProtectionDomain().getCodeSource().getLocation().toURI().getPath().replace('\\', '/');
+            if (path.endsWith("/target/classes/"))
+                folder = new File(path.substring(0, path.length() - 9) + "/xslt");
+            else if (path.endsWith("/target/Digital.jar"))
+                folder = new File(path.substring(0, path.length() - 11) + "/xslt");
+            else if (path.endsWith("Digital.jar"))
+                folder = new File(path.substring(0, path.length() - 12) + "/docu");
+        } catch (URISyntaxException e) {
+            // do nothing on error
+        }
+        if (folder != null && folder.exists())
+            this.folder = folder;
+        else
+            this.folder = null;
+    }
+
+    /**
+     * Adds the documentation to the given menu
+     *
+     * @param help the menu to add the documentation to
+     */
+    public void addMenuTo(JMenu help) {
+        if (folder != null) {
+            File[] files = folder.listFiles((file, name) -> name.endsWith(".pdf"));
+            if (files != null && files.length > 0) {
+
+                String language = "_" + Lang.currentLanguage().getName() + ".pdf";
+                File found = null;
+                for (File f : files)
+                    if (f.getName().endsWith(language))
+                        found = f;
+
+                if (found == null) {
+                    JMenu docu = new JMenu(Lang.get("menu_pdfDocumentation"));
+                    help.add(docu);
+                    for (File f : files)
+                        docu.add(new OpenPDFAction(f).createJMenuItem());
+                } else
+                    help.add(new OpenPDFAction(found, Lang.get("menu_pdfDocumentation")));
+            }
+        }
+    }
+
+    private static final class OpenPDFAction extends ToolTipAction {
+        private final File f;
+
+        private OpenPDFAction(File f) {
+            this(f, Lang.get("menu_openPdfDocumentation", f.getName()));
+        }
+
+        private OpenPDFAction(File f, String name) {
+            super(name);
+            this.f = f;
+        }
+
+        @Override
+        public void actionPerformed(ActionEvent actionEvent) {
+            try {
+                Desktop desktop = Desktop.isDesktopSupported() ? Desktop.getDesktop() : null;
+                if (desktop != null && desktop.isSupported(Desktop.Action.OPEN))
+                    desktop.open(f);
+                else
+                    throw new IOException("could not open pdf document");
+            } catch (IOException e) {
+                new ErrorMessage(Lang.get("msg_errorOpeningDocumentation")).addCause(e).show();
+            }
+        }
+    }
+}

src/main/java/de/neemann/digital/gui/Main.java

@@ -249,6 +249,7 @@ public final class Main extends JFrame implements ClosingWindowListener.ConfirmS
                 }
             }
         }.setToolTip(Lang.get("menu_help_elements_tt")).createJMenuItem());
+        new DocumentationLocator().addMenuTo(help);
 
         new ToolTipAction("insertLast") {
             @Override

src/main/resources/lang/lang_de.xml

@@ -918,6 +918,9 @@ Sind evtl. die Namen der Variablen nicht eindeutig?</string>
     <string name="menu_addPowerSupply_tt">Erweitert die Schaltung um eine Spannungsversorung.</string>
     <string name="menu_exportVHDL">Export zu VHDL</string>
     <string name="menu_exportVHDL_tt">Exportiert die Schaltung zu VHDL</string>
+    <string name="menu_pdfDocumentation">Dokumentation</string>
+    <string name="menu_openPdfDocumentation">Öffne {0}</string>
+    <string name="msg_errorOpeningDocumentation">Fehler beim Öffnen einer PDF-Datei!</string>
 
     <string name="message">Digital
 

src/main/resources/lang/lang_en.xml

@@ -904,6 +904,9 @@ The names of the variables may not be unique.</string>
     <string name="menu_addPowerSupply_tt">Adds a power supply to the circuit.</string>
     <string name="menu_exportVHDL">Export to VHDL</string>
     <string name="menu_exportVHDL_tt">Exports the circuit to VHDL</string>
+    <string name="menu_pdfDocumentation">Documentation</string>
+    <string name="menu_openPdfDocumentation">Open {0}</string>
+    <string name="msg_errorOpeningDocumentation">Error opening a PDF file!</string>
 
     <string name="message">Digital
 

src/test/java/de/neemann/digital/docu/DocuTest.java

@@ -209,7 +209,7 @@ public class DocuTest extends TestCase {
         for (Language l : Lang.getBundle().getSupportedLanguages()) {
             // set language
             Lang.setActualRuntimeLanguage(l);
-            final String basename = "docu_" + l.getName();
+            final String basename = "Documentation_" + l.getName();
             // write xml
             File xml = new File(target, basename + ".xml");
             try (Writer w = new OutputStreamWriter(new FileOutputStream(xml), "UTF-8")) {