AppImage - add support for embedded documentation

src/Gui/Assistant.cpp

@@ -99,6 +99,33 @@ bool Assistant::startAssistant()
         QString doc = QString::fromUtf8(App::Application::getHelpDir().c_str());
         QString qhc = doc + exe.toLower() + QLatin1String(".qhc");
 
+        // AppImage mount location changes on each start. Assistant caches freecad.qhc
+        // file and sets an absolute path. As a result embedded documentation only works
+        // on the first AppImage start. Register the .gch file, to overcome the issue.
+        static bool start = true;
+        if (start) {
+            char* appimage = getenv("APPIMAGE");
+            if (appimage) {
+                QString qch = doc + exe.toLower() + QLatin1String(".qch");
+                QFileInfo fi(qch);
+                if (!fi.isReadable()) {
+                    QMessageBox::critical(0, tr("%1 Help").arg(exe),
+                        tr("%1 help files not found (%2). You might need to install the %1 documentation package.").arg(exe, qch));
+                    return false;
+                }
+                Base::Console().Log("Help file at %s\n", (const char*)qch.toUtf8());
+                QStringList args;
+                args << QLatin1String("-register") << qch;
+                proc->start(app, args);
+                if (!proc->waitForFinished(50000)) {
+                    QMessageBox::critical(0, tr("%1 Help").arg(exe),
+                        tr("Unable to launch Qt Assistant (%1)").arg(app));
+                    return false;
+                }
+            }
+            start = false;
+        }
+
         QFileInfo fi(qhc);
         if (!fi.isReadable()) {
             QMessageBox::critical(0, tr("%1 Help").arg(exe),