Introduce a global taskbar on the welcomeHTML page to allow global search.

Global search is a search on all zims.

src/server/kiwix-serve.cpp

@@ -138,11 +138,20 @@ void introduceTaskbar(string& content, const string& humanReadableBookId)
                    ? " #kiwix_serve_taskbar_library_button { display: none }"
                    : "")
             + "</style>");
+    if ( humanReadableBookId.empty() ) {
+      content = appendToFirstOccurence(
+          content,
+          "<body[^>]*>",
+          RESOURCE::global_taskbar_html_part);
+    } else {
       content = appendToFirstOccurence(
           content,
           "<body[^>]*>",
           replaceRegex(
-            RESOURCE::taskbar_html_part, humanReadableBookId, "__CONTENT__"));
+             RESOURCE::taskbar_html_part,
+             humanReadableBookId,
+             "__CONTENT__"));
+    }
   }
 }
 
@@ -982,6 +991,8 @@ int main(int argc, char** argv)
   welcomeHTML
       = replaceRegex(RESOURCE::home_html_tmpl, welcomeBooksHtml, "__BOOKS__");
 
+  introduceTaskbar(welcomeHTML, "");
+
 #ifndef _WIN32
   /* Fork if necessary */
   if (daemonFlag) {