CrealityPrint: default Device-tab WebView URL to Mainsail on :4408

K-series printers (K2, K2 Plus, K2 Pro) ship with Mainsail on port
4408. Port 80 hosts only the Creality control/upload API, which
returns 404 for unknown paths and renders as a blank/404 page in
Orca Device tab.

Override CrealityPrint::get_print_host_webui() to default to
http://<host>:4408/ when the user has not explicitly set
print_host_webui, giving K-series owners a complete printer
dashboard in the Device tab out of the box.

src/slic3r/Utils/CrealityPrint.cpp

@@ -294,6 +294,36 @@ std::string CrealityPrint::query_boxes_info() const
     }
 }
 
+std::string CrealityPrint::get_print_host_webui(DynamicPrintConfig* config)
+{
+    // K-series printers (K2 / K2 Plus / K2 Pro) ship with Mainsail on port 4408.
+    // Port 80 hosts only the Creality control / upload API, which returns 404
+    // for unknown paths and therefore renders as a blank/404 page in Orca's
+    // Device WebView. Default to the Mainsail URL when the user hasn't
+    // explicitly set print_host_webui.
+    if (config == nullptr)
+        return {};
+
+    std::string explicit_url = config->opt_string("print_host_webui");
+    if (!explicit_url.empty())
+        return explicit_url;
+
+    std::string host = config->opt_string("print_host");
+    if (host.empty())
+        return {};
+
+    if (boost::algorithm::istarts_with(host, "http://"))
+        host = host.substr(7);
+    else if (boost::algorithm::istarts_with(host, "https://"))
+        host = host.substr(8);
+    if (auto slash = host.find('/'); slash != std::string::npos)
+        host = host.substr(0, slash);
+    if (auto colon = host.find(':'); colon != std::string::npos)
+        host = host.substr(0, colon);
+
+    return "http://" + host + ":4408/";
+}
+
 bool CrealityPrint::start_print(wxString &msg, const std::string &filename, const std::map<std::string, std::string>& extended_info) const
 {
     try {

src/slic3r/Utils/CrealityPrint.hpp

@@ -34,6 +34,10 @@ public:
     std::string query_boxes_info() const;
     std::string model_name() const;
 
+    // Mainsail on K-series printers listens on port 4408. Use that as the
+    // default Device-tab WebView URL when the user has not set print_host_webui.
+    static std::string get_print_host_webui(DynamicPrintConfig *config);
+
 protected:
     virtual void set_auth(Http& http) const;
 private:

src/slic3r/Utils/PrintHost.cpp

@@ -88,6 +88,10 @@ std::string PrintHost::get_print_host_webui(DynamicPrintConfig* config)
         webui_url = ElegooLink::get_print_host_webui(config);
         break;
     }
+    case htCrealityPrint: {
+        webui_url = CrealityPrint::get_print_host_webui(config);
+        break;
+    }
     default: break;
     }