Autoselect file-format: Split up long line and better documentation.

done as part of CURA-11957

plugins/DigitalLibrary/resources/qml/SaveProjectFilesPage.qml

@@ -208,7 +208,14 @@ Item
         anchors.rightMargin: UM.Theme.getSize("thin_margin").height
 
         enabled: UM.Backend.state == UM.Backend.Done
-        currentIndex: UM.Backend.state == UM.Backend.Done ? ((Cura.MachineManager.activeMachine.getOutputFileFormats.includes("application/x-makerbot") || Cura.MachineManager.activeMachine.getOutputFileFormats.includes("application/x-makerbot-sketch")) ? 1 : 0) : 2
+
+        // Pre-select the correct index, depending on the situation (see the model-property below):
+        // - Don't select any post-slice-file-format when the engine isn't done.
+        // - Choose either the S-series or the Makerbot-series of printers' format otherwise, depending on the active printer.
+        // This way, the user can just click 'save' without having to worry about wether or not the format is right.
+        property int isMakerbotFormat: Cura.MachineManager.activeMachine.getOutputFileFormats.includes("application/x-makerbot") || Cura.MachineManager.activeMachine.getOutputFileFormats.includes("application/x-makerbot-sketch")
+        property int isBackendDone: UM.Backend.state == UM.Backend.Done
+        currentIndex: isBackendDone ? (isMakerbotFormat ? 1 : 0) : 2
 
         textRole: "text"
         valueRole: "value"