FIX: STUDIO-3745 open gcode.3mf, unable export to file

Change-Id: Ib8a45cb38f28438ecc4d2a772f1437dbd324078a

src/slic3r/GUI/MainFrame.cpp

@@ -1866,7 +1866,7 @@ bool MainFrame::get_enable_print_status()
     }
     else if (m_print_select == eExportSlicedFile)
     {
-        if (!current_plate->is_slice_result_ready_for_print())
+        if (!current_plate->is_slice_result_ready_for_export())
         {
             enable = false;
         }
@@ -1889,7 +1889,7 @@ bool MainFrame::get_enable_print_status()
     }
     else if (m_print_select == eExportAllSlicedFile)
     {
-        if (!part_plate_list.is_all_slice_results_ready_for_print())
+        if (!part_plate_list.is_all_slice_result_ready_for_export())
         {
             enable = false;
         }

src/slic3r/GUI/PartPlate.cpp

@@ -4728,6 +4728,30 @@ bool PartPlateList::is_all_slice_results_ready_for_print() const
     return res;
 }
 
+//check whether all plates' slice result valid for export to file
+bool PartPlateList::is_all_slice_result_ready_for_export() const
+{
+	bool res = false;
+
+    for (unsigned int i = 0; i < (unsigned int) m_plate_list.size(); ++i) {
+        if (!m_plate_list[i]->empty()) {
+            if (m_plate_list[i]->is_all_instances_unprintable()) {
+				continue;
+			}
+            if (!m_plate_list[i]->is_slice_result_ready_for_print()) {
+				return false;
+			}
+        }
+        if (m_plate_list[i]->is_slice_result_ready_for_print()) {
+			if (!m_plate_list[i]->has_printable_instances()) {
+				return false;
+			}
+			res = true;
+		}
+    }
+
+    return res;
+}
 
 //check whether all plates ready for slice
 bool PartPlateList::is_all_plates_ready_for_slice() const

src/slic3r/GUI/PartPlate.hpp

@@ -411,6 +411,12 @@ public:
         return result;
     }
 
+    // check whether plate's slice result valid for export to file
+    bool is_slice_result_ready_for_export()
+    {
+        return is_slice_result_ready_for_print() && has_printable_instances();
+    }
+
     //invalid sliced result
     void update_slice_result_valid_state(bool valid = false);
 
@@ -775,6 +781,7 @@ public:
     bool is_all_slice_results_valid() const;
     bool is_all_slice_results_ready_for_print() const;
     bool is_all_plates_ready_for_slice() const;
+    bool is_all_slice_result_ready_for_export() const;
     void print() const;
 
     //get the all the sliced result