Change UI job's process() method to be protected, as it should have been

Also add some comments to the interface of Job class

src/slic3r/GUI/Jobs/ArrangeJob.hpp

@@ -36,6 +36,8 @@ protected:
 
     void on_exception(const std::exception_ptr &) override;
 
+    void process() override;
+
 public:
     ArrangeJob(std::shared_ptr<ProgressIndicator> pri, Plater *plater)
         : PlaterJob{std::move(pri), plater}
@@ -46,8 +48,6 @@ public:
         return int(m_selected.size() + m_unprintable.size());
     }
     
-    void process() override;
-    
     void finalize() override;
 };
 

src/slic3r/GUI/Jobs/FillBedJob.hpp

@@ -24,6 +24,7 @@ class FillBedJob : public PlaterJob
 protected:
 
     void prepare() override;
+    void process() override;
 
 public:
     FillBedJob(std::shared_ptr<ProgressIndicator> pri, Plater *plater)
@@ -35,8 +36,6 @@ public:
         return m_status_range;
     }
 
-    void process() override;
-
     void finalize() override;
 };
 

src/slic3r/GUI/Jobs/Job.hpp

@@ -50,10 +50,19 @@ protected:
     // Launched just before start(), a job can use it to prepare internals
     virtual void prepare() {}
 
+    // The method where the actual work of the job should be defined.
+    virtual void process() = 0;
+    
     // Launched when the job is finished. It refreshes the 3Dscene by def.
     virtual void finalize() { m_finalized = true; }
 
-    virtual void on_exception(const std::exception_ptr &) {}
+    // Exceptions occuring in process() are redirected from the worker thread
+    // into the main (UI) thread. This method is called from the main thread and
+    // can be overriden to handle these exceptions.
+    virtual void on_exception(const std::exception_ptr &eptr)
+    {
+        if (eptr) std::rethrow_exception(eptr);
+    }
    
 public:
     Job(std::shared_ptr<ProgressIndicator> pri);
@@ -65,8 +74,6 @@ public:
     Job &operator=(const Job &) = delete;
     Job &operator=(Job &&) = delete;
     
-    virtual void process() = 0;
-    
     void start();
     
     // To wait for the running job and join the threads. False is

src/slic3r/GUI/Jobs/RotoptimizeJob.hpp

@@ -48,6 +48,7 @@ class RotoptimizeJob : public PlaterJob
 protected:
 
     void prepare() override;
+    void process() override;
 
 public:
 
@@ -55,7 +56,6 @@ public:
         : PlaterJob{std::move(pri), plater}
     {}
 
-    void process() override;
     void finalize() override;
 
     static constexpr size_t get_methods_count() { return std::size(Methods); }

src/slic3r/GUI/Jobs/SLAImportJob.hpp

@@ -10,18 +10,16 @@ class SLAImportJob : public PlaterJob {
     
     std::unique_ptr<priv> p;
     
+protected:
+    void prepare() override;
+    void process() override;
+    void finalize() override;
+
 public:
     SLAImportJob(std::shared_ptr<ProgressIndicator> pri, Plater *plater);
     ~SLAImportJob();
 
-    void process() override;
-    
     void reset();
-    
-protected:
-    void prepare() override;
-    
-    void finalize() override;
 };
 
 }}     // namespace Slic3r::GUI