WIP: SLA support "Generate points" and "Apply Changes" will reslice

just the selected object.
Added "Host upload active" check on background processing state.
Documented requirements on "update_background_process" to
control the upcoming single "Slice Now" / "Export" button.

src/slic3r/GUI/BackgroundSlicingProcess.cpp

@@ -196,6 +196,7 @@ void BackgroundSlicingProcess::thread_proc()
 		} catch (...) {
 			error = "Unknown C++ exception.";
 		}
+		m_print->finalize();
 		lck.lock();
 		m_state = m_print->canceled() ? STATE_CANCELED : STATE_FINISHED;
 		if (m_print->cancel_status() != Print::CANCELED_INTERNAL) {
@@ -362,6 +363,12 @@ Print::ApplyStatus BackgroundSlicingProcess::apply(const Model &model, const Dyn
 	return invalidated;
 }
 
+void BackgroundSlicingProcess::set_task(const PrintBase::TaskParams &params)
+{
+	assert(m_print != nullptr);
+	m_print->set_task(params);
+}
+
 // Set the output path of the G-code.
 void BackgroundSlicingProcess::schedule_export(const std::string &path)
 { 

src/slic3r/GUI/BackgroundSlicingProcess.hpp

@@ -78,6 +78,9 @@ public:
 	// Apply config over the print. Returns false, if the new config values caused any of the already
 	// processed steps to be invalidated, therefore the task will need to be restarted.
 	Print::ApplyStatus apply(const Model &model, const DynamicPrintConfig &config);
+	// After calling the apply() function, set_task() may be called to limit the task to be processed by process().
+	// This is useful for calculating SLA supports for a single object only.
+	void 		set_task(const PrintBase::TaskParams &params);
 	// After calling apply, the empty() call will report whether there is anything to slice.
 	bool 		empty() const;
 	// Validate the print. Returns an empty string if valid, returns an error message if invalid.
@@ -94,6 +97,7 @@ public:
 	void reset_export();
 	// Once the G-code export is scheduled, the apply() methods will do nothing.
 	bool is_export_scheduled() const { return ! m_export_path.empty(); }
+	bool is_upload_scheduled() const { return ! m_upload_job.empty(); }
 
 	enum State {
 		// m_thread  is not running yet, or it did not reach the STATE_IDLE yet (it does not wait on the condition yet).

src/slic3r/GUI/Plater.cpp

@@ -2032,6 +2032,13 @@ unsigned int Plater::priv::update_background_process(bool force_validation)
 		wxQueueEvent(GUI::wxGetApp().mainframe->m_plater, evt.Clone());
 	}
 
+    //FIXME update "Slice Now / Schedule background process"
+    //background_process.is_export_scheduled() - byl zavolan "Export G-code", background processing ma jmeno export souboru
+    //background_process.is_upload_scheduled() - byl zavolan "Send to OctoPrint", jeste nebylo doslajsovano (pak se preda upload fronte a background process zapomene)
+    //background_process.empty() - prazdna plocha
+    // pokud (invalidated != Print::APPLY_STATUS_UNCHANGED) a ! background_process.empty() -> je neco ke slajsovani (povol tlacitko)
+    // pokud (return_state & UPDATE_BACKGROUND_PROCESS_INVALID) != 0 -> doslo k chybe (gray out "Slice now")
+
     return return_state;
 }
 
@@ -2999,6 +3006,32 @@ void Plater::reslice()
     this->p->restart_background_process(state | priv::UPDATE_BACKGROUND_PROCESS_FORCE_RESTART);
 }
 
+void Plater::reslice_SLA_supports(const ModelObject &object)
+{
+    //FIXME Don't reslice if export of G-code or sending to OctoPrint is running.
+    // bitmask of UpdateBackgroundProcessReturnState
+    unsigned int state = this->p->update_background_process(true);
+    if (state & priv::UPDATE_BACKGROUND_PROCESS_REFRESH_SCENE)
+        this->p->view3D->reload_scene(false);
+
+	if (this->p->background_process.empty() || (state & priv::UPDATE_BACKGROUND_PROCESS_INVALID))
+        // Nothing to do on empty input or invalid configuration.
+        return;
+
+    // Limit calculation to the single object only.
+    PrintBase::TaskParams task;
+    task.single_model_object = object.id();
+    // If the background processing is not enabled, calculate supports just for the single instance.
+    // Otherwise calculate everything, but start with the provided object.
+	if (!this->p->background_processing_enabled()) {
+		task.single_model_instance_only = true;
+		task.to_object_step = slaposBasePool;
+	}
+    this->p->background_process.set_task(task);
+    // and let the background processing start.
+    this->p->restart_background_process(state | priv::UPDATE_BACKGROUND_PROCESS_FORCE_RESTART);
+}
+
 void Plater::send_gcode()
 {
     if (p->model.objects.empty()) { return; }

src/slic3r/GUI/Plater.hpp

@@ -19,6 +19,7 @@ class wxString;
 namespace Slic3r {
 
 class Model;
+class ModelObject;
 class Print;
 class SLAPrint;
 
@@ -145,6 +146,7 @@ public:
     void export_amf();
     void export_3mf(const boost::filesystem::path& output_path = boost::filesystem::path());
     void reslice();
+    void reslice_SLA_supports(const ModelObject &object);
     void changed_object(int obj_idx);
     void fix_through_netfabb(const int obj_idx, const int vol_idx = -1);
     void send_gcode();