Introducing a way to abort a task from one of its job, using it to skip highlight tasks if nothing to highlight

libraries/render-utils/src/HighlightEffect.cpp

@@ -453,6 +453,10 @@ void SelectionToHighlight::run(const render::RenderContextPointer& renderContext
             }
         }
     }
+
+    if (numLayers == 0) {
+        renderContext->abortTask();
+    }
 }
 
 void ExtractSelectionName::run(const render::RenderContextPointer& renderContext, const Inputs& inputs, Outputs& outputs) {

libraries/task/src/task/Task.cpp

@@ -0,0 +1,35 @@
+//
+//  Task.cpp
+//  task/src/task
+//
+//  Created by Sam Gateau on 2/14/2018.
+//  Copyright 2018 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+#include "Task.h"
+
+using namespace task;
+
+JobContext::JobContext(const QLoggingCategory& category) :
+    profileCategory(category) {
+    assert(&category);
+}
+
+JobContext::~JobContext() {
+}
+
+void JobContext::resetTaskFlow() {
+    _doAbortTask = false;
+}
+
+void JobContext::abortTask() {
+    _doAbortTask = true;
+}
+
+bool JobContext::doAbortTask() const {
+    return _doAbortTask;
+}
+
+

libraries/task/src/task/Task.h

@@ -29,13 +29,21 @@ class JobNoIO {};
 
 class JobContext {
 public:
-    JobContext(const QLoggingCategory& category) : profileCategory(category) {
-        assert(&category);
-    }
-    virtual ~JobContext() {}
+    JobContext(const QLoggingCategory& category);
+    virtual ~JobContext();
 
     std::shared_ptr<JobConfig> jobConfig { nullptr };
     const QLoggingCategory& profileCategory;
+
+    // control flow commands
+    void resetTaskFlow();
+    void abortTask();
+
+    // Check command flow
+    bool doAbortTask() const;
+
+protected:
+    bool _doAbortTask{ false };
 };
 using JobContextPointer = std::shared_ptr<JobContext>;
 
@@ -308,6 +316,10 @@ public:
             if (config->alwaysEnabled || config->enabled) {
                 for (auto job : TaskConcept::_jobs) {
                     job.run(jobContext);
+                    if (jobContext->doAbortTask()) {
+                        jobContext->resetTaskFlow();
+                        return;
+                    }
                 }
             }
         }