Merge pull request #12412 from samcake/blue

Introduce task abort feature for early exit of task branch

libraries/render-utils/src/HighlightEffect.cpp

@@ -453,6 +453,10 @@ void SelectionToHighlight::run(const render::RenderContextPointer& renderContext
             }
         }
     }
+
+    if (numLayers == 0) {
+        renderContext->taskFlow.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 TaskFlow::reset() {
+    _doAbortTask = false;
+}
+
+void TaskFlow::abortTask() {
+    _doAbortTask = true;
+}
+
+bool TaskFlow::doAbortTask() const {
+    return _doAbortTask;
+}
+
+

libraries/task/src/task/Task.h

@@ -27,15 +27,44 @@ template <class JC> class JobT;
 template <class JC> class TaskT;
 class JobNoIO {};
 
+// Task Flow control class is a simple per value object used to communicate flow control commands trhough the graph of tasks.
+// From within the Job::Run function, you can access it from the JobCOntext and  issue commands which   will be picked up by the Task calling for the Job run.
+// This is first introduced to provide a way to abort all the work from within a task job. see the "abortTask" call
+class TaskFlow {
+public:
+    // A job that wants to abort the rest of the other jobs execution in a task would issue that call "abortTask" and let the task early exit for this run.
+    // All the varyings produced by the aborted branch of jobs are left unmodified.
+    void abortTask();
+
+    // called by the task::run to perform flow control
+    // This should be considered private but still need to be accessible from the Task<T> class
+    TaskFlow() = default;
+    ~TaskFlow() = default;
+    void reset();
+    bool doAbortTask() const;
+
+protected:
+    bool _doAbortTask{ false };
+};
+
+// JobContext class is the base calss for the context object which is passed through all the Job::run calls thoughout the graph of jobs
+// It is used to communicate to the job::run its context and various state information the job relies on.
+// It specifically provide access to:
+// - The taskFlow object allowing for messaging control flow commands from within a Job::run
+// - The current Config object attached to the Job::run currently called.
+// The JobContext can be derived to add more global state to it that Jobs can access
 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;
+
+    // Task flow control
+    TaskFlow taskFlow{};
+
+protected:
 };
 using JobContextPointer = std::shared_ptr<JobContext>;
 
@@ -308,6 +337,10 @@ public:
             if (config->alwaysEnabled || config->enabled) {
                 for (auto job : TaskConcept::_jobs) {
                     job.run(jobContext);
+                    if (jobContext->taskFlow.doAbortTask()) {
+                        jobContext->taskFlow.reset();
+                        return;
+                    }
                 }
             }
         }