ENH: add single-time handling to timeSelector

- the timeSelector is often used to select single or multiple times
  (eg, for post-processing). However, there are a few applications
  where only a *single* time should be selected and set.

  These are now covered by this type of use:

      timeSelector::addOptions_singleTime();  // Single-time options
      ...
      // Allow override of time from specified time options, or no-op
      timeSelector::setTimeIfPresent(runTime, args);

   In some cases, if can be desirable to force starting from the
   initial Time=0 when no time options have been specified:

      // Set time from specified time options, or force start from Time=0
      timeSelector::setTimeIfPresent(runTime, args, true);

   These changes make a number of includes redundant:

     * addTimeOptions.H
     * checkConstantOption.H
     * checkTimeOption.H
     * checkTimeOptions.H
     * checkTimeOptionsNoConstant.H

ENH: add time handling to setFields, setAlphaField (#3143)

    Co-authored-by: Johan Roenby <>

STYLE: replace instant("constant") with instant(0, "constant")

- avoids relying on atof parse behaviour returning zero

applications/utilities/preProcessing/setAlphaField/setAlphaField.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 DHI
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2024 OpenCFD Ltd.
     Copyright (C) 2017-2020 German Aerospace Center (DLR)
     Copyright (C) 2020 Johan Roenby
 -------------------------------------------------------------------------------
@@ -39,6 +39,7 @@ Description
 \*---------------------------------------------------------------------------*/
 
 #include "fvCFD.H"
+#include "timeSelector.H"
 
 #include "triSurface.H"
 #include "triSurfaceTools.H"
@@ -139,6 +140,10 @@ void setAlpha
 
 int main(int argc, char *argv[])
 {
+    argList::noFunctionObjects();           // Never use function objects
+
+    timeSelector::addOptions_singleTime();  // Single-time options
+
     argList::addNote
     (
         "Uses cutCellIso to create a volume fraction field from an "
@@ -151,9 +156,14 @@ int main(int argc, char *argv[])
         "file",
         "Alternative setAlphaFieldDict dictionary"
     );
+
     #include "addRegionOption.H"
     #include "setRootCase.H"
     #include "createTime.H"
+
+    // Set time from specified time options, or no-op
+    timeSelector::setTimeIfPresent(runTime, args);
+
     #include "createNamedMesh.H"
 
     const word dictName("setAlphaFieldDict");

applications/utilities/preProcessing/setFields/setFields.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2022-2023 OpenCFD Ltd.
+    Copyright (C) 2022-2024 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -36,6 +36,7 @@ Description
 \*---------------------------------------------------------------------------*/
 
 #include "argList.H"
+#include "timeSelector.H"
 #include "Time.H"
 #include "fvMesh.H"
 #include "faMesh.H"
@@ -656,6 +657,10 @@ struct setAreaField
 
 int main(int argc, char *argv[])
 {
+    argList::noFunctionObjects();           // Never use function objects
+
+    timeSelector::addOptions_singleTime();  // Single-time options
+
     argList::addNote
     (
         "Set values on a selected set of cells/patch-faces via a dictionary"
@@ -670,8 +675,15 @@ int main(int argc, char *argv[])
     );
 
     #include "addRegionOption.H"
+
+    // -------------------------
+
     #include "setRootCase.H"
     #include "createTime.H"
+
+    // Set time from specified time options, or no-op
+    timeSelector::setTimeIfPresent(runTime, args);
+
     #include "createNamedMesh.H"
 
     autoPtr<faMesh> faMeshPtr;