SoMField(3)

NAME
SoMField - The SoMField class is the base class for fields which can contain multiple values.

SYNOPSIS

#include <Inventor/fields/SoMField.h>

Inherits SoField.

Inherited by SoMFBool, SoMFColor, SoMFColorRGBA, SoMFDouble, SoMFEngine, SoMFEnum, SoMFFloat, SoMFInt32, SoMFMatrix, SoMFName, SoMFNode, SoMFPath, SoMFPlane, SoMFRotation, SoMFShort, SoMFString, SoMFTime, SoMFUInt32, SoMFUShort, SoMFVec2b, SoMFVec2d, SoMFVec2f, SoMFVec2i32, SoMFVec2s, SoMFVec3b, SoMFVec3d, SoMFVec3f, SoMFVec3i32, SoMFVec3s, SoMFVec4b, SoMFVec4d, SoMFVec4f, SoMFVec4i32, SoMFVec4s, SoMFVec4ub, SoMFVec4ui32, and SoMFVec4us.

  Public Member Functions
virtual ~SoMField ()
int getNum (void) const
void setNum (const int num)
virtual void deleteValues (int start, int num=-1)
virtual void insertSpace (int start, int num)
SbBool set1 (const int index, const char *const valuestring)
void get1 (const int index, SbString &valuestring)
virtual void enableDeleteValues (void)
virtual SbBool isDeleteValuesEnabled (void) const

  Static Public Member Functions
static SoType getClassTypeId (void)
static void atexit_cleanup (void)
static void initClass (void)

  Protected Member Functions
SoMField (void)
virtual void makeRoom (int newnum)
virtual SoNotRec createNotRec (SoBase *container)
void setChangedIndex (const int chgidx)
void setChangedIndices (const int chgidx=-1, const int numchgind=0)

  Protected Attributes
int num
int maxNum
SbBool userDataIsUsed

  Additional Inherited Members

Detailed Description

The SoMField class is the base class for fields which can contain multiple values. All field types which may contain more than one member value inherits this class. SoMField is an abstract class.

Use setValue(), setValues() or set1Value() to set the values of fields inheriting SoMField, and use getValues() or the index operator [] to read values. Example code:

SoText2 * textnode = new SoText2;
textnode->ref();
// Setting multi-field values. /////////////////////////////
// Set the first value of the SoMFString field of the SoText2 node.
// The field array will be truncated to only contain this single value.
textnode->string.setValue("Morten");
// Full contents of the SoMFString is: [ "Morten" ]
// The setValue() method and the = operator is interchangeable,
// so this code line does the same as the previous line.
textnode->string = "Peder";
// Full contents of the SoMFString is now: [ "Peder" ]
// Set the value at index 2. If the field value array contained
// less than 3 elements before this call, first expand it to contain
// 3 elements.
textnode->string.set1Value(2, "Lars");
// Full contents of the SoMFString is: [ "Peder", <undefined>, "Lars" ]
// This sets 3 values of the array, starting at index 5. If the
// array container had less than 8 elements before the setValues()
// call, the array will first be expanded.
SbString s[3] = { "Eriksen", "Blekken", "Aas" };
textnode->string.setValues(5, sizeof(s) / sizeof(s[0]), s);
// Full contents of the SoMFString is now:
//     [ "Peder", <undefined>, "Lars", <undefined>, <undefined>,
//       "Eriksen", "Blekken", "Aas" ]
// Note also that the setValues() call will *not* truncate a field
// container if you use it to change a subset at the start:
SbString n[4] = { "Dixon", "Adams", "Bould", "Winterburn" };
textnode->string.setValues(0, sizeof(n) / sizeof(n[0]), n);
// Full contents of the SoMFString is now:
//     [ "Dixon", "Adams", "Bould", "Winterburn", <undefined>,
//       "Eriksen", "Blekken", "Aas" ]
// Inspecting multi-field values. //////////////////////////
// This will read the second element (counting from zero) if the
// multivalue field and place it in "val".
SbString val = textnode->string[2];
// Gives us a pointer to the array which the multiple-value field
// is using to store the values. Note that the return value is
// "const", so you can only read from the array, not write to
// it.
const SbString * vals = textnode->string.getValues(0);
// Modifying multi-field values. ///////////////////////////
// You can of course modify multifield-values by using the set-
// and get-methods shown above, but when you're working with
// big sets of data, this will be ineffective. Then use this
// technique instead:
SbString * modvals = textnode->string.startEditing();
// ... lots of modifications to the "modvals" array here ...
// Calling the finishEditing() method is necessary for the
// scene graph to be updated (and re-rendered).
textnode->string.finishEditing();

The reason it is more effective to wrap many modifications within startEditing() / finishEditing() is because we avoid the stream of notification messages which would otherwise be sent for each and every modification done. Instead there will just be a single notification about the changes, triggered by the finishEditing() call.

The correct manner in which to pre-allocate a specific number of field values in one chunk is to use the SoMField::setNum() method, for instance in advance of using the startEditing() and finishEditing() methods. The field values will be uninitialized after expanding the field with the setNum() call.

Be aware that your application code must be careful to not do silly things during a setValues()-triggered notification. If you have code that looks for instance like this:

// update set of coordinate indices at the start of e.g.
// an SoIndexedFaceSet's coordIndex field..
ifs->coordIndex.setValues(0, runner->numIndices, runner->indices);
// ..then truncate to make sure it's the correct size.
ifs->coordIndex.setNum(runner->numIndices);

As setValues() might leave some elements at the end of the array that typically can be invalid indices after the first statement is executed, something can go wrong during notification if you have application code monitoring changes, and the application code then for instance triggers an action or something that tries to use the coordIndex field before it is updated to its correct size with the setNum() call.

(Notification can in this case, as always, be temporarily disabled to be on the safe side:

somefield.enableNotify(FALSE);
somefield.setValues(...);
somefield.setNum(...);
somefield.enableNotify(TRUE);
somefield.touch();

This will guarantee that the setValues() and setNum() pair will be executed as an atomic operation.)

When nodes, engines or other types of field containers are written to file, their multiple-value fields are written to file in this format:

containerclass {
  fieldname [ value0, value1, value2, ...]
  ...
}

..like this, for instance, a Coordinate3 node providing 6 vertex coordinates in the form of SbVec3f values in its 'point' field for e.g. a faceset, lineset or pointset:

Coordinate3 {
   point [
      -1 1 0, -1 -1 0, 1 -1 0,
      0 2 -1, -2 0 -1, 0 -2 -1,
   ]
}

Some fields support application data sharing through a setValuesPointer() method. setValuesPointer() makes it possible to set the data pointer directly in the field. Normally (when using setValues()), Coin makes a copy of your data, so this method can be very useful if your application needs the data internally and you're just using Coin for the visualization. Example code:

myapp->calculateCoordinates(SOME_LARGE_VALUE);
SbVec3f * mycoords = myapp->getCoordinates();
SoCoordinate3 * mynode = myapp->getCoordinateNode();
mynode->point.setValuesPointer(SOME_LARGE_VALUE, mycoords);

Be aware that your field should be a read-only field when you set the data like this. If you write to the field, the values in your application array will be overwritten. If you append values to the field, a new array will be allocated, and the data will be copied into it before appending the new values. The array pointer will then be discarded.

Also note that whenever you change some value(s) in the array, you must manually notify Coin about this by calling SoField::touch(). For our example:

SbVec3f * mycoords = myapp->getCoordinate();
myapp->updateCoordinate(mycoords);
SoCoordinate3 * mynode = myapp->getCoordinateNode();
mynode->point.touch(); // this will notify Coin that field has changed

You can use SoMField::enableDeleteValues() to make Coin delete the array for you when the field is destructed or the array pointer is discarded because it isn't needed anymore (e.g. when the array size is changed). The array will be deleted using the C++ delete[] operator, so if you use it, your array must be allocated using the C++ new[] operator.

SoMField::enableDeleteValues() is supported only to be compatible with later versions of TGS Inventor and we don't recommend using it. It can have undefined results on the Microsoft Windows platform. Allocating memory in the application and destructing it in a DLL can be a bad thing, causing mysterious crashes, if you're not very careful about how your application and DLLs are linked to the underlying C library.

See also
    SoSField

Constructor & Destructor Documentation

  SoMField::~SoMField () [virtual]
Destructor in SoMField does nothing. Resource deallocation needs to be done from subclasses.

  SoMField::SoMField (void) [protected]
Constructor. Initializes number of values in field to zero.

Member Function Documentation

  SoType SoMField::getClassTypeId (void) [static]
Returns a unique type identifier for this field class.

See also
    getTypeId(), SoType

  int SoMField::getNum (void) const [inline]
Returns number of values in this field.

  void SoMField::setNum (const int numarg)
Set number of values to num.

If the current number of values is larger than num, the array of values will be truncated from the end. But if num is larger, the array will automatically be expanded (and random values will be set for the new array items).

  void SoMField::deleteValues (int start, int numarg = -1) [virtual]
Remove value elements from index start up to and including index start + num - 1.

Elements with indices larger than the last deleted element will be moved downwards in the value array.

If num equals -1, delete from index start and to the end of the array.

Reimplemented in SoMFPath, SoMFNode, and SoMFEngine.

  void SoMField::insertSpace (int start, int numarg) [virtual]
Insert num 'slots' for new value elements from start. The elements already present from start will be moved 'upward' in the extended array.

Reimplemented in SoMFPath, SoMFNode, and SoMFEngine.

  SbBool SoMField::set1 (const int index, const char *const valuestring)
Set the value at index to the value contained in valuestring. Returns TRUE if a valid value for this field can be extracted from valuestring, otherwise FALSE.

If index is larger than the current number of elements in the field, this method will automatically expand the field to accommodate the new value.

  void SoMField::get1 (const int index, SbString & valuestring)
Return the value at index in the valuestring string.

  void SoMField::initClass (void) [static]
Internal method called upon initialization of the library (from SoDB::init()) to set up the type system.

  void SoMField::enableDeleteValues (void) [virtual]
Can be used to make Coin delete the array pointer set through a setValuesPointer() call. See SoMField documentation for information about the setValuesPointer() function.

This method is a TGS extension (introduced in TGS OIV v3.0) and is supported only for compatibility. We suggest that you don't use it since it can lead to hard-to-find bugs.

Since
    Coin 2.0

    TGS Inventor 3.0

  SbBool SoMField::isDeleteValuesEnabled (void) const [virtual]
Returns whether SoMField::enableDeleteValues() has been called on a field. The result is only valid if setValuesPointer() has been called on the field first.

This method is a TGS extension (introduced in TGS OIV v3.0) and is supported only for compatibility. We suggest that you don't use it since it can lead to hard-to-find bugs.

Since
    Coin 2.0

    TGS Inventor 3.0

  void SoMField::makeRoom (int newnum) [protected], [virtual]
Make room in the field to store newnum values.

Member Data Documentation

  int SoMField::num [protected]
Number of available values.

  int SoMField::maxNum [protected]
Number of array 'slots' allocated for this field.

  SbBool SoMField::userDataIsUsed [protected]
Is TRUE if data have been set through a setValuesPointer() call and set to FALSE through a enableDeleteValues() call.

Author

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