The Generic Instance Changed Action

	#include "ofxCore.h"
	#define kOfxActionInstanceChanged "OfxActionInstanceChanged" 

  • handle handle to the plug-in instance, cast to an OfxImageEffectHandle
  • inArgs has the following properties...
    • kOfxPropType - the type of the thing that changed which will be one of..
      • kOfxTypeParameter - indicating a parameter's value has changed in some way
      • kOfxTypeClip - a clip to an image effect has changed in some way (for Image Effect Plugins only)
    • kOfxPropName - the name of the thing that was changed in the instance
    • kOfxPropChangeReason - what triggered the change, which will be one of...
      • kOfxChangeUserEdited - the user or host changed the instance somehow and caused a change to something, this includes undo/redos, resets and loading values from files or presets,
      • kOfxChangePluginEdited - the plugin itself has changed the value of the instance in some action
      • kOfxChangeTime - the time has changed and this has affected the value of the object because it varies over time
    • kOfxPropTime - the effect time at which the chang occured (for Image Effect Plugins only)
    • kOfxImageEffectPropRenderScale - the render scale currently being applied to any image fetched from a clip (for Image Effect Plugins only)
  • outArgs is redundant and is set to NULL.


This action signals that something has changed in a plugin's instance, either by user action, the host or the plugin itself. All change actions are bracketed by a pair of kOfxActionBeginInstanceChanged and kOfxActionEndInstanceChanged actions. The inArgs property set is used to determine what was the thing inside the instance that was changed.


  • kOfxActionCreateInstance has been called on the instance handle,
  • kOfxActionBeginInstanceChanged has been called on the instance handle.


  • kOfxActionEndInstanceChanged will be called on the instance handle.

Return Values

  • kOfxStatOK, the action was trapped and all was well
  • kOfxStatReplyDefault, the action was ignored
  • kOfxStatErrFatal,
  • kOfxStatFailed, something went wrong, but no error code appropriate, the plugin should to post a message