Actions Passed to an Interact

This chapter describes the actions that can be issued to an interact’s main entry point. Interact actions are also generic in character, they could be issued to other plug-in types rather than just Image Effects, however they are not issued directly to an effect’s main entry point, they are rather issued to separate entry points which exist on specific ‘interact’ objects that a plugin may create.

For nearly all the actions the handle passed to to main entry point for an interact will be either NULL, or a value that should be cast to an OfxInteractHandle.

kOfxActionDescribeInteract

This action is the first action passed to an interact. It is where an interact defines how it behaves and the resources it needs to function. If not trapped, the default action is for the host to carry on as normal Note that the handle passed in acts as a descriptor for, rather than an instance of the interact.

Pre
  • The plugin has been loaded and the effect described.
Return
Parameters
  • handle: handle to the interact descriptor, cast to an OfxInteractHandle
  • inArgs: is redundant and is set to NULL
  • outArgs: is redundant and is set to NULL

kOfxActionCreateInstanceInteract

This action is the first action passed to an interact instance after its creation. It is there to allow a plugin to create any per-instance data structures it may need.

Pre
Post
  • the instance pointer will be valid until the kOfxActionDestroyInstance action is passed to the plug-in with the same instance handle
Return
Parameters
  • handle: handle to the interact instance, cast to an OfxInteractHandle
  • inArgs: is redundant and is set to NULL
  • outArgs: is redundant and is set to NULL

kOfxActionDestroyInstanceInteract

This action is the last passed to an interact’s instance before its destruction. It is there to allow a plugin to destroy any per-instance data structures it may have created.

Pre
Post
  • the instance pointer is no longer valid and any operation on it will be undefined
Return
To some extent, what is returned is moot, a bit like throwing an exception in a C++ destructor, so the host should continue destruction of the instance regardless
Parameters
  • handle: handle to the interact instance, cast to an OfxInteractHandle
  • inArgs: is redundant and is set to NULL
  • outArgs: is redundant and is set to NULL

kOfxInteractActionDraw

This action is issued to an interact whenever the host needs the plugin to redraw the given interact. The interact should issue any openGL calls it needs at this point.

Note that the interact may (in the case of custom parameter GUIS) or may not (in the case of image effect overlays) be required to swap buffers, that is up to the kind of interact.

Pre
  • kOfxActionCreateInstance has been called on the instance handle
  • the openGL context for this interact has been set
  • the projection matrix will correspond to the interact’s cannonical view
Return
Parameters

kOfxInteractActionPenMotion

This action is issued whenever the pen moves an the interact’s has focus. It should be issued whether the pen is currently up or down. No openGL calls should be issued by the plug-in during this action.

Pre
Post
  • if the instance returns kOfxStatOK the host should not pass the pen motion to any other interactive object it may own that shares the same view.
Return
  • kOfxStatOK the action was trapped and the host should not pass the event to other objects it may own
  • kOfxStatReplyDefault the action was not trapped and the host can deal with it if it wants
Parameters

kOfxInteractActionPenDown

This action is issued when a pen transitions for the ‘up’ to the ‘down’ state. No openGL calls should be issued by the plug-in during this action.

Pre
Post
  • if the instance returns kOfxStatOK, the host should not pass the pen motion to any other interactive object it may own that shares the same view.
Return
  • kOfxStatOK, the action was trapped and the host should not pass the event to other objects it may own
  • kOfxStatReplyDefault , the action was not trapped and the host can deal with it if it wants
Parameters

kOfxInteractActionPenUp

This action is issued when a pen transitions for the ‘down’ to the ‘up’ state. No openGL calls should be issued by the plug-in during this action.

Pre
Post
  • if the instance returns kOfxStatOK, the host should not pass the pen motion to any other interactive object it may own that shares the same view.
Return
  • kOfxStatOK, the action was trapped and the host should not pass the event to other objects it may own
  • kOfxStatReplyDefault , the action was not trapped and the host can deal with it if it wants
Parameters

kOfxInteractActionKeyDown

This action is issued when a key on the keyboard is depressed. No openGL calls should be issued by the plug-in during this action.

Pre
Post
  • if the instance returns kOfxStatOK, the host should not pass the pen motion to any other interactive object it may own that shares the same focus.
Return
  • kOfxStatOK , the action was trapped and the host should not pass the event to other objects it may own
  • kOfxStatReplyDefault , the action was not trapped and the host can deal with it if it wants
Parameters
  • handle: handle to an interact instance, cast to an OfxInteractHandle
  • inArgs: has the following properties on an image effect plugin
    • kOfxPropEffectInstance a handle to the effect for which the interact has been,
    • kOfxPropKeySym single integer value representing the key that was manipulated, this may not have a UTF8 representation (eg: a return key)
    • kOfxPropKeyString UTF8 string representing a character key that was pressed, some keys have no UTF8 encoding, in which case this is “”
    • kOfxPropTime the effect time at which changed occured
    • kOfxImageEffectPropRenderScale the render scale applied to any image fetched
  • outArgs: is redundant and is set to NULL

kOfxInteractActionKeyUp

This action is issued when a key on the keyboard is released. No openGL calls should be issued by the plug-in during this action.

Pre
Post
  • if the instance returns kOfxStatOK, the host should not pass the pen motion to any other interactive object it may own that shares the same focus.
Return
  • kOfxStatOK , the action was trapped and the host should not pass the event to other objects it may own
  • kOfxStatReplyDefault , the action was not trapped and the host can deal with it if it wants
Parameters
  • handle: handle to an interact instance, cast to an OfxInteractHandle
  • inArgs: has the following properties on an image effect plugin
    • kOfxPropEffectInstance a handle to the effect for which the interact has been,
    • kOfxPropKeySym single integer value representing the key that was manipulated, this may not have a UTF8 representation (eg: a return key)
    • kOfxPropKeyString UTF8 string representing a character key that was pressed, some keys have no UTF8 encoding, in which case this is “”
    • kOfxPropTime the effect time at which changed occured
    • kOfxImageEffectPropRenderScale the render scale applied to any image fetched
  • outArgs: is redundant and is set to NULL

kOfxInteractActionKeyRepeat

This action is issued when a key on the keyboard is repeated. No openGL calls should be issued by the plug-in during this action.

Pre
Post
  • if the instance returns kOfxStatOK, the host should not pass the pen motion to any other interactive object it may own that shares the same focus.
Return
  • kOfxStatOK , the action was trapped and the host should not pass the event to other objects it may own
  • kOfxStatReplyDefault , the action was not trapped and the host can deal with it if it wants
Parameters
  • handle: handle to an interact instance, cast to an OfxInteractHandle
  • inArgs: has the following properties on an image effect plugin
    • kOfxPropEffectInstance a handle to the effect for which the interact has been,
    • kOfxPropKeySym single integer value representing the key that was manipulated, this may not have a UTF8 representation (eg: a return key)
    • kOfxPropKeyString UTF8 string representing a character key that was pressed, some keys have no UTF8 encoding, in which case this is “”
    • kOfxPropTime the effect time at which changed occured
    • kOfxImageEffectPropRenderScale the render scale applied to any image fetched
  • outArgs: is redundant and is set to NULL

kOfxInteractActionGainFocus

This action is issued when an interact gains input focus. No openGL calls should be issued by the plug-in during this action.

Pre
Return
Parameters

kOfxInteractActionLoseFocus

This action is issued when an interact loses input focus. No openGL calls should be issued by the plug-in during this action.

Pre
Return
Parameters