Button Interaction (XForms (Forms Library) - Version 1.2 (Rev. 4) A Graphical User Interface Toolkit for X)

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### 16.3 Button Interaction

`FL_NORMAL_BUTTON`s, `FL_PUSH_BUTTON`s, `FL_RADIO_BUTTON`s, `FL_RETURN_BUTTON`s and `FL_HIDDEN_BUTTON`s are returned at the moment the user releases the mouse after having pressed it on the button. A `FL_MENU_BUTTON`, in contrast, is returned already on a mouse press. A `FL_INOUT_BUTTON` is returned both when the user presses it and when the user releases it. A `FL_TOUCH_BUTTON` is returned all the time as long as the user keeps the mouse button pressed while the mouse is on top of it. A `FL_RETURN_BUTTON` and a `FL_HIDDEN_RET_BUTTON` are also returned when the user presses the `<Return>` key.

As for other “active” objects, you can control under which conditions a button object gets returned or its callback invoked by using the function

    int fl_set_object_return(FL_OBJECT *obj, unsigned int when);

where reasonable values for `when` are

`FL_RETURN_NONE`

  Never return object or invoke callback.

`FL_RETURN_END_CHANGED`

  Return object or invoke callback when mouse button is released and at the same moment the state of the button changed.

`FL_RETURN_CHANGED`

  Return object or invoke callback whenever the state of the button changes.

`FL_RETURN_END`

  Return object or invoke callback when mouse button is released

`FL_RETURN_ALWAYS`

  Return object or invoke callback on all of the above condtions.

Most buttons will always return `FL_RETURN_END` and `FL_RETURN_CHANGED` at the same time. Exceptions are `FL_INOUT_BUTTON`s and `FL_TOUCH_BUTTON`s. The former returns `FL_RETURN_CHANGED` when pushed and both `FL_RETURN_END` and `FL_RETURN_CHANGED` together when released. `FL_TOUCH_BUTTON`s return when pressed, then `FL_RETURN_CHANGED` at regular time intervals while being pressed and finally `FL_RETURN_END` when released.

See demo `butttypes.c` for a feel of the different button types.

Next: Other Button Routines, Previous: Button Types, Up: Part III Button-like Objects [Contents][Index]