# event handler functions

Prototype of functions which may be used as event handler.

## Calling Sequence

    event_handler_function(win,x,y,ibut)

## Arguments

win

  window number where the event had occurred.

x

  X coordinate in pixels of the mouse pointer when the events occurred.

y

  Y coordinate in pixels of the mouse pointer when the events occurred.

ibut

  number corresponding to the event type.

## Description

When the event handler mode is enable, Scilab will call the specified event handler function each time an event occures in the graphic window. The event handler function must comply with the above prototype. Each time an event occurred, the function is called and its four parameters are set accordingly to the window number, mouse position and type of event.

The `ibut` parameter takes one of the following value depending on event type:

ibut==0

  Left mouse button has been pressed

ibut==1

  Middle mouse button has been pressed

ibut==2

  Right mouse button has been pressed

ibut==3

  Left mouse button has been clicked

ibut==4

  Middle mouse button has been clicked

ibut==5

  Right mouse button has been clicked

ibut==10

  Left mouse button has been double-clicked

ibut==11

  Middle mouse button has been double-clicked

ibut==12

  Right mouse button has been double-clicked

ibut==-5

  Left mouse button has been released

ibut==-4

  Middle mouse button has been released

ibut==-3

  Right mouse button has been released

ibut==-1

  mouse pointer has moved

ibut > =32

  key with ascii code ascii(ibut) has been pressed

ibut < =-32

  key with ascii code ascii(-ibut) has been released

ibut > =1000+32

  key with ascii code ascii(ibut-1000) has been pressed while CTRL key pressed

ibut==-1000

  graphic window has been closed

For example, let say that the name of the event handler function is fooHandler for window number 0. A left click in the window at position [100,150] (in pixels) will be equivalent as calling fooHandler( 0, 100, 150, 3 ).

See figure_properties or seteventhandler for information on how to specify the event_handler name.

## Examples

    function my_eventhandler(win,x,y,ibut)
      if ibut==-1000 then return,end
      [x,y]=xchange(x,y,'i2f')
      xinfo(msprintf('Event code %d at mouse position is (%f,%f)',ibut,x,y))
    endfunction

    plot2d()
    fig = gcf() ;
    fig.event_handler = 'my_eventhandler' ;
    fig.event_handler_enable = "on" ;
    //now:
    //   -  move the mouse over the graphic window
    //   -  press and release keys shifted or not with Ctrl pressed or not
    //   -  press button, wait a little release
    //   -  press and release button
    //   -  double-click button

    fig.event_handler_enable = "off" ; //suppress the event handler

## See Also

- figure_properties
- seteventhandler
- xgetmouse
- xclick