~~Title: Evas Events~~
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===== Evas Events =====

Evas events happen on a canvas as a whole. This kind of events are too
low-level for writing applications and are most often used when writing the
graphical toolkit itself.

=== Table of Contents ===

  * [[#Adding_Callbacks_to_Canvases:_evas_event_callback_add/del</a>|Adding Callbacks to Canvases: evas_event_callback_add/del]]
  * [[#Types_of_Evas_Events|Types of Evas Events]]

=== Related Info ===

  * [[https://build.enlightenment.org/job/nightly_efl_gcc_x86_64/lastSuccessfulBuild/artifact/doc/html/group__Evas__Canvas__Events.html|Canvas Events API]] ([[https://build.enlightenment.org/job/nightly_efl_gcc_x86_64/lastSuccessfulBuild/artifact/doc/html/group__Evas.html#gad64cde0da38a60e7cb7905b3ab216968|Evas API]])
  * [[https://build.enlightenment.org/job/nightly_efl_gcc_x86_64/lastSuccessfulBuild/artifact/doc/html/Example_Evas_Events.html|Evas events example]]

==== Adding Callbacks to Canvases: evas_event_callback_add/del ====

The callbacks are added with ''evas_event_callback_add()''. Its prototype is

<code c>
void evas_event_callback_add(Evas*              e,
                             Evas_Callback_Type type,
                             Evas_Event_Cb      func,
                             const void*        data
                            )
</code>

  * ''e'' is the evas canvas on which the events happen. If needed, it can be
obtained from an Evas_Object through the ''evas_object_evas_get()'' function.
  * ''type'' is the type of event that triggers the callback (the list is in the next section).
  * ''func'' is the function that is called.
  * ''data'' is a pointer to additional data that is given as an argument to the callback. It is optional and ''NULL'' is an acceptable value.

The type of the callback function is defined as follows.

<code c>
void (* Evas_Event_Cb) (void *data, Evas *e, void *event_info)
</code>

The callback function definition is similar to

<code c>
void some_evas_object_event_cb(void *data, Evas *e, void *event_info);
</code>

  * ''data'' is the same as the data which was given as the parameter to ''evas_event_callback_add()''.
  * ''e'' is the canvas on which the event occurred.
  * ''event_info'' is data which depends on the object type and the event at play. The documentation must be read for each such event.

==== Types of Evas Events ====

The values are defined from the ''Evas_Callback_Type'' enum. Some of them are
not used for ''evas_event_callback_add()'' but are used in the previous
section.

  * ''EVAS_CALLBACK_CANVAS_FOCUS_IN        '':       Image has been preloaded.
  * ''EVAS_CALLBACK_CANVAS_FOCUS_OUT       '':       Canvas got focus as a whole.
  * ''EVAS_CALLBACK_RENDER_FLUSH_PRE       '':       Canvas lost focus as a whole.
  * ''EVAS_CALLBACK_RENDER_FLUSH_POST      '':       Called just before rendering is updated on the canvas target.
  * ''EVAS_CALLBACK_CANVAS_OBJECT_FOCUS_IN '':       Called just after rendering is updated on the canvas target.
  * ''EVAS_CALLBACK_CANVAS_OBJECT_FOCUS_OUT'':       Canvas object got focus.

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