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/**
* Example of basic usage of Ecore-Evas and transparent windows.
*
* The evas-buffer-simple.c example shows how to manually create and
* manage buffers, but mentioned that real code would use higher level
* functionality from Ecore's Ecore-Evas submodule. This example
* shows the use of that submodule to create a simple Evas canvas.
*
* This example also demonstrates how to create transparent windows with
* Evas. Like in most other graphics software, transparency and
* translucency is calculated using an integer parameter called an
* 'alpha channel'. Support for alpha transparency is platform
* dependent, and even where it is supported it may not be needed,
* so Ecore-Evas provides a simple API to turn it on and off, which
* this example will demonstrate by allowing it to be toggled via
* the 'n' and 'm' keys on the keyboard.
*
* The keyboard input will introduce 'event handling' in Ecore-Evas, but
* only briefly - we'll be exploring event handling in later examples
* more deeply.
*
* @verbatim
* gcc -o evas-transparent evas-transparent.c `pkg-config --libs --cflags evas ecore ecore-evas eina`
* @endverbatim
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#else
#define PACKAGE_EXAMPLES_DIR "."
#endif
#include <Ecore.h>
#include <Ecore_Evas.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define WIDTH (640)
#define HEIGHT (480)
static const char *commands = \
"commands are:\n"
"\tn - turn on alpha"
"\tm - turn off alpha"
"\th - print help\n";
struct exemple_data
{
Ecore_Evas *ee;
Evas *evas;
Evas_Object *bg;
};
static struct exemple_data d;
/* Keyboard event callback routine, to enable toggling transparency on
* and off.
*/
static void
_on_keydown(void *data EINA_UNUSED,
Evas *evas EINA_UNUSED,
Evas_Object *o EINA_UNUSED,
void *einfo)
{
Evas_Event_Key_Down *ev = einfo;
if (strcmp(ev->key, "h") == 0)
{
/* h - print help */
printf("%s", commands);
return;
}
if (strcmp(ev->key, "n") == 0)
{
/* n - turn alpha transparency on */
ecore_evas_alpha_set(d.ee, EINA_TRUE);
printf("turn on alpha\n");
return;
}
if (strcmp(ev->key, "m") == 0)
{
/* m - turn alpha transparency off */
ecore_evas_alpha_set(d.ee, EINA_FALSE);
printf("turn off alpha\n");
return;
}
}
static void
_on_delete(Ecore_Evas *ee EINA_UNUSED)
{
/* Communicate to ecore that the application is finished. Calling
* this routine allows any pending events to get processed and allow
* the main loop to finish the current iteration.
*/
ecore_main_loop_quit();
}
int
main(void)
{
/* In other examples, evas_init() has been used to turn Evas on. In this
* example we're using Ecore-Evas' init routine, which takes care of
* bringing up Evas.
*/
if (!ecore_evas_init())
return EXIT_FAILURE;
/* In the evas-buffer-simple.c example, we coded our own
* create_canvas() routine. Here we make use of Ecore-Evas's
* ecore_evas_new() routine to do it. The first argument of this
* function is used to specify the name of an engine we wish to use;
* by passing NULL instead, we are requesting a window with an Evas
* canvas using the first engine available.
*
* The next arguments set the canvas's position to 0,0 and its
* height and width to our desired size.
*
* The last parameter for ecore_evas_new() allows setting extra
* options, but for this example we don't need anything special
* so just pass NULL.
*/
d.ee = ecore_evas_new(NULL, 0, 0, WIDTH, HEIGHT, NULL);
if (!d.ee)
goto panic;
/* Like other windowing systems, Ecore-Evas provides hooks for a
* number of different events. We can register our own functions to
* be called when the events occur in our window. Here we'll register
* a callback to be triggered when the window is closed.
*/
ecore_evas_callback_delete_request_set(d.ee, _on_delete);
/* As in evas-buffer-simple.c, we need to explicitly 'unhide' our
* Evas objects. But here we'll use the Ecore-Evas API to do this,
* as it also manages some of the underlying device state.
*/
ecore_evas_show(d.ee);
/* Retrieve a pointer to the canvas we created. */
d.evas = ecore_evas_get(d.ee);
/* Add a black background rectangle */
d.bg = evas_object_rectangle_add(d.evas);
evas_object_color_set(d.bg, 0, 0, 0, 0);
evas_object_show(d.bg);
/* Callbacks can also be set on Evas objects. We'll add a keyboard
* handler routine to the background rectangle, for processing user
* key hits.
*/
evas_object_focus_set(d.bg, EINA_TRUE);
evas_object_event_callback_add(d.bg, EVAS_CALLBACK_KEY_DOWN,
_on_keydown, NULL);
/* Run the application until ecore_main_loop_quit() gets called by
* our _on_delete() handler. While this function is active, it will
* repeatedly call ecore_main_loop_iterate() to iterate through
* various internal processes, checking for keyboard input, updating
* the screen as needed, and so forth.
*/
ecore_main_loop_begin();
/* With the application finished, we now direct the Ecore and Evas
* libraries to perform final cleanup and terminate the system.
*/
ecore_evas_shutdown();
return 0;
panic:
fprintf(stderr, "You got to have at least one evas engine built and linked"
" up to ecore-evas for this example to run properly.\n");
return -2;
}
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