cookbook: Added example code for texture cross-fading
Added simple image viewer which loads image file names from a directory, displays the first one, then displays the next in the list with each key press. Uses the primitive fade front in/fade back out approach. Also adapted Emmanuele's example code which uses Cogl to produce a similar effect, but within a single texture. This code loads two images specified on the command line and cross-fades between them.
This commit is contained in:
Elliot Smith
174
doc/cookbook/examples/textures-crossfade.c
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174
doc/cookbook/examples/textures-crossfade.c
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#include <stdlib.h>
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#include <glib.h>
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#include <clutter/clutter.h>
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static guint stage_side = 600;
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static guint animation_duration_ms = 1500;
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static const ClutterColor stage_color = { 0x33, 0x33, 0x55, 0xff };
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typedef struct {
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ClutterActor *front;
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ClutterActor *back;
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ClutterState *transitions;
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GSList *image_paths;
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guint next_image_index;
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} State;
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static gboolean
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load_next_image (State *app)
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{
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/* don't do anything if already animating */
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ClutterTimeline *timeline = clutter_state_get_timeline (app->transitions);
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if (clutter_timeline_is_playing (timeline) == 1)
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{
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g_debug ("Animation is running already");
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return FALSE;
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}
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if (!app->next_image_index)
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app->next_image_index = 0;
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gpointer next = g_slist_nth_data (app->image_paths, app->next_image_index);
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if (next == NULL)
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return FALSE;
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gchar *image_path = (gchar *)next;
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g_debug ("Loading %s", image_path);
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CoglHandle *cogl_texture;
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cogl_texture = clutter_texture_get_cogl_texture (CLUTTER_TEXTURE (app->front));
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if (cogl_texture != NULL)
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{
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/* copy the current texture into the background */
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clutter_texture_set_cogl_texture (CLUTTER_TEXTURE (app->back), cogl_texture);
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/* make the back opaque and front transparent */
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clutter_state_warp_to_state (app->transitions, "show-back");
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}
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/* load the next image into the front */
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GError *error = NULL;
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clutter_texture_set_from_file (CLUTTER_TEXTURE (app->front),
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image_path,
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&error);
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if (error != NULL)
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{
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g_warning ("Error loading %s\n%s", image_path, error->message);
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g_error_free (error);
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return FALSE;
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}
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/* fade in the front texture and fade out the back texture */
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clutter_state_set_state (app->transitions, "show-front");
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app->next_image_index++;
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return TRUE;
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}
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static gboolean
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_key_pressed_cb (ClutterActor *actor,
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ClutterEvent *event,
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gpointer user_data)
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{
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State *app = (State *)user_data;
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load_next_image (app);
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return TRUE;
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}
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int
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main (int argc, char *argv[])
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{
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if (argc < 2)
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{
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g_print ("Usage: %s <image paths to load>\n", argv[0]);
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exit (EXIT_FAILURE);
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}
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State *app = g_new0 (State, 1);
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app->image_paths = NULL;
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/*
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* NB if your shell globs arguments to this program so argv
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* includes non-image files, they will fail to load and throw errors
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*/
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guint i;
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for (i = 1; i < argc; i++)
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app->image_paths = g_slist_append (app->image_paths, argv[i]);
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GError *error = NULL;
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/* UI */
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ClutterActor *stage;
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ClutterLayoutManager *layout;
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ClutterActor *box;
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clutter_init (&argc, &argv);
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stage = clutter_stage_get_default ();
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g_signal_connect (stage, "destroy", G_CALLBACK (clutter_main_quit), NULL);
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clutter_stage_set_title (CLUTTER_STAGE (stage), "cross-fade");
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clutter_actor_set_size (stage, stage_side, stage_side);
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clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);
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layout = clutter_bin_layout_new (CLUTTER_BIN_ALIGNMENT_CENTER,
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CLUTTER_BIN_ALIGNMENT_CENTER);
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box = clutter_box_new (layout);
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clutter_actor_set_size (box, stage_side, stage_side);
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app->back = clutter_texture_new ();
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clutter_texture_set_keep_aspect_ratio (CLUTTER_TEXTURE (app->back), TRUE);
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app->front = clutter_texture_new ();
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clutter_texture_set_keep_aspect_ratio (CLUTTER_TEXTURE (app->front), TRUE);
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clutter_container_add_actor (CLUTTER_CONTAINER (box), app->back);
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clutter_container_add_actor (CLUTTER_CONTAINER (box), app->front);
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clutter_container_add_actor (CLUTTER_CONTAINER (stage), box);
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/* animations */
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app->transitions = clutter_state_new ();
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clutter_state_set (app->transitions, NULL, "show-front",
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app->front, "opacity", CLUTTER_EASE_IN_CUBIC, 255,
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app->back, "opacity", CLUTTER_EASE_IN_CUBIC, 0,
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NULL);
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clutter_state_set (app->transitions, NULL, "show-back",
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app->front, "opacity", CLUTTER_LINEAR, 0,
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app->back, "opacity", CLUTTER_LINEAR, 255,
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NULL);
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clutter_state_set_duration (app->transitions,
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NULL,
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NULL,
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animation_duration_ms);
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/* display the next (first) image */
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load_next_image (app);
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/* key press displays the next image */
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g_signal_connect (stage,
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"key-press-event",
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G_CALLBACK (_key_pressed_cb),
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app);
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clutter_actor_show (stage);
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clutter_main ();
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g_slist_free (app->image_paths);
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g_object_unref (app->transitions);
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g_free (app);
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if (error != NULL)
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g_error_free (error);
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return EXIT_SUCCESS;
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}
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