Expose screenshooting as an interface, drop SIGUSR hack.

This pulls in a bit of extra infrastructure for discovering adertised objects on the
client side.

wayland-util.c

@@ -0,0 +1,83 @@
+#include <stdlib.h>
+#include "wayland.h"
+
+int wl_hash_insert(struct wl_hash *hash, struct wl_object *object)
+{
+	struct wl_object **objects;
+	uint32_t alloc;
+
+	if (hash->count == hash->alloc) {
+		if (hash->alloc == 0)
+			alloc = 16;
+		else
+			alloc = hash->alloc * 2;
+		objects = realloc(hash->objects, alloc * sizeof *objects);
+		if (objects == NULL)
+			return -1;
+
+		hash->objects = objects;
+		hash->alloc = alloc;
+	}
+
+	hash->objects[hash->count] = object;
+	hash->count++;
+
+	return 0;
+}
+
+struct wl_object *
+wl_hash_lookup(struct wl_hash *hash, uint32_t id)
+{
+	int i;
+
+	for (i = 0; i < hash->count; i++) {
+		if (hash->objects[i]->id == id)
+			return hash->objects[i];
+	}
+
+	return NULL;
+}
+
+void
+wl_hash_delete(struct wl_hash *hash, struct wl_object *object)
+{
+	/* writeme */
+}
+
+
+void wl_list_init(struct wl_list *list)
+{
+	list->prev = list;
+	list->next = list;
+}
+
+void
+wl_list_insert(struct wl_list *list, struct wl_list *elm)
+{
+	elm->prev = list;
+	elm->next = list->next;
+	list->next = elm;
+	elm->next->prev = elm;
+}
+
+void
+wl_list_remove(struct wl_list *elm)
+{
+	elm->prev->next = elm->next;
+	elm->next->prev = elm->prev;
+}
+
+int
+wl_list_length(struct wl_list *list)
+{
+	struct wl_list *e;
+	int count;
+
+	e = list->next;
+	while (e != list) {
+		e = e->next;
+		count++;
+	}
+
+	return count;
+}