Flesh out wayland backend somewhat, add example

include/wlr/common/list.h

@@ -0,0 +1,31 @@
+#ifndef _WLR_LIST_H
+#define _WLR_LIST_H
+
+#include <stddef.h>
+
+typedef struct {
+	size_t capacity;
+	size_t length;
+	void **items;
+} list_t;
+
+list_t *list_create(void);
+void list_free(list_t *list);
+void list_foreach(list_t *list, void (*callback)(void* item));
+void list_add(list_t *list, void *item);
+void list_push(list_t *list, void *item);
+void list_insert(list_t *list, size_t index, void *item);
+void list_del(list_t *list, size_t index);
+void *list_pop(list_t *list);
+void *list_peek(list_t *list);
+void list_cat(list_t *list, list_t *source);
+// See qsort. Remember to use *_qsort functions as compare functions,
+// because they dereference the left and right arguments first!
+void list_qsort(list_t *list, int compare(const void *left, const void *right));
+// Return index for first item in list that returns 0 for given compare
+// function or -1 if none matches.
+int list_seq_find(list_t *list,
+		int compare(const void *item, const void *cmp_to),
+		const void *cmp_to);
+
+#endif