criteria: Add. Learn for_window command.

A criteria is a string in the form of `[class="regex.*" title="str"]`.
It is stored in a struct with a list of *tokens* which is a
attribute/value pair (stored as a `crit_token` struct). Most tokens will
also have a precompiled regex stored that will be used during criteria
matching.

for_window command: When a new view is created its metadata is tested
against all stored criteria, and if a match is found the associated
command list is executed.

Unfortunately some metadata is not available in sway at the moment
(specifically `instance`, `window_role` and `urgent`). Any criteria
string that tries to match an unsupported attribute will fail.

(Note that while the criteria code can be used to parse any criteria
string it is currently only used by the `for_window` command.)

include/config.h

@@ -66,6 +66,7 @@ struct sway_config {
 	list_t *cmd_queue;
 	list_t *workspace_outputs;
 	list_t *output_configs;
+	list_t *criteria;
 	struct sway_mode *current_mode;
 	uint32_t floating_mod;
 	enum swayc_layouts default_orientation;

include/criteria.h

@@ -0,0 +1,36 @@
+#ifndef _SWAY_CRITERIA_H
+#define _SWAY_CRITERIA_H
+
+#include "container.h"
+#include "list.h"
+
+/**
+ * Maps criteria (as a list of criteria tokens) to a command list.
+ *
+ * A list of tokens together represent a single criteria string (e.g.
+ * '[class="abc" title="xyz"]' becomes two criteria tokens).
+ *
+ * for_window: Views matching all criteria will have the bound command list
+ * executed on them.
+ *
+ * Set via `for_window <criteria> <cmd list>`.
+ */
+struct criteria {
+	list_t *tokens; // struct crit_token, contains compiled regex.
+	char *crit_raw; // entire criteria string (for logging)
+
+	char *cmdlist;
+};
+
+int criteria_cmp(const void *item, const void *data);
+void free_criteria(struct criteria *crit);
+
+// Pouplate list with crit_tokens extracted from criteria string, returns error
+// string or NULL if successful.
+char *extract_crit_tokens(list_t *tokens, const char *criteria);
+
+// Returns list of criteria that match given container. These criteria have
+// been set with `for_window` commands and have an associated cmdlist.
+list_t *criteria_for(swayc_t *cont);
+
+#endif