Add lettermod

docs/keyd.scdoc

@@ -697,9 +697,9 @@ A key may optionally be bound to an _action_ which accepts zero or more argument
 	Identical to overloadt, but additionally resolves as a hold in the
 	event of an intervening key tap.
 
-*overloadi(<action 1>, <action 2>, <timeout>)*
-	Activate \<action 1\> if the last non-action (i.e symbol) key was struck less
-	than \<timeout\> milliseconds ago, otherwise activate \<action 2\>.
+*overloadi(<action 1>, <action 2>, <idle timeout>)*
+	Activate <action 1> if the last non-action (i.e symbol) key was struck less
+	than <timeout> milliseconds ago, otherwise activate <action 2>.
 
 	This can be used in combination with other overload timeouts and is particularly
 	useful for overloading letter keys (often called 'homerow mods').
@@ -707,17 +707,26 @@ A key may optionally be bound to an _action_ which accepts zero or more argument
 	For example:
 
 ```
-	a = overloadi(a, overloadt(control, a, 200), 150)
+	a = overloadi(a, overloadt2(control, a, 200), 150)
 ```
 
-	will produce _a_ if:
+	will produce _a_ if and only if:
 
 		- _a_ is struck within 150ms of another non-action key.
-		- _a_ is struck more than 150ms after a non-action key but held for less than 200ms.
+		- _a_ is struck more than 150ms after the last non-action key but held for less than 200ms
+		  and there are no intervening key taps.
 
 	This reduces the visual latency by immediately resolving the key as a letter when
-	typed midword but also facilitates its use as a modifier if it is held for long 
-	enough with no preceding symbol.
+	typed midword, but also facilitates its use as a layer trigger if it is held for a long 
+	enough period with no intervening symbols.
+
+	Since this is a common usecase, a macro called *lettermod* (defined below) has been
+	defined to facilitate such definitions.
+
+*lettermod(<layer>, <key>, <idle timeout>, <hold timeout>)*
+	An alias for:
+
+		*overloadi(<key>, overloadt2(<layer>, <key>, <hold timeout>), <idle timeout>)*
 
 *timeout(<action 1>, <timeout>, <action 2>)*
 	If the key is held in isolation for more than _<timeout> ms_, activate the second

src/config.c

@@ -399,7 +399,7 @@ static int config_add_layer(struct config *config, const char *s)
 /* Modifies the input string */
 static int parse_fn(char *s,
 		    char **name,
-		    char *args[MAX_DESCRIPTOR_ARGS],
+		    char *args[5],
 		    size_t *nargs)
 {
 	char *c, *arg;
@@ -453,7 +453,7 @@ exit:
 			return -1;
 
 		if (arg != c) {
-			assert(*nargs < MAX_DESCRIPTOR_ARGS);
+			assert(*nargs < 5);
 			args[(*nargs)++] = arg;
 		}
 
@@ -541,7 +541,7 @@ static int parse_descriptor(char *s,
 			    struct config *config)
 {
 	char *fn = NULL;
-	char *args[MAX_DESCRIPTOR_ARGS];
+	char *args[5];
 	size_t nargs = 0;
 	uint8_t code, mods;
 	int ret;
@@ -615,6 +615,24 @@ static int parse_descriptor(char *s,
 	} else if (!parse_fn(s, &fn, args, &nargs)) {
 		int i;
 
+		if (!strcmp(fn, "lettermod")) {
+			char buf[1024];
+
+			if (nargs != 4) {
+				err("%s requires 4 arguments", fn);
+				return -1;
+			}
+
+			snprintf(buf, sizeof buf,
+				"overloadi(%s, overloadt2(%s, %s, %s), %s)",
+				args[1], args[0], args[1], args[3], args[2]);
+
+			if (parse_fn(buf, &fn, args, &nargs)) {
+				err("failed to parse %s", buf);
+				return -1;
+			}
+		}
+
 		for (i = 0; i < ARRAY_SIZE(actions); i++) {
 			if (!strcmp(actions[i].name, fn)) {
 				int j;