Fix oneshot tap bug (#478)

overload() and timeout() rely on being able to store and execute descriptors
without tying them to specific key states. To achieve idempotence, oneshot()
currently neutralizes the upstroke of the activating key if the layer in
question is already active. This can yield an activation asymmetry in the rare
event that the oneshot descriptor is not associated with a physical key and is
activated while the associated layer is already active.

To fix this, we activate the layer for each oneshot depression and keep track
of the oneshot activation depth.

TODO

@@ -5,3 +5,4 @@ cleanup manpage
 improved mouse support (integrate moused?)
 multi-user support (remove keyd group)
 split up the man page + add FAQ
+add descriptor state + isolate descriptor logic

src/keyboard.c

@@ -400,9 +400,9 @@ static void clear_oneshot(struct keyboard *kbd)
 	size_t i = 0;
 
 	for (i = 0; i < kbd->config.nr_layers; i++)
-		if (kbd->layer_state[i].oneshot) {
-			kbd->layer_state[i].oneshot = 0;
+		while (kbd->layer_state[i].oneshot_depth) {
 			deactivate_layer(kbd, i);
+			kbd->layer_state[i].oneshot_depth--;
 		}
 
 	kbd->oneshot_latch = 0;
@@ -614,17 +614,12 @@ static long process_descriptor(struct keyboard *kbd, uint8_t code,
 		idx = d->args[0].idx;
 
 		if (pressed) {
-			if (kbd->layer_state[idx].active) {
-				/* Neutralize the upstroke. */
-				cache_set(kbd, code, NULL);
-			} else {
-				activate_layer(kbd, code, idx);
-				update_mods(kbd, dl, 0);
-				kbd->oneshot_latch = 1;
-			}
+			activate_layer(kbd, code, idx);
+			update_mods(kbd, dl, 0);
+			kbd->oneshot_latch = 1;
 		} else {
 			if (kbd->oneshot_latch) {
-				kbd->layer_state[idx].oneshot = 1;
+				kbd->layer_state[idx].oneshot_depth++;
 				if (kbd->config.oneshot_timeout) {
 					kbd->oneshot_timeout = time + kbd->config.oneshot_timeout;
 					schedule_timeout(kbd, kbd->oneshot_timeout);
@@ -717,12 +712,12 @@ static long process_descriptor(struct keyboard *kbd, uint8_t code,
 				activate_layer(kbd, 0, idx);
 				kbd->layer_state[idx].toggled = 1;
 				update_mods(kbd, -1, 0);
-			} else if (kbd->layer_state[dl].oneshot) {
+			} else if (kbd->layer_state[dl].oneshot_depth) {
 				deactivate_layer(kbd, dl);
-				kbd->layer_state[dl].oneshot = 0;
+				kbd->layer_state[dl].oneshot_depth--;
 
 				activate_layer(kbd, 0, idx);
-				kbd->layer_state[idx].oneshot = 1;
+				kbd->layer_state[idx].oneshot_depth++;
 				update_mods(kbd, -1, 0);
 			} else {
 				for (i = 0; i < CACHE_SIZE; i++) {

src/keyboard.h

@@ -117,7 +117,7 @@ struct keyboard {
 
 		uint8_t active;
 		uint8_t toggled;
-		uint8_t oneshot;
+		uint8_t oneshot_depth;
 	} layer_state[MAX_LAYERS];
 
 	uint8_t keystate[256];

t/overload-oneshot.t

@@ -0,0 +1,13 @@
+control down
+7 down
+7 up
+control up
+x down
+x up
+
+control down
+meta down
+meta up
+x down
+x up
+control up