From c9e4da2c6f6325c21c9f9462d124bf98956ecc98 Mon Sep 17 00:00:00 2001
From: Raheman Vaiya <r.vaiya@gmail.com>
Date: Thu, 11 May 2023 17:46:50 -0400
Subject: [PATCH] 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                 |  1 +
 src/keyboard.c       | 23 +++++++++--------------
 src/keyboard.h       |  2 +-
 t/overload-oneshot.t | 13 +++++++++++++
 4 files changed, 24 insertions(+), 15 deletions(-)
 create mode 100644 t/overload-oneshot.t

diff --git a/TODO b/TODO
index b00e681..066adbc 100644
--- a/TODO
+++ b/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
diff --git a/src/keyboard.c b/src/keyboard.c
index 1954b6b..2f39d8d 100644
--- a/src/keyboard.c
+++ b/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++) {
diff --git a/src/keyboard.h b/src/keyboard.h
index 81742a5..8bb8af3 100644
--- a/src/keyboard.h
+++ b/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];
diff --git a/t/overload-oneshot.t b/t/overload-oneshot.t
new file mode 100644
index 0000000..a1967ab
--- /dev/null
+++ b/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