Merge pull request #175 from keyboardio/h/layers/momentary-reactivation

When a momentary layer is held, reactivate the layer if it turns off

src/layers.cpp

@@ -12,27 +12,46 @@ static void handleKeymapKeyswitchEvent(Key keymapEntry, uint8_t keyState) {
   if (keymapEntry.keyCode >= MOMENTARY_OFFSET) {
     uint8_t target = keymapEntry.keyCode - MOMENTARY_OFFSET;
 
-    if (keyToggledOn(keyState)) {
+    switch (target) {
-      if (target == KEYMAP_NEXT) {
+    case KEYMAP_NEXT:
+      if (keyToggledOn(keyState))
         Layer.next();
-      } else if (target == KEYMAP_PREVIOUS) {
+      else if (keyToggledOff(keyState))
         Layer.previous();
-      } else {
+      break;
-        Layer.on(target);
+
-      }
+    case KEYMAP_PREVIOUS:
-    }
+      if (keyToggledOn(keyState))
-    if (keyToggledOff(keyState)) {
-      if (target == KEYMAP_NEXT) {
         Layer.previous();
-      } else if (target == KEYMAP_PREVIOUS) {
+      else if (keyToggledOff(keyState))
         Layer.next();
-      } else {
+      break;
+
+    default:
+      /* The default case is when we are switching to a layer by its number, and
+       * is a bit more complicated than switching there when the key toggles on,
+       * and away when it toggles off.
+       *
+       * We want to handle the case where we have more than one momentary layer
+       * key on our keymap that point to the same target layer, and we hold
+       * both, and release one. In this case, the layer should remain active,
+       * because the second momentary key is still held.
+       *
+       * To do this, we turn the layer back on if the switcher key is still
+       * held, not only when it toggles on. So when one of them is released,
+       * that does turn the layer off, but with the other still being held, the
+       * layer will toggle back on in the same cycle.
+       */
+      if (keyIsPressed(keyState)) {
+        if (!Layer.isOn(target))
+          Layer.on(target);
+      } else if (keyToggledOff(keyState)) {
         Layer.off(target);
       }
+      break;
     }
-
-    // switch keymap and stay there
   } else if (keyToggledOn(keyState)) {
+    // switch keymap and stay there
     if (Layer.isOn(keymapEntry.keyCode) && keymapEntry.keyCode)
       Layer.off(keymapEntry.keyCode);
     else