Rework bcat Crkbd and Lily58 modifier keys (#9692)

* Re-enable mouse keys to fix Chrome OS media keys

I'm not sure if there's a bug in Chrome OS, QMK, or both, but
EXTRAKEY_ENABLE isn't sufficient for media keys to work on Chrome OS.
Instead, MOUSEKEY_ENABLE is also required.

* Remove unnecessary SPLIT_USB_DETECT for Lily58

I've since swapped my Lily58 back to Elite-C v2 controllers with working
VBUS detection.

* Move Crkbd Esc and Ctrl keys; add some shortcuts

* Move MC_ALTT to userspace for cross-board support

* Sync Lily58 keymap with Crkbd

* Fix typos

1 files changed, 38 insertions, 1 deletions

diff --git a/users/bcat/bcat.c b/users/bcat/bcat.c
index 2b250c10f1..397d565da0 100644
--- a/users/bcat/bcat.c
+++ b/users/bcat/bcat.c
@@ -1,6 +1,43 @@
-#include "quantum.h"
+#include "bcat.h"
 
 #if defined(RGBLIGHT_ENABLE)
 /* Adjust RGB static hue ranges for shorter gradients than default. */
 const uint8_t RGBLED_GRADIENT_RANGES[] PROGMEM = {255, 127, 63, 31, 15};
 #endif
+
+static int8_t alt_tab_layer = -1;
+
+__attribute__((weak)) bool process_record_keymap(uint16_t keycode, keyrecord_t *record) { return true; }
+
+bool process_record_user(uint16_t keycode, keyrecord_t *record) {
+    if (!process_record_keymap(keycode, record)) {
+        return false;
+    }
+    switch (keycode) {
+        /* Alt+Tab that holds Alt until current layer is released: */
+        case MC_ALTT:
+            if (record->event.pressed) {
+                if (alt_tab_layer < 0) {
+                    alt_tab_layer = layer_switch_get_layer(record->event.key);
+                    register_code(KC_LALT);
+                }
+                register_code(KC_TAB);
+            } else {
+                unregister_code(KC_TAB);
+            }
+            return false;
+        default:
+            return true;
+    }
+}
+
+__attribute__((weak)) layer_state_t layer_state_set_keymap(layer_state_t state) { return state; }
+
+layer_state_t layer_state_set_user(layer_state_t state) {
+    state = layer_state_set_keymap(state);
+    if (alt_tab_layer >= 0 && !layer_state_cmp(state, alt_tab_layer)) {
+        unregister_code(KC_LALT);
+        alt_tab_layer = -1;
+    }
+    return state;
+}