Layers: Fix the initial state of layer 0

When starting up, we correctly set the active layer counter to one, and the
active layer stack will therefore correctly contain layer 0 as an active layer.
However, we weren't setting the `layer_state_` bitmap up properly, and as such,
`Layer.isActive(0)` was returning false, despite the layer being active as far
as lookups were concerned.

To fix this, we explicitly flip the 0th bit on in the newly introduced
`Layer.setup()` method, where the initial keymap cache update was moved to, too.

Fixes #951.

Signed-off-by: Gergely Nagy <algernon@keyboard.io>

src/kaleidoscope/Runtime.cpp

@@ -42,11 +42,7 @@ Runtime_::setup(void) {
 
   device().setup();
 
-  // Update the keymap cache, so we start with a non-empty state.
-  Layer.updateActiveLayers();
-  for (auto key_addr : KeyAddr::all()) {
-    Layer.updateLiveCompositeKeymap(key_addr);
-  }
+  Layer.setup();
 }
 
 void

src/kaleidoscope/layers.cpp

@@ -46,6 +46,17 @@ Key Layer_::live_composite_keymap_[Runtime.device().numKeys()];
 uint8_t Layer_::active_layer_keymap_[Runtime.device().numKeys()];
 Layer_::GetKeyFunction Layer_::getKey = &Layer_::getKeyFromPROGMEM;
 
+void Layer_::setup() {
+  // Explicitly set layer 0's state to 1
+  bitSet(layer_state_, 0);
+
+  // Update the keymap cache, so we start with a non-empty state.
+  Layer.updateActiveLayers();
+  for (auto key_addr : KeyAddr::all()) {
+    Layer.updateLiveCompositeKeymap(key_addr);
+  }
+}
+
 void Layer_::handleKeymapKeyswitchEvent(Key keymapEntry, uint8_t keyState) {
   if (keymapEntry.getKeyCode() >= LAYER_MOVE_OFFSET) {
     if (keyToggledOn(keyState)) {

src/kaleidoscope/layers.h

@@ -51,6 +51,8 @@ class Layer_ {
  public:
   Layer_() {}
 
+  void setup();
+
   /* There are two lookup functions, because we have two caches, and different
    * parts of the firmware will want to use either this or that (or perhaps
    * both, in rare cases).