Add a back button gesture in clickwheel mode

src/lua/include/lua_thread.hpp

@@ -30,6 +30,7 @@ class LuaThread {
   auto RunScript(const std::string& path) -> bool;
 
   auto bridge() -> Bridge& { return *bridge_; }
+  auto state() -> lua_State* { return state_; }
 
  private:
   LuaThread(std::unique_ptr<Allocator>&, std::unique_ptr<Bridge>&, lua_State*);

src/ui/encoder_input.cpp

@@ -264,6 +264,26 @@ auto EncoderInput::Read(lv_indev_data_t* data) -> void {
           break;
       }
 
+      // Only trigger the directional long-press gestures if they trigger at the
+      // same time as a trigger on the overall touchwheel. This means the
+      // gestures only trigger if it's your only interaction with the wheel this
+      // press; scrolling and then resting on a direction should not trigger
+      // them.
+      trigger = TriggerKey(Keys::kTouchWheel, KeyStyle::kLongPress, now_ms);
+      if (trigger == Trigger::kLongPress) {
+        trigger =
+            TriggerKey(Keys::kDirectionalLeft, KeyStyle::kLongPress, now_ms);
+        switch (trigger) {
+          case Trigger::kNone:
+            break;
+          case Trigger::kClick:
+            break;
+          case Trigger::kLongPress:
+            events::Ui().Dispatch(internal::BackPressed{});
+            break;
+        }
+      }
+
       break;
   }
 }

src/ui/include/ui_fsm.hpp

@@ -130,6 +130,7 @@ class Lua : public UiState {
   void react(const audio::PlaybackStarted&) override;
   void react(const audio::PlaybackUpdate&) override;
   void react(const audio::PlaybackFinished&) override;
+  void react(const internal::BackPressed&) override;
 
   using UiState::react;
 

src/ui/ui_fsm.cpp

@@ -245,7 +245,7 @@ auto Lua::PushLuaScreen(lua_State* s) -> int {
   return 0;
 }
 
-auto Lua::PopLuaScreen(lua_State* s) -> int {
+auto Lua::PopLuaScreen(lua_State *s) -> int {
   PopScreen();
   luavgl_set_root(s, sCurrentScreen->content());
   lv_group_set_default(sCurrentScreen->group());
@@ -301,6 +301,10 @@ void Lua::react(const audio::PlaybackFinished&) {
   playback_playing_->Update(false);
 }
 
+void Lua::react(const internal::BackPressed& ev) {
+  PopLuaScreen(sLua->state());
+}
+
 void Browse::entry() {}
 
 void Browse::react(const internal::ShowSettingsPage& ev) {