Show the now playing screen after being locked for a while

lua/main.lua

@@ -1,8 +1,13 @@
 local font = require("font")
 local vol = require("volume")
+local controls = require("controls")
+local time = require("time")
+
+local lock_time = time.ticks()
 
 -- Set up property bindings that are used across every screen.
 GLOBAL_BINDINGS = {
+  -- Show an alert with the current volume whenver the volume changes.
   vol.current_pct:bind(function(pct)
     require("alerts").show(function()
       local container = lvgl.Object(nil, {
@@ -32,6 +37,18 @@ GLOBAL_BINDINGS = {
       container:center()
     end)
   end),
+  -- When the device has been locked for a while, default to showing the now
+  -- playing screen after unlocking.
+  controls.lock_switch:bind(function(locked)
+    if locked then
+      lock_time = time.ticks()
+    elseif time.ticks() - lock_time > 8000 then
+      local queue = require("queue")
+      if queue.size:get() > 0 then
+        require("playing"):pushIfNotShown()
+      end
+    end
+  end),
 }
 
 local backstack = require("backstack")

src/ui/include/ui_fsm.hpp

@@ -129,6 +129,7 @@ class UiState : public tinyfsm::Fsm<UiState> {
 
   static lua::Property sControlsScheme;
   static lua::Property sScrollSensitivity;
+  static lua::Property sLockSwitch;
 
   static lua::Property sDatabaseUpdating;
 };

src/ui/ui_fsm.cpp

@@ -280,6 +280,8 @@ lua::Property UiState::sScrollSensitivity{
       return true;
     }};
 
+lua::Property UiState::sLockSwitch{false};
+
 lua::Property UiState::sDatabaseUpdating{false};
 
 auto UiState::InitBootSplash(drivers::IGpios& gpios) -> bool {
@@ -326,6 +328,7 @@ int UiState::PopScreen() {
 void UiState::react(const system_fsm::KeyLockChanged& ev) {
   sDisplay->SetDisplayOn(!ev.locking);
   sInput->lock(ev.locking);
+  sLockSwitch.Update(ev.locking);
 }
 
 void UiState::react(const internal::ControlSchemeChanged&) {
@@ -516,6 +519,7 @@ void Lua::entry() {
                                {
                                    {"scheme", &sControlsScheme},
                                    {"scroll_sensitivity", &sScrollSensitivity},
+                                   {"lock_switch", &sLockSwitch},
                                });
 
     registry.AddPropertyModule(