Fix #3569: Fix Tux not turning around in 1-block gaps

When Tux is in a 1-block gap, his horizontal velocity becomes zero.
If the fancy idle timer was active, the draw() function would wait
for the timer to finish before updating the sprite's direction,
ignoring user input. This patch adds a check during the idle wait
state to force an action update if the direction changes,
resetting the idle stage to zero.

A unit test (PlayerAnimationTest) was also added to verify the
state machine logic for the idle animation turnaround

Closes #3569

Author: gvalves2005

src/object/player.cpp

@@ -2238,6 +2238,8 @@ Player::draw(DrawingContext& context)
       const bool is_not_idle = std::all_of(IDLE_STAGES.begin(), IDLE_STAGES.end(),
         [this](const std::string& stage) { return m_sprite->get_action().find("-" + stage + "-") == std::string::npos; });
 
+      std::string base_idle_action = sa_prefix + "-" + IDLE_STAGES[0] + sa_postfix;
+
       if (is_not_idle || (m_should_fancy_idle && !m_fancy_idle_active) || m_reset_action)
       {
         m_idle_stage = 0;
@@ -2270,13 +2272,19 @@ Player::draw(DrawingContext& context)
           else
             set_action(sa_prefix + ("-" + IDLE_STAGES[m_idle_stage]) + sa_postfix, 1);
         }
+        else if(m_sprite->get_action() != base_idle_action)
+        {
+          m_idle_stage = 0;
+          set_action(base_idle_action);
+          m_sprite->set_animation_loops(-1);
+        }
       }
       else
       {
-        if (m_idle_stage != 0 || m_sprite->get_action() != sa_prefix + ("-" + IDLE_STAGES[0]) + sa_postfix)
+        if (m_idle_stage != 0 || m_sprite->get_action() != base_idle_action)
         {
           m_idle_stage = 0;
-          set_action(sa_prefix + ("-" + IDLE_STAGES[0]) + sa_postfix);
+          set_action(base_idle_action);
           m_sprite->set_animation_loops(-1);
         }
         m_fancy_idle_active = false;