Improvements to Dart and DartTrap (#2554)

Removes all hard-coded coordinates and offsets in darttrap.cpp, now the darts will always spawn in the centre of the hitbox's height (width for up and down darts). This makes it much more intuitive to create custom sprites for DartTrap. The default sprite is adjusted for this in a way that won't affect existing levels.
It also makes it possible to change the sprite of the dispensed Dart from DartTrap's menu in the editor.
Darts and DartTraps now also support UP and DOWN directions, in addition to LEFT and RIGHT.
This PR also cleans up darttrap.cpp/hpp according to the guidelines, namely adding the m_ prefix to member variables.

data/images/creatures/dart/dart.sprite

@@ -2,11 +2,23 @@
   (action
     (name "flying-left")
     (hitbox 10 6 12 7)
-    (images "flying.png")
-    )
+    (images "flying-left.png")
+  )
   (action
     (name "flying-right")
     (hitbox 10 6 12 7)
     (mirror-action "flying-left")
-    )
   )
+  (action
+    (name "flying-down")
+    (hitbox 6 10 7 12)
+    (images "flying-down.png")
+  )
+  ;; This will never show up since the editor uses the flipped down texture
+  ;; But it prevents warnings for missing actions
+  (action
+    (name "editor-up")
+    (hitbox 6 10 7 12)
+    (images "flying-down.png")
+  )
+)

data/images/creatures/darttrap/darttrap.sprite

@@ -1,39 +1,73 @@
 (supertux-sprite
   (action
-    (hitbox 21 13 11 37)
+    (hitbox 21 13 11 54)
     (name "idle-left")
-	(loops 1)
-    (images "d3-.png"
-	  "d3-.png"
-	  "d3-.png"
-	  "d3-.png"
-	  "d4.png"
-	  "d-idle.png")
+    (loops 1)
+    (images "left-3.png"
+      "left-3.png"
+      "left-3.png"
+      "left-3.png"
+      "left-4.png"
+      "left-idle.png"
+    )
+  )
+  (action
+    (hitbox 13 21 54 11)
+    (name "idle-down")
+    (loops 1)
+    (images "down-3.png"
+      "down-3.png"
+      "down-3.png"
+      "down-3.png"
+      "down-4.png"
+      "down-idle.png"
+    )
+  )
+  ;; This will never show up since the editor uses the flipped down texture
+  ;; But it prevents warnings for missing actions
+  (action
+    (hitbox 13 21 54 11)
+    (name "editor-up")
+    (images "down-1.png")
   )
   (action
-    (hitbox 21 13 11 37)
+    (hitbox 21 13 11 54)
     (name "idle-right")
-	(loops 1)
+    (loops 1)
     (mirror-action "idle-left")
   )
   (action
-    (hitbox 21 13 11 37)
+    (hitbox 21 13 11 54)
     (name "loading-left")
-	(fps 10)
+    (fps 10)
+    (images 
+      "left-idle.png"
+      "left-1.png"
+      "left-2.png"
+      "left-3.png"
+      "left-3.png"
+      "left-3.png"
+      "left-3.png"
+    )
+  )
+  (action
+    (hitbox 13 21 54 11)
+    (name "loading-down")
+    (fps 10)
     (images 
-      "d-idle.png"
-      "d1.png"
-	  "d2.png"
-	  "d3-.png"
-	  "d3-.png"
-	  "d3-.png"
-	  "d3-.png"
+      "down-idle.png"
+      "down-1.png"
+      "down-2.png"
+      "down-3.png"
+      "down-3.png"
+      "down-3.png"
+      "down-3.png"
     )
   )
   (action
-    (hitbox 21 13 11 37)
+    (hitbox 21 13 11 54)
     (name "loading-right")
-	(fps 10)
+    (fps 10)
     (mirror-action "loading-left")
   )
 )

data/images/engine/editor/objects.stoi

@@ -155,7 +155,7 @@
     (icon "images/creatures/angrystone/charging-0.png"))
   (object
     (class "darttrap")
-    (icon "images/creatures/darttrap/d1.png"))
+    (icon "images/creatures/darttrap/left-1.png"))
   (object
     (class "dispenser")
     (icon "images/creatures/dispenser/cannon_left.png"))
@@ -192,7 +192,7 @@
     (icon "images/creatures/skydive/skydive1.png"))
   (object
     (class "dart")
-    (icon "images/creatures/dart/flying.png"))
+    (icon "images/creatures/dart/flying-left.png"))
  )
 
  (objectgroup

src/badguy/dart.cpp

@@ -39,13 +39,14 @@ Dart::Dart(const ReaderMapping& reader) :
   SoundManager::current()->preload("sounds/stomp.wav");
 }
 
-Dart::Dart(const Vector& pos, Direction d, const BadGuy* parent_ = nullptr) :
-  BadGuy(pos, d, "images/creatures/dart/dart.sprite"),
+Dart::Dart(const Vector& pos, Direction d, const BadGuy* parent_, const std::string& sprite, Flip flip) :
+  BadGuy(pos, d, sprite),
   parent(parent_),
   sound_source()
 {
   m_physic.enable_gravity(false);
   m_countMe = false;
+  m_flip = flip;
   SoundManager::current()->preload(DART_SOUND);
   SoundManager::current()->preload("sounds/darthit.wav");
   SoundManager::current()->preload("sounds/stomp.wav");
@@ -64,8 +65,10 @@ Dart::updatePointers(const GameObject* from_object, GameObject* to_object)
 void
 Dart::initialize()
 {
-  m_physic.set_velocity_x(m_dir == Direction::LEFT ? -::DART_SPEED : ::DART_SPEED);
-  set_action("flying", m_dir);
+  m_physic.set_velocity_x(m_dir == Direction::LEFT ? -::DART_SPEED : m_dir == Direction::RIGHT ? ::DART_SPEED : 0);
+  m_physic.set_velocity_y(m_dir == Direction::UP ? -::DART_SPEED : m_dir == Direction::DOWN ? ::DART_SPEED : 0);
+  set_action("flying", m_dir == Direction::UP ? Direction::DOWN : m_dir);
+  if (m_dir == Direction::UP) m_flip = VERTICAL_FLIP;
 }
 
 void
@@ -143,11 +146,29 @@ Dart::play_looping_sounds()
   }
 }
 
+void
+Dart::after_editor_set()
+{
+  BadGuy::after_editor_set();
+  if ((m_dir == Direction::UP && m_flip == NO_FLIP) || (m_dir == Direction::DOWN && m_flip == VERTICAL_FLIP))
+    FlipLevelTransformer::transform_flip(m_flip);
+}
+
 void
 Dart::on_flip(float height)
 {
   BadGuy::on_flip(height);
   FlipLevelTransformer::transform_flip(m_flip);
+  if (m_dir == Direction::UP)
+  {
+    m_dir = Direction::DOWN;
+    m_physic.set_velocity_y(::DART_SPEED);
+  }
+  else if (m_dir == Direction::DOWN)
+  {
+    m_dir = Direction::UP;
+    m_physic.set_velocity_y(-::DART_SPEED);
+  }
 }
 
 /* EOF */

src/badguy/dart.hpp

@@ -26,7 +26,7 @@ class Dart final : public BadGuy
 {
 public:
   Dart(const ReaderMapping& reader);
-  Dart(const Vector& pos, Direction d, const BadGuy* parent);
+  Dart(const Vector& pos, Direction d, const BadGuy* parent, const std::string& sprite = "images/creatures/dart/dart.sprite", Flip flip = NO_FLIP);
 
   virtual void initialize() override;
   virtual void activate() override;
@@ -51,6 +51,7 @@ class Dart final : public BadGuy
   virtual void stop_looping_sounds() override;
   virtual void play_looping_sounds() override;
 
+  virtual void after_editor_set() override;
   virtual void on_flip(float height) override;
 
 protected: