refactor(player): Implement state-based input.

src/bettola.cpp

@@ -86,27 +86,31 @@ void Bettola::process_events(void) {
       _is_running = false;
     } else if(event.type == SDL_EVENT_KEY_DOWN) {
       switch(event.key.key) {
-        case SDLK_W: _player.move_up(); break;
-        case SDLK_S: _player.move_down(); break;
-        case SDLK_A: _player.move_left(); break;
-        case SDLK_D: _player.move_right(); break;
+        case SDLK_W: _input.up    = true; break;
+        case SDLK_S: _input.down  = true; break;
+        case SDLK_A: _input.left  = true; break;
+        case SDLK_D: _input.right = true; break;
       }
     } else if(event.type == SDL_EVENT_KEY_UP) {
       switch(event.key.key) {
-        case SDLK_W:
-        case SDLK_S:
-          _player.stop_vertical();
-          break;
-        case SDLK_A:
-        case SDLK_D:
-          _player.stop_horizontal();
-          break;
+        case SDLK_W: _input.up    = false; break;
+        case SDLK_S: _input.down  = false; break;
+        case SDLK_A: _input.left  = false; break;
+        case SDLK_D: _input.right = false; break;
       }
     }
   }
 }
 
 void Bettola::update(double dt) {
+  float dir_x = 0.0f;
+  float dir_y = 0.0f;
+  if(_input.up)     dir_y -= 1.0f;
+  if(_input.down)   dir_y += 1.0f;
+  if(_input.left)   dir_x -= 1.0f;
+  if(_input.right)  dir_x += 1.0f;
+  _player.set_velocity_direction(dir_x, dir_y);
+
   _player.update(dt);
 
   static char window_title[256];
@@ -127,8 +131,18 @@ void Bettola::render(void) {
   _shader.use();
 
   glm::mat4 model = glm::mat4(1.0f);
+#if 0
   model = glm::translate(model, glm::vec3(_player.get_x(), _player.get_y(), 0.0f));
   model = glm::scale(model, glm::vec3(_player.get_width(), _player.get_height(), 1.0f));
+#endif
+  /* to achieve Scale -> Rotate -> Translate,
+   * we need to apply operations in reverse!
+   */
+  glm::mat4 trans = glm::translate(glm::mat4(1.0f), glm::vec3(_player.get_x(),
+                                                              _player.get_y(),0.0f));
+  glm::mat4 scale = glm::scale(glm::mat4(1.0f), glm::vec3(_player.get_width(),
+                                                          _player.get_height(), 1.0f));
+  model = trans * scale;
 
   unsigned int model_loc = glGetUniformLocation(_shader.get_id(), "model");
   glUniformMatrix4fv(model_loc, 1, GL_FALSE, glm::value_ptr(model));

src/bettola.h

@@ -24,6 +24,13 @@ private:
   bool create_gl_context(void);
   void setup_quad(void);
 
+  struct InputState {
+    bool up     = false;
+    bool down   = false;
+    bool left   = false;
+    bool right  = false;
+  };
+
   bool _is_running;
 
   SDL_Window*   _window;
@@ -35,4 +42,5 @@ private:
 
   glm::mat4 _projection;
   Player _player;
+  InputState _input;
 };

src/game/player.cpp

@@ -1,4 +1,7 @@
 #include "player.h"
+#include <cstdio>
+#include <glm/glm.hpp>
+#include <glm/vec2.hpp>
 
 Player::Player(void) :
     _x(400.0f),
@@ -14,15 +17,13 @@ void Player::update(double dt) {
   _y += _vy * dt;
 }
 
-void Player::move_up(void)    { _vy = -_speed; }
-void Player::move_down(void)  { _vy =  _speed; }
-void Player::move_left(void)  { _vx = -_speed; }
-void Player::move_right(void) { _vx =  _speed; }
+void Player::set_velocity_direction(float dir_x, float dir_y) {
+  glm::vec2 direction = { dir_x, dir_y };
 
-void Player::stop_vertical(void) {
-  _vy = 0.0f;
-}
+  if(glm::length(direction) > 0.0f) {
+    direction = glm::normalize(direction);
+  }
 
-void Player::stop_horizontal(void) {
-  _vx = 0.0f;
+  _vx = direction.x * _speed;
+  _vy = direction.y * _speed;
 }

src/game/player.h

@@ -13,10 +13,12 @@ public:
   void stop_vertical(void);
   void stop_horizontal(void);
 
-  float get_x() const       { return _x; }
-  float get_y() const       { return _y; }
-  float get_width() const   { return _width; }
-  float get_height() const  { return _height; }
+  void set_velocity_direction(float dir_x, float dir_y);
+
+  float get_x()       const { return _x; }
+  float get_y()       const { return _y; }
+  float get_width()   const { return _width; }
+  float get_height()  const { return _height; }
 
 private:
   float _x;