From 21dafd1b6da66c0ad2dbfdfd7c12d3d65441f195 Mon Sep 17 00:00:00 2001
From: En Yi <en.yi@tutanota.com>
Date: Fri, 16 Jun 2023 16:28:19 +0800
Subject: [PATCH] Add kinematic mode to movement

Changelog:
- Kinematic mode ignores accelerations, that's all
- Update moveable to use kinematic mode and set accel & velocity to zero
  when entering gridmove mode
---
 scenes/engine/EC/EC.h |  8 +++++++-
 scenes/game_systems.c | 27 ++++++++++++++++++---------
 2 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/scenes/engine/EC/EC.h b/scenes/engine/EC/EC.h
index 0e41feb..916eeec 100644
--- a/scenes/engine/EC/EC.h
+++ b/scenes/engine/EC/EC.h
@@ -26,6 +26,11 @@ typedef enum ComponentEnum {
     CMOVEABLE_T,
 } ComponentEnum_t;
 
+typedef enum MovementMode {
+    REGULAR_MOVEMENT = 0,
+    KINEMATIC_MOVEMENT,
+}MovementMode_t;
+
 typedef struct _CBBox_t {
     Vector2 size;
     Vector2 offset;
@@ -36,13 +41,14 @@ typedef struct _CBBox_t {
 
 typedef struct _CTransform_t {
     Vector2 prev_position;
+    Vector2 prev_velocity;
     Vector2 position;
     Vector2 velocity;
-    Vector2 prev_velocity;
     Vector2 accel;
     Vector2 fric_coeff;
     int8_t grav_delay;
     int8_t grav_timer;
+    MovementMode_t movement_mode;
 } CTransform_t;
 
 typedef struct _CMovementState_t {
diff --git a/scenes/game_systems.c b/scenes/game_systems.c
index fc75dec..993d71e 100644
--- a/scenes/game_systems.c
+++ b/scenes/game_systems.c
@@ -912,8 +912,6 @@ void moveable_update_system(Scene_t* scene)
 
         if (p_moveable->gridmove)
         {
-            memset(&p_ctransform->velocity, 0, sizeof(p_ctransform->velocity));
-            memset(&p_ctransform->accel, 0, sizeof(p_ctransform->velocity));
             float remaining_distance = p_moveable->target_pos.x - p_ctransform->position.x;
             if (fabs(remaining_distance) < 0.1)
             {
@@ -921,6 +919,7 @@ void moveable_update_system(Scene_t* scene)
                 p_ctransform->position = p_moveable->target_pos;
                 p_moveable->gridmove = false;
                 p_bbox->solid = true;
+                p_ctransform->movement_mode = REGULAR_MOVEMENT;
             }
             else if (remaining_distance > 0.1)
             {
@@ -929,6 +928,7 @@ void moveable_update_system(Scene_t* scene)
             else
             {
                 p_ctransform->position.x +=  (remaining_distance < -p_moveable->move_speed) ? -p_moveable->move_speed : remaining_distance;
+                memset(&p_ctransform->velocity, 0, sizeof(p_ctransform->velocity));
             }
         }
 
@@ -1035,6 +1035,9 @@ void moveable_update_system(Scene_t* scene)
                 p_bbox->solid = false;
                 p_moveable->prev_pos = p_ctransform->position;
                 p_moveable->target_pos = Vector2Scale((Vector2){tile_x,tile_y2}, TILE_SIZE); 
+                memset(&p_ctransform->velocity, 0, sizeof(p_ctransform->velocity));
+                memset(&p_ctransform->accel, 0, sizeof(p_ctransform->accel));
+                p_ctransform->movement_mode = KINEMATIC_MOVEMENT;
             }
 
         }
@@ -1119,6 +1122,9 @@ void player_pushing_system(Scene_t* scene)
                         p_other_moveable->gridmove = true;
                         p_other_moveable->prev_pos = p_other_ct->position;
                         p_other_moveable->target_pos = target_pos;
+                        memset(&p_ctransform->velocity, 0, sizeof(p_ctransform->velocity));
+                        memset(&p_ctransform->accel, 0, sizeof(p_ctransform->accel));
+                        p_other_ct->movement_mode = KINEMATIC_MOVEMENT;
                     }
                 }
             }
@@ -1137,11 +1143,15 @@ void movement_update_system(Scene_t* scene)
     sc_map_foreach(&scene->ent_manager.component_map[CTRANSFORM_COMP_T], ent_idx, p_ctransform)
     {
         p_ctransform->prev_velocity = p_ctransform->velocity;
-        p_ctransform->velocity =
-            Vector2Add(
-                p_ctransform->velocity,
-                Vector2Scale(p_ctransform->accel, delta_time)
-            );
+
+        if (p_ctransform->movement_mode == REGULAR_MOVEMENT)
+        {
+            p_ctransform->velocity =
+                Vector2Add(
+                    p_ctransform->velocity,
+                    Vector2Scale(p_ctransform->accel, delta_time)
+                );
+        }
 
         float mag = Vector2Length(p_ctransform->velocity);
         p_ctransform->velocity = Vector2Scale(
@@ -1159,8 +1169,7 @@ void movement_update_system(Scene_t* scene)
             p_ctransform->position,
             Vector2Scale(p_ctransform->velocity, delta_time)
         );
-        p_ctransform->accel.x = 0;
-        p_ctransform->accel.y = 0;
+        memset(&p_ctransform->accel, 0, sizeof(p_ctransform->accel));
 
         // Level boundary collision
         Entity_t* p_ent =  get_entity(&scene->ent_manager, ent_idx);