before anim rewrite

src/engine/engine_init.c

@@ -3,6 +3,8 @@
 #include "internal/engine_internal.h"
 #include "internal/util/error.h"
 
+#include <stdlib.h>
+
 bool
 engine_sdl_init_state(
 	engine_sdl_state_t **state,

src/engine/render/anim.c

@@ -2,6 +2,7 @@
 
 void
 anim_rect_pos(
+    framebuffer_e framebuffer,
     uint32_t x0,
     uint32_t y0,
     uint32_t x1,
@@ -10,13 +11,28 @@ anim_rect_pos(
     uint32_t h,
     uint32_t color
 ) {
-    // TODO: I THINK I NEED LAYERED BUFFERS
+    // there's nowhere to move
+    if (x0 == x1 && y0 == y1) {
+        return;
+    }
 
-    // one step is one pixel
-    uint32_t stepsx = x1 - x0;
-    uint32_t stepsy = y1 - y0;
+    uint32_t dirx = (x1 - x0 > 0) ? 1 : -1;
+    uint32_t diry = (y1 - y0 > 0) ? 1 : -1;
+
+    if (x0 == x1) {
+        dirx = 0;
+    }
+    
+    if (y0 == y1) {
+        diry = 0;
+    }
 
     /**
-     * 1. get the row / column in the direction of the movement
+     * 1. shift the rectangle by one pixel in the direction of movement
+     * 2. remove the trailing row / column left  
      */
+
+    if (true) {
+
+    }
 }