reduce scroll sensitivity

firmware/include/config.h

 
 #define INVERT_SCROLL_X_AXIS false
 #define INVERT_SCROLL_Y_AXIS false
+#define SCROLL_REDUCE_SENSITIVITY 10
 #define MIN_SCROLL_SUPPRESS_CLICK 10
 
 #define DEBOUNCE_DELAY_MS 5

firmware/include/controls.h

     int16_t delta_x, delta_y;
     int16_t scroll_x, scroll_y;
     bool scroll_lock, fake_middle;
+    int16_t internal_scroll_x, internal_scroll_y;
 };
 
 void controls_init(void);

firmware/src/controls.c

         mouse.delta_y = motion.delta_y;
     }
 
+    mouse.scroll_x = 0;
+    mouse.scroll_y = 0;
+
     if (mouse.scroll_lock) {
-        mouse.scroll_x = mouse.delta_x;
-        mouse.scroll_y = mouse.delta_y;
+        scroll_sum += abs(mouse.delta_x);
+        scroll_sum += abs(mouse.delta_y);
+
+        mouse.internal_scroll_x += mouse.delta_x;
+        mouse.internal_scroll_y += mouse.delta_y;
+
         mouse.delta_x = 0;
         mouse.delta_y = 0;
 
-        scroll_sum += abs(mouse.scroll_x);
-        scroll_sum += abs(mouse.scroll_y);
+        while (mouse.internal_scroll_x > SCROLL_REDUCE_SENSITIVITY) {
+            mouse.scroll_x += 1;
+            mouse.internal_scroll_x -= SCROLL_REDUCE_SENSITIVITY;
+        }
+        while (mouse.internal_scroll_x < -SCROLL_REDUCE_SENSITIVITY) {
+            mouse.scroll_x -= 1;
+            mouse.internal_scroll_x += SCROLL_REDUCE_SENSITIVITY;
+        }
+
+        while (mouse.internal_scroll_y > SCROLL_REDUCE_SENSITIVITY) {
+            mouse.scroll_y += 1;
+            mouse.internal_scroll_y -= SCROLL_REDUCE_SENSITIVITY;
+        }
+        while (mouse.internal_scroll_y < -SCROLL_REDUCE_SENSITIVITY) {
+            mouse.scroll_y -= 1;
+            mouse.internal_scroll_y += SCROLL_REDUCE_SENSITIVITY;
+        }
     } else {
-        mouse.scroll_x = 0;
-        mouse.scroll_y = 0;
+        mouse.internal_scroll_x = 0;
+        mouse.internal_scroll_y = 0;
     }
 
     if (mouse.fake_middle) {