refactor get_mouse_deltas() to accept buffer and read_count instead of index

examples/usb_host_descriptors_two_boot_mice.py

@@ -78,24 +78,22 @@ for device in usb.core.find(find_all=True):
 BUTTONS = ["left", "right", "middle"]
 
 mouse_bufs = []
-mouse_read_counts = [0, 0]
+
 for mouse_tg in mouse_tgs:
     # Buffer to hold data read from the mouse
     # Boot mice have 4 byte reports
-    mouse_bufs.append(array.array("b", [0] * 4))
+    mouse_bufs.append(array.array("b", [0] * 8))
 
 
-def get_mouse_deltas(mouse_index):
-    if mouse_read_counts[mouse_index] == 4:
-        delta_x = mouse_bufs[mouse_index][1]
-        delta_y = mouse_bufs[mouse_index][2]
-    elif mouse_read_counts[mouse_index] == 8:
-        delta_x = mouse_bufs[mouse_index][2]
-        delta_y = mouse_bufs[mouse_index][4]
+def get_mouse_deltas(buffer, read_count):
+    if read_count == 4:
+        delta_x = buffer[1]
+        delta_y = buffer[2]
+    elif read_count == 8:
+        delta_x = buffer[2]
+        delta_y = buffer[4]
     else:
-        raise ValueError(
-            f"Unsupported mouse packet size: {mouse_packet_sizes[mouse_index]}, must be 4 or 8"
-        )
+        raise ValueError(f"Unsupported mouse packet size: {read_count}, must be 4 or 8")
     return delta_x, delta_y
 
 
@@ -105,10 +103,9 @@ while True:
             count = mouse.read(
                 mouse_endpoint_addresses[mouse_index], mouse_bufs[mouse_index], timeout=10
             )
-            mouse_read_counts[mouse_index] = count
         except usb.core.USBTimeoutError:
             continue
-        mouse_deltas = get_mouse_deltas(mouse_index)
+        mouse_deltas = get_mouse_deltas(mouse_bufs[mouse_index], count)
         mouse_tgs[mouse_index].x = max(
             0, min(display.width - 1, mouse_tgs[mouse_index].x + mouse_deltas[0])
         )