fixed pikvm/pikvm#159: workaround for windows 98 absolute mouse bug

hid/platformio.ini

@@ -24,6 +24,8 @@ build_flags =
 	-DHID_WITH_USB
 	-DHID_SET_USB_KBD
 	-DHID_SET_USB_MOUSE_ABS
+# ----- The USB ABS fix for Windows 98 (https://github.com/pikvm/pikvm/issues/159) -----
+#	-DHID_USB_ABS_WIN98_FIX
 # ----- PS2 keyboard only -----
 #	-DHID_WITH_PS2
 #	-DHID_SET_PS2_KBD

hid/src/usb/hid.h

@@ -161,7 +161,11 @@ class UsbMouseAbsolute {
 
 		void sendMove(int x, int y) {
 			CHECK_HID_EP;
+#ifdef HID_USB_ABS_WIN98_FIX
+			_mouse.moveTo(x << 1, y << 1);
+#else
 			_mouse.moveTo(x, y);
+#endif
 		}
 
 		void sendWheel(int delta_y) {

kvmd/plugins/hid/otg/__init__.py

@@ -72,7 +72,12 @@ class Plugin(BaseHid):  # pylint: disable=too-many-instance-attributes
         self.__output_to_mouse: Dict[str, MouseProcess] = {}
         self.__mouse_to_output: Dict[MouseProcess, str] = {}
         if mouse_alt["device_path"]:
-            self.__mouse_alt_proc = MouseProcess(absolute=(not mouse["absolute"]), **common, **mouse_alt)
+            self.__mouse_alt_proc = MouseProcess(
+                absolute=(not mouse["absolute"]),
+                absolute_win98_fix=mouse["absolute_win98_fix"],
+                **common,
+                **mouse_alt,
+            )
             self.__output_to_mouse = {
                 "usb": (self.__mouse_proc if mouse["absolute"] else self.__mouse_alt_proc),
                 "usb_rel": (self.__mouse_alt_proc if mouse["absolute"] else self.__mouse_proc),
@@ -94,6 +99,7 @@ class Plugin(BaseHid):  # pylint: disable=too-many-instance-attributes
                 "queue_timeout":    Option(0.1,  type=valid_float_f01),
                 "write_retries":    Option(150,  type=valid_int_f1),
                 "absolute":         Option(True, type=valid_bool),
+                "absolute_win98_fix": Option(False, type=valid_bool),
                 "horizontal_wheel": Option(True, type=valid_bool),
             },
             "mouse_alt": {
@@ -102,6 +108,7 @@ class Plugin(BaseHid):  # pylint: disable=too-many-instance-attributes
                 "queue_timeout":    Option(0.1,  type=valid_float_f01),
                 "write_retries":    Option(150,  type=valid_int_f1),
                 # No absolute option here, initialized by (not mouse.absolute)
+                # Also no absolute_win98_fix
                 "horizontal_wheel": Option(True, type=valid_bool),
             },
             "noop": Option(False, type=valid_bool),

kvmd/plugins/hid/otg/mouse.py

@@ -42,6 +42,7 @@ from .events import make_mouse_report
 class MouseProcess(BaseDeviceProcess):
     def __init__(self, **kwargs: Any) -> None:
         self.__absolute: bool = kwargs.pop("absolute")
+        self.__absolute_win98_fix: bool = kwargs.pop("absolute_win98_fix")
         self.__horizontal_wheel: bool = kwargs.pop("horizontal_wheel")
 
         super().__init__(
@@ -143,6 +144,12 @@ class MouseProcess(BaseDeviceProcess):
             assert relative_event is None
             move_x = self.__x
             move_y = self.__y
+            if self.__absolute_win98_fix:
+                # https://github.com/pikvm/pikvm/issues/159
+                # For some reason, the correct implementation of this fix
+                # is a shift to the left, and not to the right, as in VirtualBox
+                move_x <<= 1
+                move_y <<= 1
         else:
             assert self.__x == self.__y == 0
             if relative_event is not None: