device-manager-evdev: handle tablet axis motion before button and tip events

Some tablets have a noticable pointer jump on tip down/up, causing unintended
lines during drawing. Likewise, a button event may have an axis update that we
currently ignore. libinput provides tablet axis events only if no other state
changes, the client must instead get the current axis data from the tip/button
event. So let's do this, process the event axis data during tip/button as
well.

A libinput recording to reproduce is the 'dots.yml' in
https://gitlab.freedesktop.org/libinput/libinput/issues/128

Fixes #289

1 files changed, 57 insertions, 40 deletions

diff --git a/clutter/clutter/evdev/clutter-device-manager-evdev.c b/clutter/clutter/evdev/clutter-device-manager-evdev.c
index f2aeda696..04d966c54 100644
--- a/clutter/clutter/evdev/clutter-device-manager-evdev.c
+++ b/clutter/clutter/evdev/clutter-device-manager-evdev.c
@@ -1194,6 +1194,53 @@ notify_discrete_axis (ClutterSeatEvdev              *seat,
                                              scroll_source);
 }
 
+static void
+process_tablet_axis (ClutterDeviceManagerEvdev *manager_evdev,
+                     struct libinput_event     *event)
+{
+  struct libinput_device *libinput_device = libinput_event_get_device (event);
+  guint64 time;
+  double x, y, dx, dy, *axes;
+  gfloat stage_width, stage_height;
+  ClutterStage *stage;
+  ClutterInputDevice *device;
+  struct libinput_event_tablet_tool *tablet_event =
+    libinput_event_get_tablet_tool_event (event);
+  ClutterInputDeviceEvdev *evdev_device;
+
+  device = libinput_device_get_user_data (libinput_device);
+  evdev_device = CLUTTER_INPUT_DEVICE_EVDEV (device);
+
+  stage = _clutter_input_device_get_stage (device);
+  if (!stage)
+    return;
+
+  axes = translate_tablet_axes (tablet_event,
+                                evdev_device->last_tool);
+  if (!axes)
+    return;
+
+  stage_width = clutter_actor_get_width (CLUTTER_ACTOR (stage));
+  stage_height = clutter_actor_get_height (CLUTTER_ACTOR (stage));
+
+  time = libinput_event_tablet_tool_get_time_usec (tablet_event);
+
+  if (clutter_input_device_get_mapping_mode (device) == CLUTTER_INPUT_DEVICE_MAPPING_RELATIVE ||
+      clutter_input_device_tool_get_tool_type (evdev_device->last_tool) == CLUTTER_INPUT_DEVICE_TOOL_MOUSE ||
+      clutter_input_device_tool_get_tool_type (evdev_device->last_tool) == CLUTTER_INPUT_DEVICE_TOOL_LENS)
+    {
+      dx = libinput_event_tablet_tool_get_dx (tablet_event);
+      dy = libinput_event_tablet_tool_get_dy (tablet_event);
+      notify_relative_tool_motion (device, time, dx, dy, axes);
+    }
+  else
+    {
+      x = libinput_event_tablet_tool_get_x_transformed (tablet_event, stage_width);
+      y = libinput_event_tablet_tool_get_y_transformed (tablet_event, stage_height);
+      notify_absolute_motion (device, time, x, y, axes);
+    }
+}
+
 static gboolean
 process_device_event (ClutterDeviceManagerEvdev *manager_evdev,
                       struct libinput_event *event)
@@ -1578,46 +1625,7 @@ process_device_event (ClutterDeviceManagerEvdev *manager_evdev,
       }
     case LIBINPUT_EVENT_TABLET_TOOL_AXIS:
       {
-        guint64 time;
-        double x, y, dx, dy, *axes;
-        gfloat stage_width, stage_height;
-        ClutterStage *stage;
-        struct libinput_event_tablet_tool *tablet_event =
-          libinput_event_get_tablet_tool_event (event);
-        ClutterInputDeviceEvdev *evdev_device;
-
-        device = libinput_device_get_user_data (libinput_device);
-        evdev_device = CLUTTER_INPUT_DEVICE_EVDEV (device);
-
-        stage = _clutter_input_device_get_stage (device);
-        if (!stage)
-          break;
-
-        axes = translate_tablet_axes (tablet_event,
-                                      evdev_device->last_tool);
-        if (!axes)
-          break;
-
-        stage_width = clutter_actor_get_width (CLUTTER_ACTOR (stage));
-        stage_height = clutter_actor_get_height (CLUTTER_ACTOR (stage));
-
-        time = libinput_event_tablet_tool_get_time_usec (tablet_event);
-
-        if (clutter_input_device_get_mapping_mode (device) == CLUTTER_INPUT_DEVICE_MAPPING_RELATIVE ||
-            clutter_input_device_tool_get_tool_type (evdev_device->last_tool) == CLUTTER_INPUT_DEVICE_TOOL_MOUSE ||
-            clutter_input_device_tool_get_tool_type (evdev_device->last_tool) == CLUTTER_INPUT_DEVICE_TOOL_LENS)
-          {
-            dx = libinput_event_tablet_tool_get_dx (tablet_event);
-            dy = libinput_event_tablet_tool_get_dy (tablet_event);
-            notify_relative_tool_motion (device, time, dx, dy, axes);
-          }
-        else
-          {
-            x = libinput_event_tablet_tool_get_x_transformed (tablet_event, stage_width);
-            y = libinput_event_tablet_tool_get_y_transformed (tablet_event, stage_height);
-            notify_absolute_motion (device, time, x, y, axes);
-          }
-
+        process_tablet_axis (manager_evdev, event);
         break;
       }
     case LIBINPUT_EVENT_TABLET_TOOL_PROXIMITY:
@@ -1649,6 +1657,8 @@ process_device_event (ClutterDeviceManagerEvdev *manager_evdev,
           libinput_event_get_tablet_tool_event (event);
         guint tablet_button;
 
+        process_tablet_axis (manager_evdev, event);
+
         device = libinput_device_get_user_data (libinput_device);
         time_us = libinput_event_tablet_tool_get_time_usec (tablet_event);
         tablet_button = libinput_event_tablet_tool_get_button (tablet_event);
@@ -1673,8 +1683,15 @@ process_device_event (ClutterDeviceManagerEvdev *manager_evdev,
         button_state = libinput_event_tablet_tool_get_tip_state (tablet_event) ==
                        LIBINPUT_TABLET_TOOL_TIP_DOWN;
 
+        /* To avoid jumps on tip, notify axes before the tip down event
+           but after the tip up event */
+        if (button_state)
+          process_tablet_axis (manager_evdev, event);
+
         clutter_seat_evdev_notify_button (seat_from_device (device), device,
                                           time_us, BTN_TOUCH, button_state);
+        if (!button_state)
+          process_tablet_axis (manager_evdev, event);
         break;
       }
     case LIBINPUT_EVENT_TABLET_PAD_BUTTON: