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

[Carlos Garnacho <carlosg src gnome org>]

commit 176117c5f7bea92f5abe48b96acb50046732275e
Author: Peter Hutterer <peter hutterer who-t net>
Date:   Thu Sep 6 14:44:04 2018 +1000

    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

 .../clutter/evdev/clutter-device-manager-evdev.c   | 97 +++++++++++++---------
 1 file 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: