x11: Store last axes from device

And use these for the missing axes if the valuator mask is incomplete.
This used to work fine on tablets because the Wacom driver ensures all
valuators are sent, which is not true if using the evdev driver.

https://bugzilla.gnome.org/show_bug.cgi?id=703610

3 files changed, 42 insertions, 2 deletions

diff --git a/gdk/x11/gdkdevice-xi2.c b/gdk/x11/gdkdevice-xi2.c
index b3289c0e92..fad8671120 100644
--- a/gdk/x11/gdkdevice-xi2.c
+++ b/gdk/x11/gdkdevice-xi2.c
@@ -51,6 +51,7 @@ struct _GdkX11DeviceXI2
 
   gint device_id;
   GArray *scroll_valuators;
+  gdouble *last_axes;
 };
 
 struct _GdkX11DeviceXI2Class
@@ -157,6 +158,7 @@ gdk_x11_device_xi2_finalize (GObject *object)
   GdkX11DeviceXI2 *device = GDK_X11_DEVICE_XI2 (object);
 
   g_array_free (device->scroll_valuators, TRUE);
+  g_free (device->last_axes);
 
   G_OBJECT_CLASS (gdk_x11_device_xi2_parent_class)->finalize (object);
 }
@@ -891,3 +893,29 @@ _gdk_x11_device_xi2_get_id (GdkX11DeviceXI2 *device)
 
   return device->device_id;
 }
+
+gdouble
+gdk_x11_device_xi2_get_last_axis_value (GdkX11DeviceXI2 *device,
+                                        gint             n_axis)
+{
+  if (n_axis >= gdk_device_get_n_axes (GDK_DEVICE (device)))
+    return 0;
+
+  if (!device->last_axes)
+    return 0;
+
+  return device->last_axes[n_axis];
+}
+
+void
+gdk_x11_device_xi2_store_axes (GdkX11DeviceXI2 *device,
+                               gdouble         *axes,
+                               gint             n_axes)
+{
+  g_free (device->last_axes);
+
+  if (axes && n_axes)
+    device->last_axes = g_memdup (axes, sizeof (gdouble) * n_axes);
+  else
+    device->last_axes = NULL;
+}
diff --git a/gdk/x11/gdkdevicemanager-xi2.c b/gdk/x11/gdkdevicemanager-xi2.c
index 50c1a00711..a57ecaf885 100644
--- a/gdk/x11/gdkdevicemanager-xi2.c
+++ b/gdk/x11/gdkdevicemanager-xi2.c
@@ -837,6 +837,7 @@ handle_device_changed (GdkX11DeviceManagerXI2 *device_manager,
     {
       _gdk_device_reset_axes (device);
       _gdk_device_xi2_unset_scroll_valuators ((GdkX11DeviceXI2 *) device);
+      gdk_x11_device_xi2_store_axes (GDK_X11_DEVICE_XI2 (device), NULL, 0);
       translate_device_classes (display, device, ev->classes, ev->num_classes);
 
       g_signal_emit_by_name (G_OBJECT (device), "changed");
@@ -939,13 +940,16 @@ translate_axes (GdkDevice       *device,
   axes = g_new0 (gdouble, n_axes);
   vals = valuators->values;
 
-  for (i = 0; i < valuators->mask_len * 8; i++)
+  for (i = 0; i < MIN (valuators->mask_len * 8, n_axes); i++)
     {
       GdkAxisUse use;
       gdouble val;
 
       if (!XIMaskIsSet (valuators->mask, i))
-        continue;
+        {
+          axes[i] = gdk_x11_device_xi2_get_last_axis_value (GDK_X11_DEVICE_XI2 (device), i);
+          continue;
+        }
 
       use = gdk_device_get_axis_use (device, i);
       val = *vals++;
@@ -970,6 +974,8 @@ translate_axes (GdkDevice       *device,
         }
     }
 
+  gdk_x11_device_xi2_store_axes (GDK_X11_DEVICE_XI2 (device), axes, n_axes);
+
   return axes;
 }
 
diff --git a/gdk/x11/gdkprivate-x11.h b/gdk/x11/gdkprivate-x11.h
index d5f3e1d74f..c2afecf46d 100644
--- a/gdk/x11/gdkprivate-x11.h
+++ b/gdk/x11/gdkprivate-x11.h
@@ -247,6 +247,12 @@ gboolean  _gdk_x11_device_xi2_get_scroll_delta    (GdkX11DeviceXI2    *device,
                                                    gdouble            *delta_ret);
 void     _gdk_device_xi2_reset_scroll_valuators   (GdkX11DeviceXI2    *device);
 
+gdouble  gdk_x11_device_xi2_get_last_axis_value (GdkX11DeviceXI2 *device,
+                                                 gint             n_axis);
+
+void     gdk_x11_device_xi2_store_axes          (GdkX11DeviceXI2 *device,
+                                                 gdouble         *axes,
+                                                 gint             n_axes);
 #endif
 
 void     _gdk_x11_event_translate_keyboard_string (GdkEventKey *event);