ash: Add basic prediction code to the laser pointer.

ash/laser/laser_pointer_controller_unittest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/laser/laser_pointer_controller.h"
 #include "ash/laser/laser_pointer_controller_test_api.h"
 #include "ash/laser/laser_pointer_view.h"
 #include "ash/shell.h"
 #include "ash/test/ash_test_base.h"
 #include "ui/events/test/event_generator.h"
@@ skipping 93 matching lines @@
   // Verify that the laser pointer does not get shown if points are not coming
   // from the stylus, even when enabled.
   GetEventGenerator().ExitPenPointerMode();
   controller_test_api_.SetEnabled(true);
   GetEventGenerator().PressTouch();
   GetEventGenerator().MoveTouch(gfx::Point(10, 10));
   GetEventGenerator().MoveTouch(gfx::Point(11, 11));
   EXPECT_FALSE(controller_test_api_.IsShowingLaserPointer());
   GetEventGenerator().ReleaseTouch();
 }
+
+// Test to ensure the class responsible for drawing the laser pointer handles
+// prediction as expected when it receives points from stylus movements.
+TEST_F(LaserPointerControllerTest, LaserPointerPrediction) {
+  LaserPointerControllerTestApi controller_test_api_(controller_.get());
+
+  controller_test_api_.SetEnabled(true);
+  // The laser pointer mode only works with stylus.
+  GetEventGenerator().EnterPenPointerMode();
+  GetEventGenerator().PressTouch();
+  EXPECT_TRUE(controller_test_api_.IsShowingLaserPointer());
+
+  EXPECT_EQ(1, controller_test_api_.laser_points().GetNumberOfPoints());
+  // Initial press event shouldn't generate any predicted points as there's no
+  // history to use for prediction.
+  EXPECT_EQ(0,
+            controller_test_api_.predicted_laser_points().GetNumberOfPoints());
+
+  // Verify dragging the stylus 3 times will add some predicted points.
+  GetEventGenerator().MoveTouch(gfx::Point(10, 10));
+  GetEventGenerator().MoveTouch(gfx::Point(20, 20));
+  GetEventGenerator().MoveTouch(gfx::Point(30, 30));
+  EXPECT_NE(0,
+            controller_test_api_.predicted_laser_points().GetNumberOfPoints());

[Daniel Erat, 2017/03/16 20:18:30]

i hope you add some tests that verify the actual points in a followup change.
:-)

[reveman, 2017/03/16 20:42:49]

Added to latest patch.

+
+  // Verify releasing the stylus removes predicted points.
+  GetEventGenerator().ReleaseTouch();
+  EXPECT_TRUE(controller_test_api_.IsShowingLaserPointer());
+  EXPECT_TRUE(controller_test_api_.IsFadingAway());
+  EXPECT_EQ(0,
+            controller_test_api_.predicted_laser_points().GetNumberOfPoints());
+}
+
 }  // namespace ash