Add touch events to the protocol, the stub layer, and to the client plugin.

remoting/client/plugin/touch_input_scaler.cc

Index: remoting/client/plugin/touch_input_scaler.cc
diff --git a/remoting/client/plugin/touch_input_scaler.cc b/remoting/client/plugin/touch_input_scaler.cc
new file mode 100644
index 0000000000000000000000000000000000000000..11396ab931cce35003e79f87962b8b0d3abeb0c3
--- /dev/null
+++ b/remoting/client/plugin/touch_input_scaler.cc
@@ -0,0 +1,86 @@
+// Copyright 2015 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 "remoting/client/plugin/touch_input_scaler.h"
+
+#include "base/logging.h"
+#include "remoting/proto/event.pb.h"
+
+namespace remoting {
+
+using protocol::TouchEvent;
+using protocol::TouchEventPoint;
+
+namespace {
+
+// |value| is the number to be scaled. |output_max| is the output desktop's max
+// height or width. |input_max| is the input desktop's max height or width.
+float Scale(float value, int output_max, int input_max) {
+  DCHECK_GT(output_max, 0);
+  DCHECK_GT(input_max, 0);
+  value *= output_max;
+  value /= input_max;
+  return value;
+}
+
+// Same as Scale() but |value| will be scaled and clamped using |output_max| and
+// |input_max|.
+float ScaleAndClamp(float value, int output_max, int input_max) {
+  value = Scale(value, output_max, input_max);
+  return std::max(0.0f, std::min(static_cast<float>(output_max), value));
+}
+
+}  // namespace
+
+TouchInputScaler::TouchInputScaler(InputStub* input_stub)
+    : InputFilter(input_stub) {}
+
+TouchInputScaler::~TouchInputScaler() {}
+
+void TouchInputScaler::InjectTouchEvent(const TouchEvent& event) {
+  if (input_size_.is_empty() || output_size_.is_empty())
+    return;
+
+  // We scale based on the maximum input & output coordinates, rather than the
+  // input and output sizes, so that it's possible to reach the edge of the
+  // output when up-scaling.  We also take care to round up or down correctly,
+  // which is important when down-scaling.
+  TouchEvent out_event(event);
+  for (int i = 0; i < out_event.touch_points().size(); ++i) {
+    TouchEventPoint* point = out_event.mutable_touch_points(i);
+    if (point->has_x() || point->has_y()) {
+      DCHECK(point->has_x() && point->has_y());
+      point->set_x(
+          ScaleAndClamp(point->x(), output_size_.width(), input_size_.width()));
+      point->set_y(ScaleAndClamp(point->y(), output_size_.height(),
+                                 input_size_.height()));
+    }
+
+    // Also scale the touch size. Without scaling, the size on the host will not
+    // be right.
+    // For example
+    // Suppose:
+    //  - No size scaling.
+    //  - Client is a HiDPI Chromebook device.
+    //  - Host is running on a HiDPI Windows device.
+    // With the configuration above, the client will send the logical touch
+    // size to the host, therefore it will be smaller on the host.
+    // This is because a HiDPI Chromebook device (e.g. Pixel) has 2 by 2
+    // physical pixel mapped to a logical pixel.
+    // With scaling, the size would be the same.
+    // TODO(rkuroiwa): Also clamp. Note that point->angle() affects the maximum
+    // size (crbug.com/461526).
+    if (point->has_radius_x() || point->has_radius_y()) {
+      DCHECK(point->has_radius_x() && point->has_radius_y());
+      point->set_radius_x(
+          Scale(point->radius_x(), output_size_.width(), input_size_.width()));
+      point->set_radius_y(Scale(point->radius_y(), output_size_.height(),
+                                input_size_.height()));
+    }
+  }
+
+  InputFilter::InjectTouchEvent(out_event);
+}
+
+}  // namespace remoting