remoting/client/touch_input_scaler.cc

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "remoting/client/touch_input_scaler.h"
   6
   7 #include "base/logging.h"
   8 #include "remoting/proto/event.pb.h"
   9
  10 namespace remoting {
  11
  12 using protocol::TouchEvent;
  13 using protocol::TouchEventPoint;
  14
  15 namespace {
  16
  17 // |value| is the number to be scaled. |output_max| is the output desktop's max
  18 // height or width. |input_max| is the input desktop's max height or width.
  19 float Scale(float value, int output_max, int input_max) {
  20   DCHECK_GT(output_max, 0);
  21   DCHECK_GT(input_max, 0);
  22   value *= output_max;
  23   value /= input_max;
  24   return value;
  25 }
  26
  27 // Same as Scale() but |value| will be scaled and clamped using |output_max| and
  28 // |input_max|.
  29 float ScaleAndClamp(float value, int output_max, int input_max) {
  30   value = Scale(value, output_max, input_max);
  31   return std::max(0.0f, std::min(static_cast<float>(output_max), value));
  32 }
  33
  34 }  // namespace
  35
  36 TouchInputScaler::TouchInputScaler(InputStub* input_stub)
  37     : InputFilter(input_stub) {}
  38
  39 TouchInputScaler::~TouchInputScaler() {}
  40
  41 void TouchInputScaler::InjectTouchEvent(const TouchEvent& event) {
  42   if (input_size_.is_empty() || output_size_.is_empty())
  43     return;
  44
  45   // We scale based on the maximum input & output coordinates, rather than the
  46   // input and output sizes, so that it's possible to reach the edge of the
  47   // output when up-scaling.  We also take care to round up or down correctly,
  48   // which is important when down-scaling.
  49   TouchEvent out_event(event);
  50   for (int i = 0; i < out_event.touch_points().size(); ++i) {
  51     TouchEventPoint* point = out_event.mutable_touch_points(i);
  52     if (point->has_x() || point->has_y()) {
  53       DCHECK(point->has_x() && point->has_y());
  54       point->set_x(
  55           ScaleAndClamp(point->x(), output_size_.width(), input_size_.width()));
  56       point->set_y(ScaleAndClamp(point->y(), output_size_.height(),
  57                                  input_size_.height()));
  58     }
  59
  60     // Also scale the touch size. Without scaling, the size on the host will not
  61     // be right.
  62     // For example
  63     // Suppose:
  64     //  - No size scaling.
  65     //  - Client is a HiDPI Chromebook device.
  66     //  - Host is running on a HiDPI Windows device.
  67     // With the configuration above, the client will send the logical touch
  68     // size to the host, therefore it will be smaller on the host.
  69     // This is because a HiDPI Chromebook device (e.g. Pixel) has 2 by 2
  70     // physical pixel mapped to a logical pixel.
  71     // With scaling, the size would be the same.
  72     // TODO(rkuroiwa): Also clamp. Note that point->angle() affects the maximum
  73     // size (crbug.com/461526).
  74     if (point->has_radius_x() || point->has_radius_y()) {
  75       DCHECK(point->has_radius_x() && point->has_radius_y());
  76       point->set_radius_x(
  77           Scale(point->radius_x(), output_size_.width(), input_size_.width()));
  78       point->set_radius_y(Scale(point->radius_y(), output_size_.height(),
  79                                 input_size_.height()));
  80     }
  81   }
  82
  83   InputFilter::InjectTouchEvent(out_event);
  84 }
  85
  86 }  // namespace remoting