chrome/browser/net/client_hints.cc

   1 // Copyright 2013 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 "chrome/browser/net/client_hints.h"
   6
   7 #include <locale>
   8
   9 #include "base/bind.h"
  10 #include "base/strings/stringprintf.h"
  11 #include "base/task_runner_util.h"
  12 #include "content/public/browser/browser_thread.h"
  13 #include "ui/gfx/screen.h"
  14
  15 namespace {
  16
  17 float FetchScreenInfoOnUIThread() {
  18   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
  19   // TODO(bengr): Consider multi-display scenarios.
  20   gfx::Display display = gfx::Screen::GetNativeScreen()->GetPrimaryDisplay();
  21   return display.device_scale_factor();
  22 }
  23
  24 }  // namespace
  25
  26 const char ClientHints::kDevicePixelRatioHeader[] = "CH-DPR";
  27
  28 ClientHints::ClientHints()
  29     : weak_ptr_factory_(this) {
  30 }
  31
  32 ClientHints::~ClientHints() {
  33 }
  34
  35 void ClientHints::Init() {
  36   // TODO(bengr): Observe the device pixel ratio in case it changes during
  37   // the Chrome session.
  38   RetrieveScreenInfo();
  39 }
  40
  41 bool ClientHints::RetrieveScreenInfo() {
  42   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
  43   return content::BrowserThread::PostTaskAndReplyWithResult(
  44       content::BrowserThread::UI,
  45       FROM_HERE,
  46       base::Bind(&FetchScreenInfoOnUIThread),
  47       base::Bind(
  48           &ClientHints::UpdateScreenInfo, weak_ptr_factory_.GetWeakPtr()));
  49 }
  50
  51 const std::string& ClientHints::GetDevicePixelRatioHeader() const {
  52   return screen_hints_;
  53 }
  54
  55 void ClientHints::UpdateScreenInfo(float device_pixel_ratio_value) {
  56   if (device_pixel_ratio_value <= 0.0)
  57     return;
  58   std::string device_pixel_ratio = base::StringPrintf("%.2f",
  59       device_pixel_ratio_value);
  60   // Make sure the Client Hints value doesn't change
  61   // according to the machine's locale
  62   std::locale locale;
  63   for (std::string::iterator it = device_pixel_ratio.begin();
  64        it != device_pixel_ratio.end(); ++it) {
  65     if (!std::isdigit(*it, locale))
  66       *it = '.';
  67   }
  68   screen_hints_ = device_pixel_ratio;
  69 }
  70