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 71
