Implement a JavaScript API for document scanning

chrome/browser/extensions/api/document_scan/document_scan_api.cc

+// Copyright 2014 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 "chrome/browser/extensions/api/document_scan/document_scan_api.h"
+
+#include <algorithm>
+
+#if defined(OS_CHROMEOS)
+#include "base/task_runner_util.h"
+#include "base/threading/worker_pool.h"
+#include "chromeos/dbus/dbus_thread_manager.h"
+#include "chromeos/dbus/lorgnette_manager_client.h"
+#include "chromeos/dbus/pipe_reader.h"
+#endif  // OS_CHROMEOS
+#include "content/public/browser/browser_thread.h"
+#include "extensions/browser/extension_system.h"
+#if defined(OS_CHROMEOS)
+#include "third_party/cros_system_api/dbus/service_constants.h"
+#endif  // OS_CHROMEOS
+
+using content::BrowserThread;
+using std::string;
+using std::vector;
+
+namespace {
+
+const char kImageScanFailedError[] = "Image scan failed";
+const char kScannerImageMimeTypePng[] = "image/png";
+const char kScannerNotAvailable[] = "Scanner not available";
+const char kScanFunctionNotImplementedError[] = "Scan function not implemented";
+const char kUserGestureRequiredError[] =
+    "User gesture required to perform scan";
+const char kPngImageDataUrlPrefix[] = "data:image/png;base64,";
+}  // namespace
+
+namespace extensions {
+
+namespace api {
+
+#if defined(OS_CHROMEOS)

[mef, 2014/10/13 15:59:54]

Suggest: split into 3 files:

document_scan_interface_chromeos.cc
document_scan_interface_nonchromeos.cc
document_scan_function.cc

[Paul Stewart, 2014/10/14 19:28:31]

Done, except for consistency sake with the generated references I've retained
the document_scan_api.cc for the function.

+class DocumentScanInterfaceImpl : public DocumentScanInterface {
+ public:
+  DocumentScanInterfaceImpl() {}
+  virtual ~DocumentScanInterfaceImpl() {}
+
+  virtual void ListScanners(
+      const ListScannersResultsCallback& callback) OVERRIDE;
+  virtual void Scan(const string& scanner_name,
+                    ScanMode mode,
+                    int resolution_dpi,
+                    const ScanResultsCallback& callback) OVERRIDE;
+
+ private:
+  void OnScannerListReceived(
+      const ListScannersResultsCallback& callback,
+      bool succeeded,
+      const chromeos::LorgnetteManagerClient::ScannerTable &scanners);
+  void OnScanCompleted(const ScanResultsCallback &callback, bool succeeded);
+  void OnScanDataCompleted();
+  string GetImageURL(string image_data);
+
+  scoped_ptr<chromeos::PipeReaderForString> pipe_reader_;
+  string scanned_image_data_;
+
+  DISALLOW_COPY_AND_ASSIGN(DocumentScanInterfaceImpl);
+};
+
+void DocumentScanInterfaceImpl::ListScanners(
+    const ListScannersResultsCallback& callback) {
+  chromeos::DBusThreadManager::Get()->GetLorgnetteManagerClient()->
+       ListScanners(base::Bind(
+           &DocumentScanInterfaceImpl::OnScannerListReceived,
+           base::Unretained(this),
+           callback));
+}
+
+void DocumentScanInterfaceImpl::OnScannerListReceived(
+    const ListScannersResultsCallback& callback,
+    bool succeeded,
+    const chromeos::LorgnetteManagerClient::ScannerTable &scanners) {
+  vector<ScannerDescription> scanner_descriptions;
+  for (chromeos::LorgnetteManagerClient::ScannerTable::const_iterator iter =
+           scanners.begin();
+       iter != scanners.end();
+       ++iter) {
+    ScannerDescription description;
+    description.name = iter->first;
+    const chromeos::LorgnetteManagerClient::ScannerTableEntry &entry =
+        iter->second;
+    chromeos::LorgnetteManagerClient::ScannerTableEntry::const_iterator info_it;
+    info_it = entry.find(lorgnette::kScannerPropertyManufacturer);
+    if (info_it != entry.end()) {
+      description.manufacturer = info_it->second;
+    }
+    info_it = entry.find(lorgnette::kScannerPropertyModel);
+    if (info_it != entry.end()) {
+      description.model = info_it->second;
+    }
+    info_it = entry.find(lorgnette::kScannerPropertyType);
+    if (info_it != entry.end()) {
+      description.scanner_type = info_it->second;
+    }
+    description.image_mime_type = kScannerImageMimeTypePng;
+    scanner_descriptions.push_back(description);
+  }
+  callback.Run(scanner_descriptions, "");
+}
+
+void DocumentScanInterfaceImpl::Scan(const string& scanner_name,
+                                     ScanMode mode,
+                                     int resolution_dpi,
+                                     const ScanResultsCallback& callback) {
+  VLOG(1) << "Choosing scanner " << scanner_name;
+  chromeos::LorgnetteManagerClient::ScanProperties properties;
+  switch (mode) {
+    case kScanModeColor:
+      properties.mode = lorgnette::kScanPropertyModeColor;
+      break;
+
+    case kScanModeGray:
+      properties.mode = lorgnette::kScanPropertyModeGray;
+      break;
+
+    case kScanModeLineart:
+      properties.mode = lorgnette::kScanPropertyModeLineart;
+      break;
+
+    default:
+      // Leave the mode parameter empty, thereby using the default.
+      break;
+  }
+
+  if (resolution_dpi != 0) {
+    properties.resolution_dpi = resolution_dpi;
+  }
+
+  const bool kTasksAreSlow = true;
+  scoped_refptr<base::TaskRunner> task_runner =
+      base::WorkerPool::GetTaskRunner(kTasksAreSlow);
+
+  pipe_reader_.reset(new chromeos::PipeReaderForString(
+      task_runner,
+      base::Bind(&DocumentScanInterfaceImpl::OnScanDataCompleted,
+                 base::Unretained(this))));
+  base::File file = pipe_reader_->StartIO();
+  base::PlatformFile platform_file = file.TakePlatformFile();
+  VLOG(1) << "ScanImage platform_file is " << platform_file;
+  chromeos::DBusThreadManager::Get()->GetLorgnetteManagerClient()->
+       ScanImage(scanner_name, platform_file, properties,
+                 base::Bind(&DocumentScanInterfaceImpl::OnScanCompleted,
+                            base::Unretained(this),
+                            callback));
+}
+
+void DocumentScanInterfaceImpl::OnScanCompleted(
+    const ScanResultsCallback &callback, bool succeeded) {
+  VLOG(1) << "ScanImage returns " << succeeded;
+  if (pipe_reader_.get()) {
+    pipe_reader_->OnDataReady(-1);  // terminate data stream
+  }
+
+  string error_string;
+  if (!succeeded) {
+    error_string = kImageScanFailedError;
+  }
+
+  vector<string> scanned_image_data_array;
+  scanned_image_data_array.push_back(GetImageURL(scanned_image_data_));
+  callback.Run(
+      document_scan::Scan::Results::Create(
+          scanned_image_data_array, kScannerImageMimeTypePng), error_string);
+}
+
+string DocumentScanInterfaceImpl::GetImageURL(string image_data) {
+  string image_data_base64;
+  base::Base64Encode(image_data, &image_data_base64);
+  return string(kPngImageDataUrlPrefix) + image_data_base64;
+}
+
+void DocumentScanInterfaceImpl::OnScanDataCompleted() {
+  pipe_reader_->GetData(&scanned_image_data_);
+  pipe_reader_.reset();
+}
+
+#else  // OS_CHROMEOS
+class DocumentScanInterfaceImpl : public DocumentScanInterface {

[mef, 2014/10/13 15:59:54]

If this is not implemented and not intended for implementation outside of
ChromeOS, is it needed at all?

[Paul Stewart, 2014/10/14 19:28:31]

The intent is to make it possible to implement this outside of ChromeOS.
For example, if Google Cloud Devices implements their cloud-based document
scanning using this API (which would be convenient), they could take over
this stub.  The ChromeOS variant may need to merge the GCD results with
the ChromeOS-specific results.  Also, non-ChromeoOS implementations may
choose to expose local OS-specific devices in the future as well.

+ public:
+  DocumentScanInterfaceImpl() {}
+  virtual ~DocumentScanInterfaceImpl() {}
+
+  virtual void ListScanners(
+      const ListScannersResultsCallback& callback) OVERRIDE {
+    callback.Run(vector<ScannerDescription> (), "");
+  }
+  virtual void Scan(const string& scanner_name,
+                    ScanMode mode,
+                    int resolution_dpi,
+                    const ScanResultsCallback& callback) OVERRIDE {
+    vector<string> null_scan_results;
+    callback.Run(document_scan::Scan::Results::Create(null_scan_results, ""),
+                 kScanFunctionNotImplementedError);
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DocumentScanInterfaceImpl);
+};
+#endif  // OS_CHROMEOS
+
+DocumentScanScanFunction::DocumentScanScanFunction()
+    : document_scan_interface_(new DocumentScanInterfaceImpl()) {}
+
+DocumentScanScanFunction::~DocumentScanScanFunction() {}
+
+bool DocumentScanScanFunction::Prepare() {
+  set_work_thread_id(BrowserThread::FILE);
+  params_ = document_scan::Scan::Params::Create(*args_);
+  EXTENSION_FUNCTION_VALIDATE(params_.get());
+  return true;
+}
+
+void DocumentScanScanFunction::AsyncWorkStart() {
+  if (!user_gesture()) {
+    error_ = kUserGestureRequiredError;
+    AsyncWorkCompleted();
+    return;
+  }
+
+  // Add a reference, which is balanced in OnScannerListReceived to keep the
+  // object around and allow the callback to be invoked.
+  AddRef();
+
+  document_scan_interface_->ListScanners(
+      base::Bind(&DocumentScanScanFunction::OnScannerListReceived,
+                 base::Unretained(this)));
+}
+
+void DocumentScanScanFunction::OnScannerListReceived(
+    const vector<DocumentScanInterface::ScannerDescription>&
+        scanner_descriptions,
+    const string& error) {
+  vector<DocumentScanInterface::ScannerDescription>::const_iterator
+      scanner_i = scanner_descriptions.begin();
+  if (params_->options.accepted_mime_types) {
+    vector<string>& accepted_types =
+        *params_->options.accepted_mime_types.get();
+    for (; scanner_i != scanner_descriptions.end(); ++scanner_i) {
+      if (std::find(accepted_types.begin(), accepted_types.end(),
+                    scanner_i->image_mime_type) != accepted_types.end()) {
+        break;
+      }
+    }
+  }
+
+  if (scanner_i == scanner_descriptions.end()) {
+    vector<string> null_scan_results;
+    results_ = document_scan::Scan::Results::Create(null_scan_results, "");
+    error_ = kScannerNotAvailable;
+    AsyncWorkCompleted();
+
+    // Balance the AddRef in AsyncWorkStart().
+    Release();
+    return;
+  }
+
+  // TODO(pstew): Display a user interface for choosing a scanner.
+  // This is where the scan mode, DPI, etc, would be specified.
+
+  document_scan_interface_->Scan(
+      scanner_i->name,
+      DocumentScanInterface::kScanModeColor,
+      0,
+      base::Bind(&DocumentScanScanFunction::OnResultsReceived,
+                 base::Unretained(this)));
+}
+
+void DocumentScanScanFunction::OnResultsReceived(
+    scoped_ptr<base::ListValue> results, const string& error) {
+  // TODO(pstew): Display receied scan in the UI and confirm that this
+  // scan should be sent to the caller.  If this is a multi-page scan,
+  // provide a means for adding additional scanned images up to the
+  // requested limit.
+  results_ = results.Pass();
+  error_ = error;
+  AsyncWorkCompleted();
+
+  // Balance the AddRef in AsyncWorkStart().
+  Release();
+}
+
+bool DocumentScanScanFunction::Respond() {
+  return error_.empty();
+}
+
+}  // namespace api
+
+}  // namespace extensions