Add a PrinterDiscoverer fake object.

chromeos/printing/fake_printer_detector.cc

+// Copyright 2016 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 "chromeos/printing/fake_printer_detector.h"
+
+#include <algorithm>
+#include <iterator>
+#include <memory>
+
+#include "base/bind.h"
+#include "base/memory/ptr_util.h"
+#include "base/strings/stringprintf.h"
+#include "base/threading/sequenced_task_runner_handle.h"
+#include "base/time/time.h"
+#include "chromeos/printing/printer_detector.h"
+
+namespace chromeos {
+
+// static
+std::unique_ptr<PrinterDetector> PrinterDetector::Create() {
+  return base::MakeUnique<FakePrinterDetector>();
+}
+
+FakePrinterDetector::~FakePrinterDetector() {}
+
+bool FakePrinterDetector::StartDiscovery() {
+  discovery_running_ = true;
+  base::SequencedTaskRunnerHandle::Get()->PostNonNestableDelayedTask(
+      FROM_HERE, base::Bind(&FakePrinterDetector::EmitPrinters,
+                            weak_ptr_factory_.GetWeakPtr(), 0, 2),
+      base::TimeDelta::FromMilliseconds(2000));
+  return true;
+}
+
+bool FakePrinterDetector::StopDiscovery() {
+  discovery_running_ = false;
+  return true;
+}
+
+void FakePrinterDetector::SetObserver(PrinterDetector::Observer* observer) {
+  observer_ = observer;
+}
+
+FakePrinterDetector::FakePrinterDetector()
+    : discovery_running_(false), observer_(nullptr), weak_ptr_factory_(this) {
+  for (int i = 0; i < 12; i++) {
+    // printer doesn't have a ppd
+    printers_.emplace_back(base::StringPrintf("GUID%2d", i));
+    printers_[i].set_display_name(base::StringPrintf("PrinterName%2d", i));
+    printers_[i].set_description(
+        base::StringPrintf("Printer%2dDescription", i));
+    printers_[i].set_manufacturer("Chromium");
+    printers_[i].set_model(i % 3 == 0 ? "Inkjet" : "Laser Maker");
+    printers_[i].set_uri(
+        base::StringPrintf("lpr://192.168.1.%d:9100/bldg/printer", i));
+    printers_[i].set_uuid(
+        base::StringPrintf("UUID-%4d-%4d-%4d-UUID", i * 3, i * 2, i));
+  }
+}
+
+void FakePrinterDetector::EmitPrinters(size_t start, size_t end) {
+  if (!discovery_running_)
+    return;
+
+  size_t clipped_end = std::min(printers_.size(), end);
+  if (observer_) {
+    auto start_iter = printers_.begin();
+    std::advance(start_iter, start);
+    auto end_iter = printers_.begin();
+    std::advance(end_iter, end);
+    std::vector<Printer> subset(start_iter, end_iter);
+    observer_->OnPrintersFound(subset);
+  }
+
+  if (clipped_end < end) {

[xdai1, 2016/09/19 18:56:10]

should be if (clipped_end < printers_.size()) ?

[skau, 2016/09/20 01:56:47]

I've changed it to end < printers_.size() since that's more straightforward. 
Using the computed value makes it unnecessarily complicated.

[xdai1, 2016/09/20 04:16:50]

I think It is incorrect to use end here since |end| can be large than
printers_.size() but |clipped_end| is guaranteed no larger than
printers_.size(), which means we might lost the data between [clipped_end,
printers_.size()] if we use |end| here.

[skau, 2016/10/03 22:57:26]

Done.

+    base::SequencedTaskRunnerHandle::Get()->PostNonNestableDelayedTask(
+        FROM_HERE, base::Bind(&FakePrinterDetector::EmitPrinters,
+                              weak_ptr_factory_.GetWeakPtr(), end, end + end),

[xdai1, 2016/09/19 18:56:10]

I guess the last two parameters should be (clipped_end, clipped_end + 2) or
something like that?

[skau, 2016/09/20 01:56:47]

Depends if you'd rather get [0,1],[2,3],...[10,11],[12,12] (multiples of 2) or
[0,1],[2,3],[4,7],[8,12] (powers of 2).  The actual batch sizes could be fairly
random.

+        base::TimeDelta::FromMilliseconds(2000));
+  }
+}
+
+}  // namespace chromeos