Desktop chrome tab capture-chooseDesktopMedia()

content/public/browser/web_contents_media_capture_id.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[mark a. foltz, 2016/01/04 20:11:41]

s/2012/2016/

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/public/browser/web_contents_media_capture_id.h"
+
+#include <tuple>
+
+#include "base/basictypes.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+
+namespace content {
+const char kEnableFlag[] = "?throttling=auto";
+
+bool WebContentsMediaCaptureId::operator<(
+    const WebContentsMediaCaptureId& other) const {
+  return std::tie(render_process_id, main_render_frame_id,
+                  enable_auto_throttling) <
+         std::tie(other.render_process_id, other.main_render_frame_id,
+                  other.enable_auto_throttling);
+}
+
+bool WebContentsMediaCaptureId::operator==(
+    const WebContentsMediaCaptureId& other) const {
+  return std::tie(render_process_id, main_render_frame_id,
+                  enable_auto_throttling) ==
+         std::tie(other.render_process_id, other.main_render_frame_id,
+                  other.enable_auto_throttling);
+}
+
+bool WebContentsMediaCaptureId::is_null() const {
+  return (render_process_id < 0) || (main_render_frame_id < 0);

[mark a. foltz, 2016/01/04 20:11:41]

What about kInvalidId?

+}
+
+std::string WebContentsMediaCaptureId::ToString() const {
+  std::string s = kWebContentsCaptureScheme;
+  s.append("://");
+  s.append(base::Int64ToString(render_process_id));
+  s.append(":");
+  s.append(base::Int64ToString(main_render_frame_id));
+
+  if (enable_auto_throttling)

[mark a. foltz, 2016/01/04 20:11:41]

This doesn't have anything to do with the target of capture, it's a parameter
that probably belongs in the video constraints object.

+    s.append(kEnableFlag);
+
+  return s;
+}
+
+WebContentsMediaCaptureId WebContentsMediaCaptureId::Parse(
+    const std::string& str) {
+  int render_process_id;
+  int main_render_frame_id;
+  if (!ExtractTabCaptureTarget(str, &render_process_id, &main_render_frame_id))
+    return WebContentsMediaCaptureId();
+
+  return WebContentsMediaCaptureId(render_process_id, main_render_frame_id,
+                                   IsAutoThrottlingOptionSet(str));
+}
+
+bool WebContentsMediaCaptureId::IsWebContentsDeviceId(
+    const std::string& device_id) {
+  int ignored;
+  return ExtractTabCaptureTarget(device_id, &ignored, &ignored);
+}
+
+bool WebContentsMediaCaptureId::ExtractTabCaptureTarget(

[mark a. foltz, 2016/01/04 20:11:41]

How is a client supposed to come up with the (render_frame_id,render_host_id) to
construct this magic URL?  Why can't you take a tab_id like the other extensions
APIs in chrome.tabs?

+    const std::string& device_id_param,
+    int* render_process_id,
+    int* main_render_frame_id) {
+  const std::string device_scheme =
+      std::string(kWebContentsCaptureScheme) + "://";
+  if (!base::StartsWith(device_id_param, device_scheme,
+                        base::CompareCase::SENSITIVE))
+    return false;
+
+  const std::string device_id =
+      device_id_param.substr(device_scheme.size() - 1);
+
+  const size_t sep_pos = device_id.find(':');
+  if (sep_pos == std::string::npos)
+    return false;
+
+  const base::StringPiece component1(device_id.data(), sep_pos);
+  size_t end_pos = device_id.find('?');
+  if (end_pos == std::string::npos)
+    end_pos = device_id.length();
+  const base::StringPiece component2(device_id.data() + sep_pos + 1,
+                                     end_pos - sep_pos - 1);
+
+  return (base::StringToInt(component1, render_process_id) &&
+          base::StringToInt(component2, main_render_frame_id));
+}
+
+bool WebContentsMediaCaptureId::IsAutoThrottlingOptionSet(
+    const std::string& device_id) {
+  if (!IsWebContentsDeviceId(device_id))
+    return false;
+
+  // Find the option part of the string and just do a naive string compare since
+  // there are no other options in the |device_id| to account for (at the time
+  // of this writing).
+  const size_t option_pos = device_id.find('?');
+  if (option_pos == std::string::npos)
+    return false;
+  const base::StringPiece component(device_id.data() + option_pos,
+                                    device_id.length() - option_pos);
+  return component.compare(kEnableFlag) == 0;
+}
+
+}  // namespace content