Move direct use of VideoCapturer::VideoAdapter to VideoSinkWants.

webrtc/media/base/videobroadcaster.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/media/base/videobroadcaster.h"
 
+#include <limits>
+
 #include "webrtc/base/checks.h"
 
 namespace rtc {
 
 VideoBroadcaster::VideoBroadcaster() {
   thread_checker_.DetachFromThread();
 }
 
 void VideoBroadcaster::AddOrUpdateSink(
     VideoSinkInterface<cricket::VideoFrame>* sink,
     const VideoSinkWants& wants) {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   RTC_DCHECK(sink != nullptr);
 
   SinkPair* sink_pair = FindSinkPair(sink);
   if (!sink_pair) {
     sinks_.push_back(SinkPair(sink, wants));
   } else {
     sink_pair->wants = wants;
   }
-
-  // Rotation must be applied by the source if one sink wants it.
-  current_wants_.rotation_applied = false;
-  for (auto& sink_pair : sinks_) {
-    current_wants_.rotation_applied |= sink_pair.wants.rotation_applied;
-  }
+  UpdateWants();
 }
 
 void VideoBroadcaster::RemoveSink(
     VideoSinkInterface<cricket::VideoFrame>* sink) {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   RTC_DCHECK(sink != nullptr);
   RTC_DCHECK(FindSinkPair(sink));
 
   sinks_.erase(std::remove_if(sinks_.begin(), sinks_.end(),
                               [sink](const SinkPair& sink_pair) {
                                 return sink_pair.sink == sink;
                               }),
                sinks_.end());
+  UpdateWants();
 }
 
 bool VideoBroadcaster::frame_wanted() const {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   return !sinks_.empty();
 }
 
 VideoSinkWants VideoBroadcaster::wants() const {
   RTC_DCHECK(thread_checker_.CalledOnValidThread());
   return current_wants_;
@@ skipping 10 matching lines @@
     const VideoSinkInterface<cricket::VideoFrame>* sink) {
   auto sink_pair_it = std::find_if(
       sinks_.begin(), sinks_.end(),
       [sink](const SinkPair& sink_pair) { return sink_pair.sink == sink; });
   if (sink_pair_it != sinks_.end()) {
     return &*sink_pair_it;
   }
   return nullptr;
 }
 
+void VideoBroadcaster::UpdateWants() {
+  RTC_DCHECK(thread_checker_.CalledOnValidThread());
+  // Rotation must be applied by the source if one sink wants it.
+  current_wants_.rotation_applied = false;
+  int max_pixels = std::numeric_limits<int>::max();
+  int more_than_pixels = std::numeric_limits<int>::max();
+  for (auto& sink_pair : sinks_) {
+    current_wants_.rotation_applied |= sink_pair.wants.rotation_applied;
+    if (sink_pair.wants.max_pixel_count &&
+        max_pixels > *sink_pair.wants.max_pixel_count) {
+      max_pixels = *sink_pair.wants.max_pixel_count;
+    }
+
+    if (sink_pair.wants.max_pixel_count_step_up &&
+        more_than_pixels > *sink_pair.wants.max_pixel_count_step_up) {
+      more_than_pixels = *sink_pair.wants.max_pixel_count_step_up;
+    }
+  }
+
+  current_wants_.max_pixel_count_step_up =
+      (more_than_pixels < std::numeric_limits<int>::max() &&
+       max_pixels > more_than_pixels)
+          ? rtc::Optional<int>(more_than_pixels)
+          : rtc::Optional<int>();
+
+  current_wants_.max_pixel_count =
+      (max_pixels < std::numeric_limits<int>::max())
+          ? rtc::Optional<int>(max_pixels)
+          : rtc::Optional<int>();
+}
+

[pthatcher1, 2016/02/25 07:40:30]

I think this would be more readable:

VideoSinkWants wants;
for (auto& sink : sinks_) {
  // wants.rotation_applied == ANY(sink.wants.rotation_applied)
  if (sink.wants.rotation_applied) {
    wants.rotation_applied = true;
  }
  // wants.max_pixel_count == MIN(sink.wants.max_pixel_count)
  if (sink.wants.max_pixel_count && (!wants.max_pixel_count ||
(sink_wants.max_pixel_count < wants.max_pixel_count))) {
    wants.max_pixel_count = sink.wants.max_pixel_count;
  }
  // wants.max_pixel_count_step_up == MIN(sink.wants.max_pixel_count_step_up)
  if (sink.wants.max_pixel_count_step_up && (!wants.max_pixel_count_step_up ||
(sink_wants.max_pixel_count_step_up < wants.max_pixel_count_step_up))) {
    wants.max_pixel_count_step_up = sink.wants.max_pixel_count_step_up;
  }
}

current_wants_ = wants;

[nisse-webrtc, 2016/02/25 09:31:07]

I think there's one more thing done in Per's version (which maybe needs a
comment). If it turns out that MIN(max_pixel_step_up) >= MIN(max_pixel), then in
the merged wants, max_pixel_step_up is left unset.

The comparisons could also written as

  if (sink.wants.max_pixel_count.value_or(std::numeric_limits<int>::max()) 
     < max_pixels) {     
    max_pixels = *sink.wants.max_pixel_count;
  }

Which would be elegant if it weren't for the numeric_limits thing being so
lengthy. And as you can guess, I still find the rtc::Optional unnecessary, but I
won't insist if you really like that interface.

[perkj_webrtc, 2016/02/25 13:57:07]

Added that condition afterwards and went with pthatchers suggestion.

 }  // namespace rtc