Implement all resolution change policies for desktop and tab capture.

content/browser/media/capture/capture_resolution_chooser.cc

+// Copyright 2015 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 "content/browser/media/capture/capture_resolution_chooser.h"
+
+#include "media/base/limits.h"
+#include "media/base/video_util.h"
+
+namespace content {
+
+namespace {
+
+// Compute the minimum frame size from the given |max_frame_size| and
+// |resolution_change_policy|.
+gfx::Size ComputeMinimumCaptureSize(
+    const gfx::Size& max_frame_size,
+    media::ResolutionChangePolicy resolution_change_policy) {
+  switch (resolution_change_policy) {
+    case media::RESOLUTION_POLICY_FIXED_RESOLUTION:
+      return max_frame_size;
+    case media::RESOLUTION_POLICY_FIXED_ASPECT_RATIO: {
+      // TODO(miu): This is a place-holder until "min constraints" are plumbed-
+      // in from the MediaStream framework.  http://crbug.com/473336
+      const int kMinLines = 180;
+      if (max_frame_size.height() <= kMinLines)
+        return max_frame_size;
+      const gfx::Size result(
+          kMinLines * max_frame_size.width() / max_frame_size.height(),
+          kMinLines);
+      if (result.width() <= 0 || result.width() > media::limits::kMaxDimension)
+        return max_frame_size;
+      return result;
+    }
+    case media::RESOLUTION_POLICY_ANY_WITHIN_LIMIT:
+      return gfx::Size(1, 1);
+    case media::RESOLUTION_POLICY_LAST:
+      break;
+  }
+  NOTREACHED();
+  return gfx::Size(1, 1);
+}
+
+// Returns |size|, unless it exceeds |max_size| or is under |min_size|.  When
+// the bounds are exceeded, computes and returns an alternate size of similar
+// aspect ratio that is within the bounds.
+gfx::Size ComputeBoundedCaptureSize(const gfx::Size& size,
+                                    const gfx::Size& min_size,
+                                    const gfx::Size& max_size) {
+  if (size.width() > max_size.width() || size.height() > max_size.height()) {
+    gfx::Size result = media::ScaleSizeToFitWithinTarget(size, max_size);
+    result.SetToMax(min_size);
+    return result;
+  } else if (size.width() < min_size.width() ||
+             size.height() < min_size.height()) {
+    gfx::Size result = media::ScaleSizeToEncompassTarget(size, min_size);
+    result.SetToMin(max_size);
+    return result;
+  } else {
+    return size;
+  }
+}
+
+}  // namespace
+
+CaptureResolutionChooser::CaptureResolutionChooser(
+    const gfx::Size& max_frame_size,
+    media::ResolutionChangePolicy resolution_change_policy)
+    : max_frame_size_(max_frame_size),
+      min_frame_size_(ComputeMinimumCaptureSize(max_frame_size,
+                                                resolution_change_policy)),
+      resolution_change_policy_(resolution_change_policy),
+      constrained_size_(max_frame_size) {
+  DCHECK_LT(0, max_frame_size_.width());
+  DCHECK_LT(0, max_frame_size_.height());
+  DCHECK_LE(min_frame_size_.width(), max_frame_size_.width());
+  DCHECK_LE(min_frame_size_.height(), max_frame_size_.height());
+
+  RecomputeCaptureSize();
+}
+
+CaptureResolutionChooser::~CaptureResolutionChooser() {}
+
+void CaptureResolutionChooser::SetSourceSize(const gfx::Size& source_size) {
+  if (source_size.IsEmpty())
+    return;
+
+  switch (resolution_change_policy_) {
+    case media::RESOLUTION_POLICY_FIXED_RESOLUTION:
+      // Source size changes do not affect the frame resolution.  Frame
+      // resolution is always fixed to |max_frame_size_|.
+      break;
+
+    case media::RESOLUTION_POLICY_FIXED_ASPECT_RATIO:
+      constrained_size_ = ComputeBoundedCaptureSize(
+          media::PadToMatchAspectRatio(source_size, max_frame_size_),
+          min_frame_size_,
+          max_frame_size_);
+      RecomputeCaptureSize();
+      break;
+
+    case media::RESOLUTION_POLICY_ANY_WITHIN_LIMIT:
+      constrained_size_ = ComputeBoundedCaptureSize(
+          source_size, min_frame_size_, max_frame_size_);
+      RecomputeCaptureSize();
+      break;
+
+    case media::RESOLUTION_POLICY_LAST:
+      NOTREACHED();
+  }
+}
+
+void CaptureResolutionChooser::RecomputeCaptureSize() {
+  // TODO(miu): An upcoming change will introduce the ability to find the best
+  // capture resolution, given the current capabilities of the system.
+  // http://crbug.com/156767
+  capture_size_ = constrained_size_;
+}
+
+}  // namespace content