cast: support cursor rendering for tab capture

content/browser/media/capture/cursor_renderer.cc

+// Copyright (c) 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/cursor_renderer.h"
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "ui/aura/client/screen_position_client.h"
+#include "ui/aura/env.h"
+#include "ui/aura/window.h"
+#include "ui/aura/window_tree_host.h"
+#include "ui/base/cursor/cursors_aura.h"
+#include "ui/compositor/dip_util.h"
+#include "ui/compositor/layer.h"
+
+namespace content {
+
+namespace {
+
+int clip_byte(int x) {
+  return std::max(0, std::min(x, 255));
+}
+
+int alpha_blend(int alpha, int src, int dst) {
+  return (src * alpha + dst * (255 - alpha)) / 255;
+}
+
+}  // namespace
+
+CursorRenderer::CursorRenderer(aura::Window* window, bool enable_mouse_events)
+    : window_(window), enable_mouse_events_(enable_mouse_events) {
+  if (enable_mouse_events_)
+    window_->AddPreTargetHandler(this);
+  Clear();
+}
+
+CursorRenderer::~CursorRenderer() {
+  if (enable_mouse_events_)
+    window_->RemovePreTargetHandler(this);
+}
+
+void CursorRenderer::Clear() {
+  last_cursor_ = ui::Cursor();
+  window_size_when_cursor_last_updated_ = gfx::Size();
+  scaled_cursor_bitmap_.reset();
+}
+
+bool CursorRenderer::Update(const gfx::Rect& region_in_frame) {
+  const gfx::Rect window_bounds = window_->GetBoundsInScreen();
+  gfx::Point cursor_position = aura::Env::GetInstance()->last_mouse_location();
+  if (!window_bounds.Contains(cursor_position)) {
+    // Return early if there is no need to draw the cursor.
+    Clear();
+    return false;
+  }
+

[miu, 2015/10/20 02:12:44]

Please include changes in: https://codereview.chromium.org/1413803002/

[Irfan, 2015/10/21 23:01:07]

Done.

+  gfx::NativeCursor cursor = window_->GetHost()->last_cursor();
+  gfx::Point cursor_hot_point;
+  if (last_cursor_ != cursor ||
+      window_size_when_cursor_last_updated_ != window_bounds.size()) {
+    SkBitmap cursor_bitmap;
+    if (ui::GetCursorBitmap(cursor, &cursor_bitmap, &cursor_hot_point)) {
+      const int scaled_width = cursor_bitmap.width() * region_in_frame.width() /
+                               window_bounds.width();
+      const int scaled_height = cursor_bitmap.height() *
+                                region_in_frame.height() /
+                                window_bounds.height();
+      if (scaled_width <= 0 || scaled_height <= 0) {
+        Clear();
+        return false;
+      }
+      scaled_cursor_bitmap_ = skia::ImageOperations::Resize(
+          cursor_bitmap, skia::ImageOperations::RESIZE_BEST, scaled_width,
+          scaled_height);
+      last_cursor_ = cursor;
+      window_size_when_cursor_last_updated_ = window_bounds.size();
+    } else {
+      // Clear cursor state if ui::GetCursorBitmap failed so that we do not
+      // render cursor on the captured frame.
+      Clear();
+    }
+  }
+
+  cursor_position.Offset(-window_bounds.x() - cursor_hot_point.x(),
+                         -window_bounds.y() - cursor_hot_point.y());
+  cursor_position_in_frame_ = gfx::Point(
+      region_in_frame.x() +
+          cursor_position.x() * region_in_frame.width() / window_bounds.width(),
+      region_in_frame.y() +
+          cursor_position.y() * region_in_frame.height() /
+              window_bounds.height());
+
+  if (cursor_displayed_) {
+    // Stop displaying cursor if there has been no mouse movement
+    base::TimeDelta now = base::TimeDelta::FromInternalValue(

[miu, 2015/10/20 02:12:44]

FromInternalValue() and ToInternalValue() are only supposed to be used for by
serializing implementations, since they defeat the compile-time checking of time
value math.  Instead, you should:

  base::TimeDelta now = base::TimeTicks::Now() - base::TimeTicks();

But, for robustness, it'd be even better to use the utility function:

  #include "ui/events/event_utils.h"
  ...
  base::TimeDelta now = ui::EventTimeForNow();

[Irfan, 2015/10/21 23:01:07]

Done.

+        base::TimeTicks::Now().ToInternalValue());
+    if ((now - last_mouse_movement_timestamp_) >
+        base::TimeDelta::FromSeconds(MAX_IDLE_TIME))
+      cursor_displayed_ = false;
+  }
+  return cursor_displayed_;
+}
+
+// Helper function to composite a cursor bitmap on a YUV420 video frame.
+void CursorRenderer::RenderOnVideoFrame(
+    const scoped_refptr<media::VideoFrame>& target) const {
+  if (scaled_cursor_bitmap_.isNull())
+    return;
+
+  DCHECK(target);
+
+  gfx::Rect rect = gfx::IntersectRects(
+      gfx::Rect(scaled_cursor_bitmap_.width(), scaled_cursor_bitmap_.height()) +
+          gfx::Vector2d(cursor_position_in_frame_.x(),
+                        cursor_position_in_frame_.y()),
+      target->visible_rect());
+
+  scaled_cursor_bitmap_.lockPixels();
+  for (int y = rect.y(); y < rect.bottom(); ++y) {
+    int cursor_y = y - cursor_position_in_frame_.y();
+    uint8* yplane = target->data(media::VideoFrame::kYPlane) +
+                    y * target->row_bytes(media::VideoFrame::kYPlane);
+    uint8* uplane = target->data(media::VideoFrame::kUPlane) +
+                    (y / 2) * target->row_bytes(media::VideoFrame::kUPlane);
+    uint8* vplane = target->data(media::VideoFrame::kVPlane) +
+                    (y / 2) * target->row_bytes(media::VideoFrame::kVPlane);
+    for (int x = rect.x(); x < rect.right(); ++x) {
+      int cursor_x = x - cursor_position_in_frame_.x();
+      SkColor color = scaled_cursor_bitmap_.getColor(cursor_x, cursor_y);
+      int alpha = SkColorGetA(color);
+      int color_r = SkColorGetR(color);
+      int color_g = SkColorGetG(color);
+      int color_b = SkColorGetB(color);
+      int color_y = clip_byte(
+          ((color_r * 66 + color_g * 129 + color_b * 25 + 128) >> 8) + 16);
+      yplane[x] = alpha_blend(alpha, color_y, yplane[x]);
+
+      // Only sample U and V at even coordinates.
+      if ((x % 2 == 0) && (y % 2 == 0)) {
+        int color_u = clip_byte(
+            ((color_r * -38 + color_g * -74 + color_b * 112 + 128) >> 8) + 128);
+        int color_v = clip_byte(
+            ((color_r * 112 + color_g * -94 + color_b * -18 + 128) >> 8) + 128);
+        uplane[x / 2] = alpha_blend(alpha, color_u, uplane[x / 2]);
+        vplane[x / 2] = alpha_blend(alpha, color_v, vplane[x / 2]);
+      }
+    }
+  }
+  scaled_cursor_bitmap_.unlockPixels();
+}
+
+void CursorRenderer::OnMouseEvent(ui::MouseEvent* event) {
+  switch (event->type()) {
+    case ui::ET_MOUSE_MOVED:
+      if (!cursor_displayed_) {
+        if ((event->x() - last_mouse_position_x_) > MIN_MOVEMENT ||
+            (event->y() - last_mouse_position_y_) > MIN_MOVEMENT)
+          cursor_displayed_ = true;
+      }
+      if (cursor_displayed_) {
+        last_mouse_movement_timestamp_ = event->time_stamp();
+        last_mouse_position_x_ = event->x();
+        last_mouse_position_y_ = event->y();
+      }
+      break;
+    default:
+      break;
+  }
+}
+
+}  // namespace content