flow/stopwatch_sk.cc

// Copyright 2013 The Flutter 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 "flutter/flow/stopwatch_sk.h"
#include "include/core/SkCanvas.h"
#include "include/core/SkImageInfo.h"
#include "include/core/SkPaint.h"
#include "include/core/SkPath.h"
#include "include/core/SkSize.h"
#include "include/core/SkSurface.h"

namespace flutter {

static const size_t kMaxSamples = 120;
static const size_t kMaxFrameMarkers = 8;

void SkStopwatchVisualizer::InitVisualizeSurface(SkISize size) const {
  // Mark as dirty if the size has changed.
  if (visualize_cache_surface_) {
    if (size.width() != visualize_cache_surface_->width() ||
        size.height() != visualize_cache_surface_->height()) {
      cache_dirty_ = true;
    };
  }

  if (!cache_dirty_) {
    return;
  }
  cache_dirty_ = false;

  // TODO(garyq): Use a GPU surface instead of a CPU surface.
  visualize_cache_surface_ =
      SkSurfaces::Raster(SkImageInfo::MakeN32Premul(size));

  SkCanvas* cache_canvas = visualize_cache_surface_->getCanvas();

  // Establish the graph position.
  const SkScalar x = 0;
  const SkScalar y = 0;
  const SkScalar width = size.width();
  const SkScalar height = size.height();

  SkPaint paint;
  paint.setColor(0x99FFFFFF);
  cache_canvas->drawRect(SkRect::MakeXYWH(x, y, width, height), paint);

  // Scale the graph to show frame times up to those that are 3 times the frame
  // time.
  const double one_frame_ms = GetFrameBudget().count();
  const double max_interval = one_frame_ms * 3.0;
  const double max_unit_interval = UnitFrameInterval(max_interval);

  // Draw the old data to initially populate the graph.
  // Prepare a path for the data. We start at the height of the last point, so
  // it looks like we wrap around
  SkPath path;
  path.setIsVolatile(true);
  path.moveTo(x, height);
  path.lineTo(
      x, y + height * (1.0 - UnitHeight(stopwatch_.GetLap(0).ToMillisecondsF(),
                                        max_unit_interval)));
  double unit_x;
  double unit_next_x = 0.0;
  for (size_t i = 0; i < kMaxSamples; i += 1) {
    unit_x = unit_next_x;
    unit_next_x = (static_cast<double>(i + 1) / kMaxSamples);
    const double sample_y =
        y + height * (1.0 - UnitHeight(stopwatch_.GetLap(i).ToMillisecondsF(),
                                       max_unit_interval));
    path.lineTo(x + width * unit_x, sample_y);
    path.lineTo(x + width * unit_next_x, sample_y);
  }
  path.lineTo(
      width,
      y + height *
              (1.0 -
               UnitHeight(stopwatch_.GetLap(kMaxSamples - 1).ToMillisecondsF(),
                          max_unit_interval)));
  path.lineTo(width, height);
  path.close();

  // Draw the graph.
  paint.setColor(0xAA0000FF);
  cache_canvas->drawPath(path, paint);
}

void SkStopwatchVisualizer::Visualize(DlCanvas* canvas,
                                      const SkRect& rect) const {
  // Initialize visualize cache if it has not yet been initialized.
  InitVisualizeSurface(SkISize::Make(rect.width(), rect.height()));

  SkCanvas* cache_canvas = visualize_cache_surface_->getCanvas();
  SkPaint paint;

  // Establish the graph position.
  const SkScalar x = 0;
  const SkScalar y = 0;
  const SkScalar width = visualize_cache_surface_->width();
  const SkScalar height = visualize_cache_surface_->height();

  // Scale the graph to show frame times up to those that are 3 times the frame
  // time.
  const double one_frame_ms = GetFrameBudget().count();
  const double max_interval = one_frame_ms * 3.0;
  const double max_unit_interval = UnitFrameInterval(max_interval);

  const double sample_unit_width = (1.0 / kMaxSamples);

  // Draw vertical replacement bar to erase old/stale pixels.
  paint.setColor(0x99FFFFFF);
  paint.setStyle(SkPaint::Style::kFill_Style);
  paint.setBlendMode(SkBlendMode::kSrc);
  double sample_x =
      x + width * (static_cast<double>(prev_drawn_sample_index_) / kMaxSamples);
  const auto eraser_rect = SkRect::MakeLTRB(
      sample_x, y, sample_x + width * sample_unit_width, height);
  cache_canvas->drawRect(eraser_rect, paint);

  // Draws blue timing bar for new data.
  paint.setColor(0xAA0000FF);
  paint.setBlendMode(SkBlendMode::kSrcOver);
  const auto bar_rect = SkRect::MakeLTRB(
      sample_x,
      y + height *
              (1.0 -
               UnitHeight(stopwatch_
                              .GetLap(stopwatch_.GetCurrentSample() == 0
                                          ? kMaxSamples - 1
                                          : stopwatch_.GetCurrentSample() - 1)
                              .ToMillisecondsF(),
                          max_unit_interval)),
      sample_x + width * sample_unit_width, height);
  cache_canvas->drawRect(bar_rect, paint);

  // Draw horizontal frame markers.
  paint.setStrokeWidth(0);  // hairline
  paint.setStyle(SkPaint::Style::kStroke_Style);
  paint.setColor(0xCC000000);

  if (max_interval > one_frame_ms) {
    // Paint the horizontal markers
    size_t frame_marker_count =
        static_cast<size_t>(max_interval / one_frame_ms);

    // Limit the number of markers displayed. After a certain point, the graph
    // becomes crowded
    if (frame_marker_count > kMaxFrameMarkers) {
      frame_marker_count = 1;
    }

    for (size_t frame_index = 0; frame_index < frame_marker_count;
         frame_index++) {
      const double frame_height =
          height * (1.0 - (UnitFrameInterval((frame_index + 1) * one_frame_ms) /
                           max_unit_interval));
      cache_canvas->drawLine(x, y + frame_height, width, y + frame_height,
                             paint);
    }
  }

  // Paint the vertical marker for the current frame.
  // We paint it over the current frame, not after it, because when we
  // paint this we don't yet have all the times for the current frame.
  paint.setStyle(SkPaint::Style::kFill_Style);
  paint.setBlendMode(SkBlendMode::kSrcOver);
  if (UnitFrameInterval(stopwatch_.LastLap().ToMillisecondsF()) > 1.0) {
    // budget exceeded
    paint.setColor(SK_ColorRED);
  } else {
    // within budget
    paint.setColor(SK_ColorGREEN);
  }
  sample_x = x + width * (static_cast<double>(stopwatch_.GetCurrentSample()) /
                          kMaxSamples);
  const auto marker_rect = SkRect::MakeLTRB(
      sample_x, y, sample_x + width * sample_unit_width, height);
  cache_canvas->drawRect(marker_rect, paint);
  prev_drawn_sample_index_ = stopwatch_.GetCurrentSample();

  // Draw the cached surface onto the output canvas.
  auto image = DlImage::Make(visualize_cache_surface_->makeImageSnapshot());
  canvas->DrawImage(image, {rect.x(), rect.y()},
                    DlImageSampling::kNearestNeighbor);
}

}  // namespace flutter