Parse android layer annotations in debugger, play back layers

Bug: skia:9626
Change-Id: I3ae8fa83520690f9af534e9ab0b70834d7890fb0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/256100
Commit-Queue: Nathaniel Nifong <nifong@google.com>
Reviewed-by: Kevin Lubick <kjlubick@google.com>
diff --git a/tools/debugger/DebugLayerManager.cpp b/tools/debugger/DebugLayerManager.cpp
new file mode 100644
index 0000000..c903d7b
--- /dev/null
+++ b/tools/debugger/DebugLayerManager.cpp
@@ -0,0 +1,142 @@
+/*
+ * Copyright 2019 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "tools/debugger/DebugLayerManager.h"
+
+#include "include/core/SkImage.h"
+#include "include/core/SkImageInfo.h"
+#include "include/core/SkPicture.h"
+#include "include/core/SkSurface.h"
+#include "include/private/SkTHash.h"
+#include "tools/debugger/DebugCanvas.h"
+
+#include <memory>
+#include <vector>
+#include <tuple>
+
+void DebugLayerManager::setCommand(int nodeId, int frame, int command) {
+  auto* drawEvent = fDraws.find({frame, nodeId});
+  if (!drawEvent) {
+    SkDebugf("Could not set command playhead for event {%d, %d}, it is not tracked by"
+      "DebugLayerManager.\n", frame, nodeId);
+    return;
+  }
+  const int count = drawEvent->debugCanvas->getSize();
+  drawEvent->command = command < count ? command : count - 1;
+  // Invalidate stored images that depended on this combination of node and frame.
+  // actually this does all of the events for this nodeId, but close enough.
+  auto relevantFrames = listFramesForNode(nodeId);
+  for (const auto& frame : relevantFrames) {
+    fDraws[{frame, nodeId}].image = nullptr;
+  }
+}
+
+void DebugLayerManager::storeSkPicture(int nodeId, int frame, sk_sp<SkPicture> picture,
+    SkIRect dirty) {
+  const LayerKey k = {frame, nodeId};
+
+  // Make debug canvas using bounds from SkPicture. This will be equal to whatever width and
+  // height were passed into SkPictureRecorder::beginRecording(w, h) which is the layer bounds.
+  const auto& layerBounds = picture->cullRect().roundOut();
+  auto debugCanvas = std::make_unique<DebugCanvas>(layerBounds);
+  // Must be set or they end up undefined due to cosmic rays, bad luck, etc.
+  debugCanvas->setOverdrawViz(false);
+  debugCanvas->setDrawGpuOpBounds(false);
+  debugCanvas->setClipVizColor(SK_ColorTRANSPARENT);
+  // Setting this allows a layer to contain another layer. TODO(nifong): write a test for this.
+  debugCanvas->setLayerManagerAndFrame(this, frame);
+  // Only draw picture to the debug canvas once.
+  debugCanvas->drawPicture(picture);
+  int numCommands = debugCanvas->getSize();
+
+  DrawEvent event = {
+    frame == 0 || dirty==layerBounds,            // fullRedraw
+    nullptr,                                      // image
+    std::move(debugCanvas),                       // debugCanvas
+    numCommands-1,                                // command
+    {layerBounds.height(), layerBounds.width()},  // layerBounds
+  };
+
+  fDraws.set(k, std::move(event));
+  keys.push_back(k);
+}
+
+sk_sp<SkImage> DebugLayerManager::getLayerAsImage(const int nodeId, const int frame) {
+  // What is the last frame having an SkPicture for this layer? call it frame N
+  // have cached image of it? if so, return it.
+  // if not, draw it at frame N by the following method:
+  // The picture at frame N could have been a full redraw, or it could have been clipped to a
+  // dirty region. In order to know what the layer looked like on this frame, we must draw every
+  // picture starting with the last full redraw, up to the last one before the current frame, since
+  // any of those previous draws could be showing through.
+
+  // list of frames this node was updated on.
+  auto relevantFrames = listFramesForNode(nodeId);
+  // find largest one not greater than `frame`.
+  uint32_t i = relevantFrames.size()-1;
+  while (relevantFrames[i] > frame) { i--; }
+  const int frameN = relevantFrames[i];
+  // Fetch the draw event
+  auto& drawEvent = fDraws[{frameN, nodeId}];
+  // if an image of this is cached, return it.
+  if (drawEvent.image) {
+    return drawEvent.image;
+  }
+  // when it's not cached, we'll have to render it in an offscreen surface.
+  // start at the last full redraw. (pick up counting backwards from above)
+  while (i>0 && !(fDraws[{relevantFrames[i], nodeId}].fullRedraw)) { i--; }
+  // The correct layer bounds can be obtained from any drawEvent on this layer.
+  // the color type and alpha type are chosen here to match wasm-skp-debugger/cpu.js which was
+  // chosen to match the capabilities of HTML canvas, which this ultimately has to be drawn into.
+  // TODO(nifong): introduce a method of letting the user choose the backend for this.
+  auto surface = SkSurface::MakeRaster(SkImageInfo::Make(drawEvent.layerBounds,
+    kRGBA_8888_SkColorType, kUnpremul_SkAlphaType, nullptr));
+  // draw everything from the last full redraw up to the current frame.
+  // other frames drawn are partial, meaning they were clipped to not completely cover the layer.
+  // count back up with i
+  auto* canvas = surface->getCanvas();
+  for (; i<relevantFrames.size() && relevantFrames[i]<=frameN; i++) {
+    auto& evt = fDraws[{relevantFrames[i], nodeId}];
+    evt.debugCanvas->drawTo(canvas, evt.command);
+    canvas->flush();
+  }
+  drawEvent.image = surface->makeImageSnapshot();
+  return drawEvent.image;
+}
+
+std::vector<DebugLayerManager::DrawEventSummary> DebugLayerManager::summarizeEvents(int frame) const {
+    std::vector<DrawEventSummary> result;
+  for (const auto& node : listNodesForFrame(frame)) {
+    auto* evt = fDraws.find({frame, node});
+    if (!evt) { continue; }
+    result.push_back({
+      node, evt->fullRedraw, evt->debugCanvas->getSize(),
+      evt->layerBounds.width(), evt->layerBounds.height()
+    });
+  }
+  return result;
+}
+
+std::vector<int> DebugLayerManager::listNodesForFrame(int frame) const {
+  std::vector<int> result;
+  for (const auto& key : keys) {
+    if (key.frame == frame) {
+      result.push_back(key.nodeId);
+    }
+  }
+  return result;
+}
+
+std::vector<int> DebugLayerManager::listFramesForNode(int nodeId) const {
+  std::vector<int> result;
+  for (const auto& key : keys) {
+    if (key.nodeId == nodeId) {
+      result.push_back(key.frame);
+    }
+  }
+  return result;
+}