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WIP: Discard wrong size layer tree instead of rendering it #21108

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WIP: Discard wrong size layer tree instead of rendering it #21108

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5ddcb61
Add optional DiscardCallback parameter to Rasterizer::Draw
knopp Sep 11, 2020
0b5d499
Do not rasterzize wrong size layer tree after viewport metrics change
knopp Sep 11, 2020
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9 changes: 7 additions & 2 deletions shell/common/rasterizer.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -156,7 +156,8 @@ void Rasterizer::DrawLastLayerTree() {
DrawToSurface(*last_layer_tree_);
}

void Rasterizer::Draw(fml::RefPtr<Pipeline<flutter::LayerTree>> pipeline) {
void Rasterizer::Draw(fml::RefPtr<Pipeline<flutter::LayerTree>> pipeline,
DiscardCallback discardCallback) {
TRACE_EVENT0("flutter", "GPURasterizer::Draw");
if (raster_thread_merger_ &&
!raster_thread_merger_->IsOnRasterizingThread()) {
Expand All @@ -170,7 +171,11 @@ void Rasterizer::Draw(fml::RefPtr<Pipeline<flutter::LayerTree>> pipeline) {
RasterStatus raster_status = RasterStatus::kFailed;
Pipeline<flutter::LayerTree>::Consumer consumer =
[&](std::unique_ptr<LayerTree> layer_tree) {
raster_status = DoDraw(std::move(layer_tree));
if (discardCallback && discardCallback(*layer_tree.get())) {
raster_status = RasterStatus::kSuccess;
} else {
raster_status = DoDraw(std::move(layer_tree));
}
};

PipelineConsumeResult consume_result = pipeline->Consume(consumer);
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7 changes: 6 additions & 1 deletion shell/common/rasterizer.h
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Expand Up @@ -204,6 +204,8 @@ class Rasterizer final : public SnapshotDelegate {
///
flutter::TextureRegistry* GetTextureRegistry();

using DiscardCallback = std::function<bool(flutter::LayerTree&)>;
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@iskakaushik iskakaushik Sep 14, 2020

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Consider calling this LayerTreeDiscardCallback.


//----------------------------------------------------------------------------
/// @brief Takes the next item from the layer tree pipeline and executes
/// the raster thread frame workload for that pipeline item to
Expand Down Expand Up @@ -232,8 +234,11 @@ class Rasterizer final : public SnapshotDelegate {
///
/// @param[in] pipeline The layer tree pipeline to take the next layer tree
/// to render from.
/// @param[in] discardCallback if specified and returns true, the layer tree
// is discarded instead of being rendered
///
void Draw(fml::RefPtr<Pipeline<flutter::LayerTree>> pipeline);
void Draw(fml::RefPtr<Pipeline<flutter::LayerTree>> pipeline,
DiscardCallback discardCallback = nullptr);
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@iskakaushik iskakaushik Sep 14, 2020

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Rather than passing nullptr as the default here, what do you think of having a static callback that resolved to false each time?


//----------------------------------------------------------------------------
/// @brief The type of the screenshot to obtain of the previously
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28 changes: 18 additions & 10 deletions shell/common/shell.cc
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Expand Up @@ -822,20 +822,19 @@ void Shell::OnPlatformViewSetViewportMetrics(const ViewportMetrics& metrics) {

// This is the formula Android uses.
// https://android.googlesource.com/platform/frameworks/base/+/master/libs/hwui/renderthread/CacheManager.cpp#41
size_t max_bytes = metrics.physical_width * metrics.physical_height * 12 * 4;
task_runners_.GetRasterTaskRunner()->PostTask(
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@iskakaushik iskakaushik Sep 14, 2020

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Why is setting the resource cache size moved to line 1036?

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@knopp knopp Sep 14, 2020

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That's a good point. I think it's a remnant from the very first version where shell was actually synchronizing viewport event with rasterization. I don't think it's necessary anymore. I'll look into it.

[rasterizer = rasterizer_->GetWeakPtr(), max_bytes] {
if (rasterizer) {
rasterizer->SetResourceCacheMaxBytes(max_bytes, false);
}
});
resource_cache_max_bytes_update_ =
metrics.physical_width * metrics.physical_height * 12 * 4;

task_runners_.GetUITaskRunner()->PostTask(
[engine = engine_->GetWeakPtr(), metrics]() {
if (engine) {
engine->SetViewportMetrics(metrics);
}
});

std::scoped_lock<std::mutex> lock(resize_mutex_);
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@iskakaushik iskakaushik Sep 14, 2020

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nit: consider creating a new scope for this

{
   lock;
   expeced_frame_size_ = ...;
}

When someone tries to add more functionality to this method, they will not hold the lock for longer than needed.

expected_frame_size_ =
SkISize::Make(metrics.physical_width, metrics.physical_height);
}

// |PlatformView::Delegate|
Expand Down Expand Up @@ -1025,13 +1024,22 @@ void Shell::OnAnimatorDraw(fml::RefPtr<Pipeline<flutter::LayerTree>> pipeline,
}
}

size_t max_bytes = resource_cache_max_bytes_update_;
resource_cache_max_bytes_update_ = 0;

task_runners_.GetRasterTaskRunner()->PostTask(
[&waiting_for_first_frame = waiting_for_first_frame_,
&waiting_for_first_frame_condition = waiting_for_first_frame_condition_,
rasterizer = rasterizer_->GetWeakPtr(),
pipeline = std::move(pipeline)]() {
rasterizer = rasterizer_->GetWeakPtr(), max_bytes,
pipeline = std::move(pipeline), this]() {
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@iskakaushik iskakaushik Sep 14, 2020

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I think initializing the discard callback outside this lambda could make it easier to read and could avoid capturing this here.

Rasterizer::DiscardCallback discard_callback =
      [&resize_mutex = resize_mutex_,
       &expected_frame_size = expected_frame_size_](flutter::LayerTree& tree) {
        std::scoped_lock<std::mutex> lock(resize_mutex);
        return tree.frame_size() != expected_frame_size;
      };

And then passing &discard_callback = discard_callback rather than this.

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@knopp knopp Sep 14, 2020

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The capture should be then discard_callback = std::move(discard_callback). I'm not sure why capturing resize_mutex_ and expected_frame_size_ individually though instead of just capturing this in discard_callback.

if (rasterizer) {
rasterizer->Draw(pipeline);
if (max_bytes != 0) {
rasterizer->SetResourceCacheMaxBytes(max_bytes, false);
}
rasterizer->Draw(pipeline, [this](flutter::LayerTree& tree) {
std::scoped_lock<std::mutex> lock(resize_mutex_);
return tree.frame_size() != expected_frame_size_;
});

if (waiting_for_first_frame.load()) {
waiting_for_first_frame.store(false);
Expand Down
4 changes: 4 additions & 0 deletions shell/common/shell.h
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Expand Up @@ -425,6 +425,10 @@ class Shell final : public PlatformView::Delegate,
// and read from the raster thread.
std::atomic<float> display_refresh_rate_ = 0.0f;

std::mutex resize_mutex_;
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@iskakaushik iskakaushik Sep 14, 2020

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Can you add comments explaining the newly added fields?

SkISize expected_frame_size_ = SkISize::MakeEmpty();
size_t resource_cache_max_bytes_update_ = 0;

// How many frames have been timed since last report.
size_t UnreportedFramesCount() const;

Expand Down