[Impeller] opt into exp canvas. (#54913)

Switch back to new canvas implementation, which allows us to complete the display list/impeller interop arc of work. While we're at it, switch the subpass size rounding logic to round out if there is no image filter.

Fixes flutter/flutter#152366

Part of flutter/flutter#142054

Author: Jonah Williams

common/config.gni

@@ -37,7 +37,7 @@ declare_args() {
   slimpeller = false
 
   # Opt into new DL dispatcher that skips AIKS layer
-  experimental_canvas = false
+  experimental_canvas = true
 }
 
 # feature_defines_list ---------------------------------------------------------

impeller/aiks/canvas.h

@@ -37,6 +37,11 @@ struct CanvasStackEntry {
   size_t num_clips = 0u;
   Scalar distributed_opacity = 1.0f;
   Entity::RenderingMode rendering_mode = Entity::RenderingMode::kDirect;
+  // Whether all entities in the current save should be skipped.
+  bool skipping = false;
+  // Whether subpass coverage was rounded out to pixel coverage, or if false
+  // truncated.
+  bool did_round_out = false;
 };
 
 enum class PointStyle {

impeller/aiks/experimental_canvas.cc

@@ -3,7 +3,10 @@
 // found in the LICENSE file.
 
 #include "impeller/aiks/experimental_canvas.h"
+
 #include <limits>
+#include <optional>
+
 #include "fml/logging.h"
 #include "fml/trace_event.h"
 #include "impeller/aiks/canvas.h"
@@ -61,7 +64,6 @@ static void ApplyFramebufferBlend(Entity& entity) {
 static std::shared_ptr<Texture> FlipBackdrop(
     std::vector<LazyRenderingConfig>& render_passes,
     Point global_pass_position,
-    size_t current_clip_depth,
     EntityPassClipStack& clip_coverage_stack,
     ContentContext& renderer) {
   auto rendering_config = std::move(render_passes.back());
@@ -137,21 +139,16 @@ static std::shared_ptr<Texture> FlipBackdrop(
 
   // Restore any clips that were recorded before the backdrop filter was
   // applied.
-  clip_coverage_stack.ActivateClipReplay();
-
-  // If there are any pending clips to replay, render any that may affect
-  // the entity we're about to render.
-  while (const EntityPassClipStack::ReplayResult* next_replay_clip =
-             clip_coverage_stack.GetNextReplayResult(current_clip_depth)) {
-    auto& replay_entity = next_replay_clip->entity;
+  auto& replay_entities = clip_coverage_stack.GetReplayEntities();
+  for (const auto& replay : replay_entities) {
     SetClipScissor(
-        next_replay_clip->clip_coverage,
+        replay.clip_coverage,
         *render_passes.back().inline_pass_context->GetRenderPass(0).pass,
         global_pass_position);
-    if (!replay_entity.Render(
+    if (!replay.entity.Render(
             renderer,
             *render_passes.back().inline_pass_context->GetRenderPass(0).pass)) {
-      VALIDATION_LOG << "Failed to render entity for clip replay.";
+      VALIDATION_LOG << "Failed to render entity for clip restore.";
     }
   }
 
@@ -296,41 +293,43 @@ void ExperimentalCanvas::SetupRenderPass() {
   }
 }
 
+void ExperimentalCanvas::SkipUntilMatchingRestore(size_t total_content_depth) {
+  auto entry = CanvasStackEntry{};
+  entry.skipping = true;
+  entry.clip_depth = current_depth_ + total_content_depth;
+  transform_stack_.push_back(entry);
+}
+
 void ExperimentalCanvas::Save(uint32_t total_content_depth) {
+  if (IsSkipping()) {
+    return SkipUntilMatchingRestore(total_content_depth);
+  }
+
   auto entry = CanvasStackEntry{};
   entry.transform = transform_stack_.back().transform;
   entry.cull_rect = transform_stack_.back().cull_rect;
   entry.clip_depth = current_depth_ + total_content_depth;
   entry.distributed_opacity = transform_stack_.back().distributed_opacity;
-  FML_CHECK(entry.clip_depth <= transform_stack_.back().clip_depth)
+  FML_DCHECK(entry.clip_depth <= transform_stack_.back().clip_depth)
       << entry.clip_depth << " <=? " << transform_stack_.back().clip_depth
       << " after allocating " << total_content_depth;
   entry.clip_height = transform_stack_.back().clip_height;
   entry.rendering_mode = Entity::RenderingMode::kDirect;
-  transform_stack_.emplace_back(entry);
+  transform_stack_.push_back(entry);
 }
 
-void ExperimentalCanvas::SaveLayer(
-    const Paint& paint,
-    std::optional<Rect> bounds,
-    const std::shared_ptr<ImageFilter>& backdrop_filter,
-    ContentBoundsPromise bounds_promise,
-    uint32_t total_content_depth,
-    bool can_distribute_opacity) {
-  TRACE_EVENT0("flutter", "Canvas::saveLayer");
-
+std::optional<Rect> ExperimentalCanvas::ComputeCoverageLimit() const {
   if (!clip_coverage_stack_.HasCoverage()) {
     // The current clip is empty. This means the pass texture won't be
     // visible, so skip it.
-    Save(total_content_depth);
-    return;
+    return std::nullopt;
   }
 
   auto maybe_current_clip_coverage = clip_coverage_stack_.CurrentClipCoverage();
   if (!maybe_current_clip_coverage.has_value()) {
-    Save(total_content_depth);
-    return;
+    return std::nullopt;
   }
+
   auto current_clip_coverage = maybe_current_clip_coverage.value();
 
   // The maximum coverage of the subpass. Subpasses textures should never
@@ -343,8 +342,28 @@ void ExperimentalCanvas::SaveLayer(
           .Intersection(current_clip_coverage);
 
   if (!maybe_coverage_limit.has_value() || maybe_coverage_limit->IsEmpty()) {
-    Save(total_content_depth);
-    return;
+    return std::nullopt;
+  }
+
+  return maybe_coverage_limit->Intersection(
+      Rect::MakeSize(render_target_.GetRenderTargetSize()));
+}
+
+void ExperimentalCanvas::SaveLayer(
+    const Paint& paint,
+    std::optional<Rect> bounds,
+    const std::shared_ptr<ImageFilter>& backdrop_filter,
+    ContentBoundsPromise bounds_promise,
+    uint32_t total_content_depth,
+    bool can_distribute_opacity) {
+  TRACE_EVENT0("flutter", "Canvas::saveLayer");
+  if (IsSkipping()) {
+    return SkipUntilMatchingRestore(total_content_depth);
+  }
+
+  auto maybe_coverage_limit = ComputeCoverageLimit();
+  if (!maybe_coverage_limit.has_value()) {
+    return SkipUntilMatchingRestore(total_content_depth);
   }
   auto coverage_limit = maybe_coverage_limit.value();
 
@@ -356,10 +375,9 @@ void ExperimentalCanvas::SaveLayer(
     return;
   }
 
-  std::shared_ptr<FilterContents> filter_contents;
-  if (paint.image_filter) {
-    filter_contents = paint.image_filter->GetFilterContents();
-  }
+  std::shared_ptr<FilterContents> filter_contents = paint.WithImageFilter(
+      Rect(), transform_stack_.back().transform,
+      Entity::RenderingMode::kSubpassPrependSnapshotTransform);
 
   std::optional<Rect> maybe_subpass_coverage = ComputeSaveLayerCoverage(
       bounds.value_or(Rect::MakeMaximum()),
@@ -371,13 +389,32 @@ void ExperimentalCanvas::SaveLayer(
       /*flood_input_coverage=*/!!backdrop_filter         //
   );
 
-  if (!maybe_subpass_coverage.has_value() ||
-      maybe_subpass_coverage->IsEmpty()) {
-    Save(total_content_depth);
-    return;
+  if (!maybe_subpass_coverage.has_value()) {
+    return SkipUntilMatchingRestore(total_content_depth);
   }
+
   auto subpass_coverage = maybe_subpass_coverage.value();
 
+  // When an image filter is present, clamp to avoid flicking due to nearest
+  // sampled image. For other cases, round out to ensure than any geometry is
+  // not cut off.
+  //
+  // See also this bug: https://github.com/flutter/flutter/issues/144213
+  //
+  // TODO(jonahwilliams): this could still round out for filters that use decal
+  // sampling mode.
+  ISize subpass_size;
+  bool did_round_out = false;
+  if (paint.image_filter) {
+    subpass_size = ISize(subpass_coverage.GetSize());
+  } else {
+    did_round_out = true;
+    subpass_size = ISize(IRect::RoundOut(subpass_coverage).GetSize());
+  }
+  if (subpass_size.IsEmpty()) {
+    return SkipUntilMatchingRestore(total_content_depth);
+  }
+
   // Backdrop filter state, ignored if there is no BDF.
   std::shared_ptr<FilterContents> backdrop_filter_contents;
   Point local_position = {0, 0};
@@ -393,11 +430,10 @@ void ExperimentalCanvas::SaveLayer(
           return filter;
         };
 
-    auto input_texture = FlipBackdrop(render_passes_,                        //
-                                      GetGlobalPassPosition(),               //
-                                      std::numeric_limits<uint32_t>::max(),  //
-                                      clip_coverage_stack_,                  //
-                                      renderer_                              //
+    auto input_texture = FlipBackdrop(render_passes_,           //
+                                      GetGlobalPassPosition(),  //
+                                      clip_coverage_stack_,     //
+                                      renderer_                 //
     );
     if (!input_texture) {
       // Validation failures are logged in FlipBackdrop.
@@ -419,23 +455,24 @@ void ExperimentalCanvas::SaveLayer(
   paint_copy.color.alpha *= transform_stack_.back().distributed_opacity;
   transform_stack_.back().distributed_opacity = 1.0;
 
-  render_passes_.push_back(LazyRenderingConfig(
-      renderer_,                                             //
-      CreateRenderTarget(renderer_,                          //
-                         ISize(subpass_coverage.GetSize()),  //
-                         Color::BlackTransparent()           //
-                         )));
+  render_passes_.push_back(
+      LazyRenderingConfig(renderer_,                                    //
+                          CreateRenderTarget(renderer_,                 //
+                                             subpass_size,              //
+                                             Color::BlackTransparent()  //
+                                             )));
   save_layer_state_.push_back(SaveLayerState{paint_copy, subpass_coverage});
 
   CanvasStackEntry entry;
   entry.transform = transform_stack_.back().transform;
   entry.cull_rect = transform_stack_.back().cull_rect;
   entry.clip_depth = current_depth_ + total_content_depth;
-  FML_CHECK(entry.clip_depth <= transform_stack_.back().clip_depth)
+  FML_DCHECK(entry.clip_depth <= transform_stack_.back().clip_depth)
       << entry.clip_depth << " <=? " << transform_stack_.back().clip_depth
       << " after allocating " << total_content_depth;
   entry.clip_height = transform_stack_.back().clip_height;
   entry.rendering_mode = Entity::RenderingMode::kSubpassAppendSnapshotTransform;
+  entry.did_round_out = did_round_out;
   transform_stack_.emplace_back(entry);
 
   // The current clip aiks clip culling can not handle image filters.
@@ -484,10 +521,15 @@ bool ExperimentalCanvas::Restore() {
   // to be overly conservative, but we need to jump the depth to
   // the clip depth so that the next rendering op will get a
   // larger depth (it will pre-increment the current_depth_ value).
-  FML_CHECK(current_depth_ <= transform_stack_.back().clip_depth)
+  FML_DCHECK(current_depth_ <= transform_stack_.back().clip_depth)
       << current_depth_ << " <=? " << transform_stack_.back().clip_depth;
   current_depth_ = transform_stack_.back().clip_depth;
 
+  if (IsSkipping()) {
+    transform_stack_.pop_back();
+    return true;
+  }
+
   if (transform_stack_.back().rendering_mode ==
           Entity::RenderingMode::kSubpassAppendSnapshotTransform ||
       transform_stack_.back().rendering_mode ==
@@ -499,12 +541,13 @@ bool ExperimentalCanvas::Restore() {
 
     SaveLayerState save_layer_state = save_layer_state_.back();
     save_layer_state_.pop_back();
+    auto global_pass_position = GetGlobalPassPosition();
 
     std::shared_ptr<Contents> contents =
         PaintPassDelegate(save_layer_state.paint)
             .CreateContentsForSubpassTarget(
                 lazy_render_pass.inline_pass_context->GetTexture(),
-                Matrix::MakeTranslation(Vector3{-GetGlobalPassPosition()}) *
+                Matrix::MakeTranslation(Vector3{-global_pass_position}) *
                     transform_stack_.back().transform);
 
     lazy_render_pass.inline_pass_context->EndPass();
@@ -514,16 +557,19 @@ bool ExperimentalCanvas::Restore() {
     // sampling, so aligning here is important for avoiding visual nearest
     // sampling errors caused by limited floating point precision when
     // straddling a half pixel boundary.
-    //
-    // We do this in lieu of expanding/rounding out the subpass coverage in
-    // order to keep the bounds wrapping consistently tight around subpass
-    // elements. Which is necessary to avoid intense flickering in cases
-    // where a subpass texture has a large blur filter with clamp sampling.
-    //
-    // See also this bug: https://github.com/flutter/flutter/issues/144213
-    Point subpass_texture_position =
-        (save_layer_state.coverage.GetOrigin() - GetGlobalPassPosition())
-            .Round();
+    Point subpass_texture_position;
+    if (transform_stack_.back().did_round_out) {
+      // Subpass coverage was rounded out, origin potentially moved "down" by
+      // as much as a pixel.
+      subpass_texture_position =
+          (save_layer_state.coverage.GetOrigin() - global_pass_position)
+              .Floor();
+    } else {
+      // Subpass coverage was truncated. Pick the closest phyiscal pixel.
+      subpass_texture_position =
+          (save_layer_state.coverage.GetOrigin() - global_pass_position)
+              .Round();
+    }
 
     Entity element_entity;
     element_entity.SetClipDepth(++current_depth_);
@@ -545,9 +591,9 @@ bool ExperimentalCanvas::Restore() {
         // to the render target texture so far need to execute before it's bound
         // for blending (otherwise the blend pass will end up executing before
         // all the previous commands in the active pass).
-        auto input_texture = FlipBackdrop(
-            render_passes_, GetGlobalPassPosition(),
-            element_entity.GetClipDepth(), clip_coverage_stack_, renderer_);
+        auto input_texture =
+            FlipBackdrop(render_passes_, GetGlobalPassPosition(),
+                         clip_coverage_stack_, renderer_);
         if (!input_texture) {
           return false;
         }
@@ -670,6 +716,10 @@ void ExperimentalCanvas::DrawTextFrame(
 
 void ExperimentalCanvas::AddRenderEntityToCurrentPass(Entity entity,
                                                       bool reuse_depth) {
+  if (IsSkipping()) {
+    return;
+  }
+
   entity.SetTransform(
       Matrix::MakeTranslation(Vector3(-GetGlobalPassPosition())) *
       entity.GetTransform());
@@ -708,7 +758,7 @@ void ExperimentalCanvas::AddRenderEntityToCurrentPass(Entity entity,
   // We can render at a depth up to and including the depth of the currently
   // active clips and we will still be clipped out, but we cannot render at
   // a depth that is greater than the current clips or we will not be clipped.
-  FML_CHECK(current_depth_ <= transform_stack_.back().clip_depth)
+  FML_DCHECK(current_depth_ <= transform_stack_.back().clip_depth)
       << current_depth_ << " <=? " << transform_stack_.back().clip_depth;
   entity.SetClipDepth(current_depth_);
 
@@ -725,9 +775,8 @@ void ExperimentalCanvas::AddRenderEntityToCurrentPass(Entity entity,
       // to the render target texture so far need to execute before it's bound
       // for blending (otherwise the blend pass will end up executing before
       // all the previous commands in the active pass).
-      auto input_texture =
-          FlipBackdrop(render_passes_, GetGlobalPassPosition(),
-                       entity.GetClipDepth(), clip_coverage_stack_, renderer_);
+      auto input_texture = FlipBackdrop(render_passes_, GetGlobalPassPosition(),
+                                        clip_coverage_stack_, renderer_);
       if (!input_texture) {
         return;
       }
@@ -763,6 +812,10 @@ void ExperimentalCanvas::AddRenderEntityToCurrentPass(Entity entity,
 }
 
 void ExperimentalCanvas::AddClipEntityToCurrentPass(Entity entity) {
+  if (IsSkipping()) {
+    return;
+  }
+
   auto transform = entity.GetTransform();
   entity.SetTransform(
       Matrix::MakeTranslation(Vector3(-GetGlobalPassPosition())) * transform);
@@ -777,7 +830,7 @@ void ExperimentalCanvas::AddClipEntityToCurrentPass(Entity entity) {
   // to know if a clip will actually be used in advance of storing it in
   // the DisplayList buffer.
   // See https://github.com/flutter/flutter/issues/147021
-  FML_CHECK(current_depth_ <= transform_stack_.back().clip_depth)
+  FML_DCHECK(current_depth_ <= transform_stack_.back().clip_depth)
       << current_depth_ << " <=? " << transform_stack_.back().clip_depth;
   entity.SetClipDepth(transform_stack_.back().clip_depth);