[Impeller] Switch from AIKS canvas to DL based canvas implementation. (…

…flutter#53781)

The first part of switching Impeller/Aiks to using the display list instead of re-recording rendering operations. This should eventually let us cut CPU overhead of the raster thread for complex applications, though it should have no impact on GPU performance.

This does introduce a GLES only rendering bug that I haven't had luck tracking down, but is almost certainly due to switching to DL computed depth values. I'd like to handle this as a follow up when we prioritize GLES. flutter/flutter#153504

Part of flutter/flutter#142054

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/aiks_playground.cc

@@ -75,10 +75,7 @@ bool AiksPlayground::ImGuiBegin(const char* name,
 
 bool AiksPlayground::OpenPlaygroundHere(
     const sk_sp<flutter::DisplayList>& list) {
-  DlDispatcher dispatcher;
-  list->Dispatch(dispatcher);
-  Picture picture = dispatcher.EndRecordingAsPicture();
-  return OpenPlaygroundHere(std::move(picture));
+  return OpenPlaygroundHere([list]() { return list; });
 }
 
 bool AiksPlayground::OpenPlaygroundHere(
@@ -91,12 +88,28 @@ bool AiksPlayground::OpenPlaygroundHere(
 
   return Playground::OpenPlaygroundHere(
       [&renderer, &callback](RenderTarget& render_target) -> bool {
+#if EXPERIMENTAL_CANVAS
+        auto display_list = callback();
+        TextFrameDispatcher collector(renderer.GetContentContext(), Matrix());
+        display_list->Dispatch(collector);
+
+        ExperimentalDlDispatcher impeller_dispatcher(
+            renderer.GetContentContext(), render_target,
+            display_list->root_has_backdrop_filter(),
+            display_list->max_root_blend_mode(), IRect::MakeMaximum());
+        display_list->Dispatch(impeller_dispatcher);
+        impeller_dispatcher.FinishRecording();
+        renderer.GetContentContext().GetTransientsBuffer().Reset();
+        renderer.GetContentContext().GetLazyGlyphAtlas()->ResetTextFrames();
+        return true;
+#else
         auto display_list = callback();
         DlDispatcher dispatcher;
         display_list->Dispatch(dispatcher);
         Picture picture = dispatcher.EndRecordingAsPicture();
 
         return renderer.Render(picture, render_target, true);
+#endif  // EXPERIMENTAL_CANVAS
       });
 }
 

impeller/aiks/canvas.cc

@@ -813,7 +813,8 @@ void Canvas::SaveLayer(const Paint& paint,
                        const std::shared_ptr<ImageFilter>& backdrop_filter,
                        ContentBoundsPromise bounds_promise,
                        uint32_t total_content_depth,
-                       bool can_distribute_opacity) {
+                       bool can_distribute_opacity,
+                       bool bounds_from_caller) {
   if (can_distribute_opacity && !backdrop_filter &&
       Paint::CanApplyOpacityPeephole(paint) &&
       bounds_promise != ContentBoundsPromise::kMayClipContents) {

impeller/aiks/canvas.h

@@ -77,7 +77,8 @@ class Canvas {
       const std::shared_ptr<ImageFilter>& backdrop_filter = nullptr,
       ContentBoundsPromise bounds_promise = ContentBoundsPromise::kUnknown,
       uint32_t total_content_depth = kMaxDepth,
-      bool can_distribute_opacity = false);
+      bool can_distribute_opacity = false,
+      bool bounds_from_caller = false);
 
   virtual bool Restore();
 

impeller/aiks/experimental_canvas.cc

@@ -4,6 +4,7 @@
 
 #include "impeller/aiks/experimental_canvas.h"
 #include "fml/logging.h"
+#include "fml/trace_event.h"
 #include "impeller/aiks/canvas.h"
 #include "impeller/aiks/paint_pass_delegate.h"
 #include "impeller/base/validation.h"
@@ -82,26 +83,28 @@ static std::shared_ptr<Texture> FlipBackdrop(
     // unbalanced save layers. Ideally, this method would return false and the
     // renderer could handle that by terminating dispatch.
     render_passes.push_back(LazyRenderingConfig(
-        renderer, std::move(rendering_config.entity_pass_target)));
+        renderer, std::move(rendering_config.entity_pass_target),
+        std::move(rendering_config.inline_pass_context)));
     return nullptr;
   }
 
   std::shared_ptr<Texture> input_texture =
-      rendering_config.entity_pass_target->Flip(
-          *renderer.GetContext()->GetResourceAllocator());
+      rendering_config.inline_pass_context->GetTexture();
 
   if (!input_texture) {
     VALIDATION_LOG << "Failed to fetch the color texture in order to "
                       "apply an advanced blend or backdrop filter.";
 
     // Note: see above.
     render_passes.push_back(LazyRenderingConfig(
-        renderer, std::move(rendering_config.entity_pass_target)));
+        renderer, std::move(rendering_config.entity_pass_target),
+        std::move(rendering_config.inline_pass_context)));
     return nullptr;
   }
 
   render_passes.push_back(LazyRenderingConfig(
-      renderer, std::move(rendering_config.entity_pass_target)));
+      renderer, std::move(rendering_config.entity_pass_target),
+      std::move(rendering_config.inline_pass_context)));
   // Eagerly restore the BDF contents.
 
   // If the pass context returns a backdrop texture, we need to draw it to the
@@ -157,7 +160,6 @@ static const constexpr RenderTarget::AttachmentConfig kDefaultStencilConfig =
 static std::unique_ptr<EntityPassTarget> CreateRenderTarget(
     ContentContext& renderer,
     ISize size,
-    int mip_count,
     const Color& clear_color) {
   const std::shared_ptr<Context>& context = renderer.GetContext();
 
@@ -166,18 +168,12 @@ static std::unique_ptr<EntityPassTarget> CreateRenderTarget(
   /// What's important is the `StorageMode` of the textures, which cannot be
   /// changed for the lifetime of the textures.
 
-  if (context->GetBackendType() == Context::BackendType::kOpenGLES) {
-    // TODO(https://github.com/flutter/flutter/issues/141732): Implement mip map
-    // generation on opengles.
-    mip_count = 1;
-  }
-
   RenderTarget target;
   if (context->GetCapabilities()->SupportsOffscreenMSAA()) {
     target = renderer.GetRenderTargetCache()->CreateOffscreenMSAA(
         /*context=*/*context,
         /*size=*/size,
-        /*mip_count=*/mip_count,
+        /*mip_count=*/1,
         /*label=*/"EntityPass",
         /*color_attachment_config=*/
         RenderTarget::AttachmentConfigMSAA{
@@ -191,7 +187,7 @@ static std::unique_ptr<EntityPassTarget> CreateRenderTarget(
     target = renderer.GetRenderTargetCache()->CreateOffscreen(
         *context,  // context
         size,      // size
-        /*mip_count=*/mip_count,
+        /*mip_count=*/1,
         "EntityPass",  // label
         RenderTarget::AttachmentConfig{
             .storage_mode = StorageMode::kDevicePrivate,
@@ -273,12 +269,10 @@ void ExperimentalCanvas::SetupRenderPass() {
   // a second save layer with the same dimensions as the onscreen. When
   // rendering is completed, we must blit this saveLayer to the onscreen.
   if (requires_readback_) {
-    auto entity_pass_target = CreateRenderTarget(
-        renderer_,                  //
-        color0.texture->GetSize(),  //
-        // Note: this is incorrect, we also need to know what kind of filter.
-        /*mip_count=*/4,  //
-        /*clear_color=*/Color::BlackTransparent());
+    auto entity_pass_target =
+        CreateRenderTarget(renderer_,                  //
+                           color0.texture->GetSize(),  //
+                           /*clear_color=*/Color::BlackTransparent());
     render_passes_.push_back(
         LazyRenderingConfig(renderer_, std::move(entity_pass_target)));
   } else {
@@ -312,47 +306,54 @@ void ExperimentalCanvas::SaveLayer(
     const std::shared_ptr<ImageFilter>& backdrop_filter,
     ContentBoundsPromise bounds_promise,
     uint32_t total_content_depth,
-    bool can_distribute_opacity) {
-  // Can we always guarantee that we get a bounds? Does a lack of bounds
-  // indicate something?
-  if (!bounds.has_value()) {
-    bounds = Rect::MakeSize(render_target_.GetRenderTargetSize());
+    bool can_distribute_opacity,
+    bool bounds_from_caller) {
+  TRACE_EVENT0("flutter", "Canvas::saveLayer");
+
+  if (bounds.has_value() && bounds->IsEmpty()) {
+    Save(total_content_depth);
+    return;
+  }
+
+  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;
   }
 
-  // SaveLayer is a no-op, depending on the bounds promise. Should/Can DL elide
-  // this?
-  if (bounds->IsEmpty()) {
+  auto maybe_current_clip_coverage = clip_coverage_stack_.CurrentClipCoverage();
+  if (!maybe_current_clip_coverage.has_value()) {
     Save(total_content_depth);
     return;
   }
+  auto current_clip_coverage = maybe_current_clip_coverage.value();
 
   // The maximum coverage of the subpass. Subpasses textures should never
   // extend outside the parent pass texture or the current clip coverage.
-  Rect coverage_limit = Rect::MakeOriginSize(
-      GetGlobalPassPosition(),
-      Size(render_passes_.back().inline_pass_context->GetTexture()->GetSize()));
+  std::optional<Rect> maybe_coverage_limit =
+      Rect::MakeOriginSize(GetGlobalPassPosition(),
+                           Size(render_passes_.back()
+                                    .inline_pass_context->GetTexture()
+                                    ->GetSize()))
+          .Intersection(current_clip_coverage);
+
+  if (!maybe_coverage_limit.has_value()) {
+    Save(total_content_depth);
+    return;
+  }
+  maybe_coverage_limit = maybe_coverage_limit->Intersection(
+      Rect::MakeSize(render_target_.GetRenderTargetSize()));
 
-  // BDF No-op. need to do some precomputation to ensure this is fully skipped.
-  if (backdrop_filter) {
-    if (!clip_coverage_stack_.HasCoverage()) {
-      Save(total_content_depth);
-      return;
-    }
-    auto maybe_clip_coverage = clip_coverage_stack_.CurrentClipCoverage();
-    if (!maybe_clip_coverage.has_value()) {
-      Save(total_content_depth);
-      return;
-    }
-    auto clip_coverage = maybe_clip_coverage.value();
-    if (clip_coverage.IsEmpty() ||
-        !coverage_limit.IntersectsWithRect(clip_coverage)) {
-      Save(total_content_depth);
-      return;
-    }
+  if (!maybe_coverage_limit.has_value() || maybe_coverage_limit->IsEmpty()) {
+    Save(total_content_depth);
+    return;
   }
+  auto coverage_limit = maybe_coverage_limit.value();
 
   if (can_distribute_opacity && !backdrop_filter &&
-      Paint::CanApplyOpacityPeephole(paint)) {
+      Paint::CanApplyOpacityPeephole(paint) &&
+      bounds_promise != ContentBoundsPromise::kMayClipContents) {
     Save(total_content_depth);
     transform_stack_.back().distributed_opacity *= paint.color.alpha;
     return;
@@ -362,11 +363,8 @@ void ExperimentalCanvas::SaveLayer(
   std::shared_ptr<FilterContents> backdrop_filter_contents;
   Point local_position = {0, 0};
   if (backdrop_filter) {
-    auto current_clip_coverage = clip_coverage_stack_.CurrentClipCoverage();
-    if (current_clip_coverage.has_value()) {
-      local_position =
-          current_clip_coverage->GetOrigin() - GetGlobalPassPosition();
-    }
+    local_position =
+        current_clip_coverage.GetOrigin() - GetGlobalPassPosition();
     EntityPass::BackdropFilterProc backdrop_filter_proc =
         [backdrop_filter = backdrop_filter->Clone()](
             const FilterInput::Ref& input, const Matrix& effect_transform,
@@ -401,23 +399,25 @@ void ExperimentalCanvas::SaveLayer(
 
   // Backdrop Filter must expand bounds to at least the clip stack, otherwise
   // the coverage of the parent render pass.
-  Rect subpass_coverage = bounds->TransformBounds(GetCurrentTransform());
-  if (backdrop_filter_contents) {
-    FML_CHECK(clip_coverage_stack_.HasCoverage());
-    // We should never hit this case as we check the intersection above.
-    // NOLINTBEGIN(bugprone-unchecked-optional-access)
-    subpass_coverage =
-        coverage_limit
-            .Intersection(clip_coverage_stack_.CurrentClipCoverage().value())
-            .value();
-    // NOLINTEND(bugprone-unchecked-optional-access)
+  Rect subpass_coverage;
+  if (backdrop_filter_contents ||
+      Entity::IsBlendModeDestructive(paint.blend_mode) || !bounds.has_value()) {
+    subpass_coverage = coverage_limit;
+    // TODO(jonahwilliams): if we have tight bounds we should be able to reduce
+    // this size here. if (bounds.has_value() && bounds_from_caller) {
+    //   subpass_coverage =
+    //       coverage_limit.Intersection(bounds.value()).value_or(bounds.value());
+    // }
+  } else {
+    subpass_coverage = bounds->TransformBounds(GetCurrentTransform());
   }
 
   render_passes_.push_back(LazyRenderingConfig(
       renderer_,                                             //
       CreateRenderTarget(renderer_,                          //
                          ISize(subpass_coverage.GetSize()),  //
-                         1u, Color::BlackTransparent())));
+                         Color::BlackTransparent()           //
+                         )));
   save_layer_state_.push_back(SaveLayerState{paint_copy, subpass_coverage});
 
   CanvasStackEntry entry;
@@ -491,7 +491,8 @@ bool ExperimentalCanvas::Restore() {
         PaintPassDelegate(save_layer_state.paint)
             .CreateContentsForSubpassTarget(
                 lazy_render_pass.inline_pass_context->GetTexture(),
-                transform_stack_.back().transform);
+                Matrix::MakeTranslation(Vector3{-GetGlobalPassPosition()}) *
+                    transform_stack_.back().transform);
 
     lazy_render_pass.inline_pass_context->EndPass();
 
@@ -669,20 +670,22 @@ void ExperimentalCanvas::AddRenderEntityToCurrentPass(Entity entity,
   // conditionally update the backdrop color to its solid color value blended
   // with the current backdrop.
   if (render_passes_.back().IsApplyingClearColor()) {
-    std::optional<Color> maybe_color =
-        entity.AsBackgroundColor(render_passes_.back()
-                                     .entity_pass_target->GetRenderTarget()
-                                     .GetRenderTargetSize());
+    std::optional<Color> maybe_color = entity.AsBackgroundColor(
+        render_passes_.back().inline_pass_context->GetTexture()->GetSize());
     if (maybe_color.has_value()) {
       Color color = maybe_color.value();
-      RenderTarget& render_target =
-          render_passes_.back().entity_pass_target->GetRenderTarget();
+      RenderTarget& render_target = render_passes_.back()
+                                        .inline_pass_context->GetPassTarget()
+                                        .GetRenderTarget();
       ColorAttachment attachment =
           render_target.GetColorAttachments().find(0u)->second;
+      // Attachment.clear color needs to be premultiplied at all times, but the
+      // Color::Blend function requires unpremultiplied colors.
       attachment.clear_color = attachment.clear_color.Unpremultiply()
                                    .Blend(color, entity.GetBlendMode())
                                    .Premultiply();
       render_target.SetColorAttachment(attachment, 0u);
+      return;
     }
   }
 
@@ -700,8 +703,36 @@ void ExperimentalCanvas::AddRenderEntityToCurrentPass(Entity entity,
     if (renderer_.GetDeviceCapabilities().SupportsFramebufferFetch()) {
       ApplyFramebufferBlend(entity);
     } else {
-      VALIDATION_LOG << "Emulated advanced blends are currently unsupported.";
-      return;
+      // End the active pass and flush the buffer before rendering "advanced"
+      // blends. Advanced blends work by binding the current render target
+      // texture as an input ("destination"), blending with a second texture
+      // input ("source"), writing the result to an intermediate texture, and
+      // finally copying the data from the intermediate texture back to the
+      // render target texture. And so all of the commands that have written
+      // 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(),
+                                        clip_coverage_stack_, renderer_);
+      if (!input_texture) {
+        return;
+      }
+
+      // The coverage hint tells the rendered Contents which portion of the
+      // rendered output will actually be used, and so we set this to the
+      // current clip coverage (which is the max clip bounds). The contents may
+      // optionally use this hint to avoid unnecessary rendering work.
+      auto element_coverage_hint = entity.GetContents()->GetCoverageHint();
+      entity.GetContents()->SetCoverageHint(Rect::Intersection(
+          element_coverage_hint, clip_coverage_stack_.CurrentClipCoverage()));
+
+      FilterInput::Vector inputs = {
+          FilterInput::Make(input_texture, entity.GetTransform().Invert()),
+          FilterInput::Make(entity.GetContents())};
+      auto contents =
+          ColorFilterContents::MakeBlend(entity.GetBlendMode(), inputs);
+      entity.SetContents(std::move(contents));
+      entity.SetBlendMode(BlendMode::kSource);
     }
   }
 
@@ -831,6 +862,7 @@ bool ExperimentalCanvas::BlitToOnscreen() {
 
 void ExperimentalCanvas::EndReplay() {
   FML_DCHECK(render_passes_.size() == 1u);
+  render_passes_.back().inline_pass_context->GetRenderPass(0);
   render_passes_.back().inline_pass_context->EndPass();
 
   // If requires_readback_ was true, then we rendered to an offscreen texture