[Impeller] port clip stack fixes to new canvas. (#54727)

From c99eda4

Author: Jonah Williams

impeller/aiks/experimental_canvas.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "impeller/aiks/experimental_canvas.h"
+#include <limits>
 #include "fml/logging.h"
 #include "fml/trace_event.h"
 #include "impeller/aiks/canvas.h"
@@ -57,6 +58,7 @@ 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());
@@ -132,16 +134,21 @@ static std::shared_ptr<Texture> FlipBackdrop(
 
   // Restore any clips that were recorded before the backdrop filter was
   // applied.
-  auto& replay_entities = clip_coverage_stack.GetReplayEntities();
-  for (const auto& replay : replay_entities) {
+  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;
     SetClipScissor(
-        clip_coverage_stack.CurrentClipCoverage(),
+        next_replay_clip->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 restore.";
+      VALIDATION_LOG << "Failed to render entity for clip replay.";
     }
   }
 
@@ -375,8 +382,12 @@ void ExperimentalCanvas::SaveLayer(
           return filter;
         };
 
-    auto input_texture = FlipBackdrop(render_passes_, GetGlobalPassPosition(),
-                                      clip_coverage_stack_, renderer_);
+    auto input_texture = FlipBackdrop(render_passes_,                        //
+                                      GetGlobalPassPosition(),               //
+                                      std::numeric_limits<uint32_t>::max(),  //
+                                      clip_coverage_stack_,                  //
+                                      renderer_                              //
+    );
     if (!input_texture) {
       // Validation failures are logged in FlipBackdrop.
       return;
@@ -532,9 +543,9 @@ 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(),
-                         clip_coverage_stack_, renderer_);
+        auto input_texture = FlipBackdrop(
+            render_passes_, GetGlobalPassPosition(),
+            element_entity.GetClipDepth(), clip_coverage_stack_, renderer_);
         if (!input_texture) {
           return false;
         }
@@ -712,8 +723,9 @@ 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(),
-                                        clip_coverage_stack_, renderer_);
+      auto input_texture =
+          FlipBackdrop(render_passes_, GetGlobalPassPosition(),
+                       entity.GetClipDepth(), clip_coverage_stack_, renderer_);
       if (!input_texture) {
         return;
       }

impeller/entity/entity_pass.cc

@@ -852,7 +852,8 @@ bool EntityPass::RenderElement(Entity& element_entity,
   // 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(element_entity)) {
+             clip_coverage_stack.GetNextReplayResult(
+                 element_entity.GetClipDepth())) {
     auto& replay_entity = next_replay_clip->entity;
     SetClipScissor(next_replay_clip->clip_coverage, *result.pass,
                    global_pass_position);

impeller/entity/entity_pass_clip_stack.cc

@@ -178,15 +178,15 @@ void EntityPassClipStack::ActivateClipReplay() {
 }
 
 const EntityPassClipStack::ReplayResult*
-EntityPassClipStack::GetNextReplayResult(const Entity& entity) {
+EntityPassClipStack::GetNextReplayResult(size_t current_clip_depth) {
   if (next_replay_index_ >=
       subpass_state_.back().rendered_clip_entities.size()) {
     // No clips need to be replayed.
     return nullptr;
   }
   ReplayResult* next_replay =
       &subpass_state_.back().rendered_clip_entities[next_replay_index_];
-  if (next_replay->entity.GetClipDepth() < entity.GetClipDepth()) {
+  if (next_replay->entity.GetClipDepth() < current_clip_depth) {
     // The next replay clip doesn't affect the current entity, so don't replay
     // it yet.
     return nullptr;

impeller/entity/entity_pass_clip_stack.h

@@ -68,7 +68,7 @@ class EntityPassClipStack {
 
   /// @brief Returns the next Entity that should be replayed. If there are no
   ///        enities to replay, then nullptr is returned.
-  const ReplayResult* GetNextReplayResult(const Entity& entity);
+  const ReplayResult* GetNextReplayResult(size_t current_clip_depth);
 
   // Visible for testing.
   const std::vector<ClipCoverageLayer> GetClipCoverageLayers() const;