From cce2ee3fb81cf896fbace27a94b3f6cae4ddd5e7 Mon Sep 17 00:00:00 2001
From: Dan Field <dnfield@google.com>
Date: Thu, 25 Aug 2022 07:21:23 -0700
Subject: [PATCH] [Impeller] Render on Simulator (flutter/engine#35692)

---
 engine/src/flutter/flow/surface_frame.cc      |  5 ++-
 .../flutter/flow/surface_frame_unittests.cc   | 12 +++++++
 .../renderer/backend/metal/render_pass_mtl.mm | 31 +++++++++++++------
 .../src/flutter/impeller/renderer/platform.h  |  2 +-
 4 files changed, 37 insertions(+), 13 deletions(-)

diff --git a/engine/src/flutter/flow/surface_frame.cc b/engine/src/flutter/flow/surface_frame.cc
index c8a6bbf6bc3..d3133daa073 100644
--- a/engine/src/flutter/flow/surface_frame.cc
+++ b/engine/src/flutter/flow/surface_frame.cc
@@ -6,6 +6,7 @@
 
 #include <limits>
 
+#include "flutter/flow/layers/layer.h"
 #include "flutter/fml/logging.h"
 #include "flutter/fml/trace_event.h"
 #include "third_party/skia/include/utils/SkNWayCanvas.h"
@@ -25,9 +26,7 @@ SurfaceFrame::SurfaceFrame(sk_sp<SkSurface> surface,
   if (surface_) {
     canvas_ = surface_->getCanvas();
   } else if (display_list_fallback) {
-    dl_recorder_ = sk_make_sp<DisplayListCanvasRecorder>(
-        SkRect::MakeWH(std::numeric_limits<SkScalar>::max(),
-                       std::numeric_limits<SkScalar>::max()));
+    dl_recorder_ = sk_make_sp<DisplayListCanvasRecorder>(kGiantRect);
     canvas_ = dl_recorder_.get();
   }
 }
diff --git a/engine/src/flutter/flow/surface_frame_unittests.cc b/engine/src/flutter/flow/surface_frame_unittests.cc
index c7a0bc5132a..7bc4d07ef56 100644
--- a/engine/src/flutter/flow/surface_frame_unittests.cc
+++ b/engine/src/flutter/flow/surface_frame_unittests.cc
@@ -20,4 +20,16 @@ TEST(FlowTest, SurfaceFrameDoesNotSubmitInDtor) {
   surface_frame.reset();
 }
 
+TEST(FlowTest, SurfaceFrameDoesNotHaveEmptyCanvas) {
+  SurfaceFrame::FramebufferInfo framebuffer_info;
+  SurfaceFrame frame(
+      /*surface=*/nullptr, framebuffer_info,
+      /*submit_callback=*/[](const SurfaceFrame&, SkCanvas*) { return true; },
+      /*context_result=*/nullptr, /*display_list_fallback=*/true);
+
+  EXPECT_FALSE(frame.SkiaCanvas()->getLocalClipBounds().isEmpty());
+  EXPECT_FALSE(
+      frame.SkiaCanvas()->quickReject(SkRect::MakeLTRB(10, 10, 50, 50)));
+}
+
 }  // namespace flutter
diff --git a/engine/src/flutter/impeller/renderer/backend/metal/render_pass_mtl.mm b/engine/src/flutter/impeller/renderer/backend/metal/render_pass_mtl.mm
index c277bbb5056..e8c825af36b 100644
--- a/engine/src/flutter/impeller/renderer/backend/metal/render_pass_mtl.mm
+++ b/engine/src/flutter/impeller/renderer/backend/metal/render_pass_mtl.mm
@@ -493,18 +493,31 @@ bool RenderPassMTL::EncodeCommands(const std::shared_ptr<Allocator>& allocator,
     if (!mtl_index_buffer) {
       return false;
     }
+
     FML_DCHECK(command.index_count *
                    (command.index_type == IndexType::k16bit ? 2 : 4) ==
                command.index_buffer.range.length);
-    // Returns void. All error checking must be done by this point.
-    [encoder drawIndexedPrimitives:ToMTLPrimitiveType(command.primitive_type)
-                        indexCount:command.index_count
-                         indexType:ToMTLIndexType(command.index_type)
-                       indexBuffer:mtl_index_buffer
-                 indexBufferOffset:command.index_buffer.range.offset
-                     instanceCount:command.instance_count
-                        baseVertex:command.base_vertex
-                      baseInstance:0u];
+
+    if (command.instance_count != 1u) {
+#if TARGET_OS_SIMULATOR
+      VALIDATION_LOG << "iOS Simulator does not support instanced rendering.";
+      return false;
+#endif
+      [encoder drawIndexedPrimitives:ToMTLPrimitiveType(command.primitive_type)
+                          indexCount:command.index_count
+                           indexType:ToMTLIndexType(command.index_type)
+                         indexBuffer:mtl_index_buffer
+                   indexBufferOffset:command.index_buffer.range.offset
+                       instanceCount:command.instance_count
+                          baseVertex:command.base_vertex
+                        baseInstance:0u];
+    } else {
+      [encoder drawIndexedPrimitives:ToMTLPrimitiveType(command.primitive_type)
+                          indexCount:command.index_count
+                           indexType:ToMTLIndexType(command.index_type)
+                         indexBuffer:mtl_index_buffer
+                   indexBufferOffset:command.index_buffer.range.offset];
+    }
   }
   return true;
 }
diff --git a/engine/src/flutter/impeller/renderer/platform.h b/engine/src/flutter/impeller/renderer/platform.h
index c2783d7581e..6076e810b3d 100644
--- a/engine/src/flutter/impeller/renderer/platform.h
+++ b/engine/src/flutter/impeller/renderer/platform.h
@@ -12,7 +12,7 @@
 namespace impeller {
 
 constexpr size_t DefaultUniformAlignment() {
-#if FML_OS_IOS
+#if FML_OS_IOS && !TARGET_OS_SIMULATOR
   return 16u;
 #elif FML_OS_MACOSX
   return 256u;