Add an overlay surface on top of embedded UIViews.

ci/licenses_golden/licenses_flutter

@@ -597,6 +597,8 @@ FILE: ../../../flutter/shell/platform/darwin/ios/framework/Headers/FlutterPlatfo
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Headers/FlutterPluginAppLifeCycleDelegate.h
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterCallbackCache.mm
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterCallbackCache_Internal.h
+FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterOverlayView.h
+FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterOverlayView.mm
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterPluginAppLifeCycleDelegate.mm
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/accessibility_text_entry.h
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/accessibility_text_entry.mm

flow/embedded_views.h

@@ -6,6 +6,7 @@
 #define FLUTTER_FLOW_EMBEDDED_VIEWS_H_
 
 #include "flutter/fml/memory/ref_counted.h"
+#include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkPoint.h"
 #include "third_party/skia/include/core/SkSize.h"
 
@@ -15,6 +16,7 @@ class EmbeddedViewParams {
  public:
   SkPoint offsetPixels;
   SkSize sizePoints;
+  SkISize canvasBaseLayerSize;
 };
 
 // This is only used on iOS when running in a non headless mode,
@@ -25,8 +27,8 @@ class ExternalViewEmbedder {
   ExternalViewEmbedder() = default;
 
   // Must be called on the UI thread.
-  virtual void CompositeEmbeddedView(int view_id,
-                                     const EmbeddedViewParams& params) {}
+  virtual SkCanvas* CompositeEmbeddedView(int view_id,
+                                          const EmbeddedViewParams& params) = 0;
 
   virtual ~ExternalViewEmbedder() = default;
 

flow/layers/clip_path_layer.cc

@@ -50,14 +50,14 @@ void ClipPathLayer::Paint(PaintContext& context) const {
   TRACE_EVENT0("flutter", "ClipPathLayer::Paint");
   FML_DCHECK(needs_painting());
 
-  SkAutoCanvasRestore save(&context.canvas, true);
-  context.canvas.clipPath(clip_path_, clip_behavior_ != Clip::hardEdge);
+  SkAutoCanvasRestore save(context.canvas, true);
+  context.canvas->clipPath(clip_path_, clip_behavior_ != Clip::hardEdge);
   if (clip_behavior_ == Clip::antiAliasWithSaveLayer) {
-    context.canvas.saveLayer(paint_bounds(), nullptr);
+    context.canvas->saveLayer(paint_bounds(), nullptr);
   }
   PaintChildren(context);
   if (clip_behavior_ == Clip::antiAliasWithSaveLayer) {
-    context.canvas.restore();
+    context.canvas->restore();
   }
 }
 

flow/layers/clip_rect_layer.cc

@@ -41,14 +41,14 @@ void ClipRectLayer::Paint(PaintContext& context) const {
   TRACE_EVENT0("flutter", "ClipRectLayer::Paint");
   FML_DCHECK(needs_painting());
 
-  SkAutoCanvasRestore save(&context.canvas, true);
-  context.canvas.clipRect(paint_bounds(), clip_behavior_ != Clip::hardEdge);
+  SkAutoCanvasRestore save(context.canvas, true);
+  context.canvas->clipRect(paint_bounds(), clip_behavior_ != Clip::hardEdge);
   if (clip_behavior_ == Clip::antiAliasWithSaveLayer) {
-    context.canvas.saveLayer(paint_bounds(), nullptr);
+    context.canvas->saveLayer(paint_bounds(), nullptr);
   }
   PaintChildren(context);
   if (clip_behavior_ == Clip::antiAliasWithSaveLayer) {
-    context.canvas.restore();
+    context.canvas->restore();
   }
 }
 

flow/layers/clip_rrect_layer.cc

@@ -48,14 +48,14 @@ void ClipRRectLayer::Paint(PaintContext& context) const {
   TRACE_EVENT0("flutter", "ClipRRectLayer::Paint");
   FML_DCHECK(needs_painting());
 
-  SkAutoCanvasRestore save(&context.canvas, true);
-  context.canvas.clipRRect(clip_rrect_, clip_behavior_ != Clip::hardEdge);
+  SkAutoCanvasRestore save(context.canvas, true);
+  context.canvas->clipRRect(clip_rrect_, clip_behavior_ != Clip::hardEdge);
   if (clip_behavior_ == Clip::antiAliasWithSaveLayer) {
-    context.canvas.saveLayer(paint_bounds(), nullptr);
+    context.canvas->saveLayer(paint_bounds(), nullptr);
   }
   PaintChildren(context);
   if (clip_behavior_ == Clip::antiAliasWithSaveLayer) {
-    context.canvas.restore();
+    context.canvas->restore();
   }
 }
 

flow/layers/layer.cc

@@ -26,13 +26,13 @@ Layer::AutoSaveLayer::AutoSaveLayer(const PaintContext& paint_context,
                                     const SkRect& bounds,
                                     const SkPaint* paint)
     : paint_context_(paint_context), bounds_(bounds) {
-  paint_context_.canvas.saveLayer(bounds_, paint);
+  paint_context_.canvas->saveLayer(bounds_, paint);
 }
 
 Layer::AutoSaveLayer::AutoSaveLayer(const PaintContext& paint_context,
                                     const SkCanvas::SaveLayerRec& layer_rec)
     : paint_context_(paint_context), bounds_(*layer_rec.fBounds) {
-  paint_context_.canvas.saveLayer(layer_rec);
+  paint_context_.canvas->saveLayer(layer_rec);
 }
 
 Layer::AutoSaveLayer Layer::AutoSaveLayer::Create(
@@ -50,9 +50,9 @@ Layer::AutoSaveLayer Layer::AutoSaveLayer::Create(
 
 Layer::AutoSaveLayer::~AutoSaveLayer() {
   if (paint_context_.checkerboard_offscreen_layers) {
-    DrawCheckerboard(&paint_context_.canvas, bounds_);
+    DrawCheckerboard(paint_context_.canvas, bounds_);
   }
-  paint_context_.canvas.restore();
+  paint_context_.canvas->restore();
 }
 
 }  // namespace flow

flow/layers/layer.h

@@ -64,7 +64,7 @@ class Layer {
   virtual void Preroll(PrerollContext* context, const SkMatrix& matrix);
 
   struct PaintContext {
-    SkCanvas& canvas;
+    SkCanvas* canvas;
     ExternalViewEmbedder* view_embedder;
     const Stopwatch& frame_time;
     const Stopwatch& engine_time;

flow/layers/layer_tree.cc

@@ -67,7 +67,7 @@ void LayerTree::Paint(CompositorContext::ScopedFrame& frame,
                       bool ignore_raster_cache) const {
   TRACE_EVENT0("flutter", "LayerTree::Paint");
   Layer::PaintContext context = {
-      *frame.canvas(),
+      frame.canvas(),
       frame.view_embedder(),
       frame.context().frame_time(),
       frame.context().engine_time(),
@@ -107,7 +107,7 @@ sk_sp<SkPicture> LayerTree::Flatten(const SkRect& bounds) {
   };
 
   Layer::PaintContext paint_context = {
-      *canvas,  // canvas
+      canvas,  // canvas
       nullptr,
       unused_stopwatch,         // frame time (dont care)
       unused_stopwatch,         // engine time (dont care)

flow/layers/opacity_layer.cc

@@ -31,20 +31,20 @@ void OpacityLayer::Paint(PaintContext& context) const {
   SkPaint paint;
   paint.setAlpha(alpha_);
 
-  SkAutoCanvasRestore save(&context.canvas, true);
-  context.canvas.translate(offset_.fX, offset_.fY);
+  SkAutoCanvasRestore save(context.canvas, true);
+  context.canvas->translate(offset_.fX, offset_.fY);
 
 #ifndef SUPPORT_FRACTIONAL_TRANSLATION
-  context.canvas.setMatrix(
-      RasterCache::GetIntegralTransCTM(context.canvas.getTotalMatrix()));
+  context.canvas->setMatrix(
+      RasterCache::GetIntegralTransCTM(context.canvas->getTotalMatrix()));
 #endif
 
   if (layers().size() == 1 && context.raster_cache) {
-    const SkMatrix& ctm = context.canvas.getTotalMatrix();
+    const SkMatrix& ctm = context.canvas->getTotalMatrix();
     RasterCacheResult child_cache =
         context.raster_cache->Get(layers()[0].get(), ctm);
     if (child_cache.is_valid()) {
-      child_cache.draw(context.canvas, &paint);
+      child_cache.draw(*context.canvas, &paint);
       return;
     }
   }

flow/layers/performance_overlay_layer.cc

@@ -73,14 +73,14 @@ void PerformanceOverlayLayer::Paint(PaintContext& context) const {
   SkScalar y = paint_bounds().y() + padding;
   SkScalar width = paint_bounds().width() - (padding * 2);
   SkScalar height = paint_bounds().height() / 2;
-  SkAutoCanvasRestore save(&context.canvas, true);
+  SkAutoCanvasRestore save(context.canvas, true);
 
-  VisualizeStopWatch(context.canvas, context.frame_time, x, y, width,
+  VisualizeStopWatch(*context.canvas, context.frame_time, x, y, width,
                      height - padding,
                      options_ & kVisualizeRasterizerStatistics,
                      options_ & kDisplayRasterizerStatistics, "GPU");
 
-  VisualizeStopWatch(context.canvas, context.engine_time, x, y + height, width,
+  VisualizeStopWatch(*context.canvas, context.engine_time, x, y + height, width,
                      height - padding, options_ & kVisualizeEngineStatistics,
                      options_ & kDisplayEngineStatistics, "UI");
 }

flow/layers/physical_shape_layer.cc

@@ -83,28 +83,28 @@ void PhysicalShapeLayer::Paint(PaintContext& context) const {
   FML_DCHECK(needs_painting());
 
   if (elevation_ != 0) {
-    DrawShadow(&context.canvas, path_, shadow_color_, elevation_,
+    DrawShadow(context.canvas, path_, shadow_color_, elevation_,
                SkColorGetA(color_) != 0xff, device_pixel_ratio_);
   }
 
   // Call drawPath without clip if possible for better performance.
   SkPaint paint;
   paint.setColor(color_);
   if (clip_behavior_ != Clip::antiAliasWithSaveLayer) {
-    context.canvas.drawPath(path_, paint);
+    context.canvas->drawPath(path_, paint);
   }
 
-  int saveCount = context.canvas.save();
+  int saveCount = context.canvas->save();
   switch (clip_behavior_) {
     case Clip::hardEdge:
-      context.canvas.clipPath(path_, false);
+      context.canvas->clipPath(path_, false);
       break;
     case Clip::antiAlias:
-      context.canvas.clipPath(path_, true);
+      context.canvas->clipPath(path_, true);
       break;
     case Clip::antiAliasWithSaveLayer:
-      context.canvas.clipPath(path_, true);
-      context.canvas.saveLayer(paint_bounds(), nullptr);
+      context.canvas->clipPath(path_, true);
+      context.canvas->saveLayer(paint_bounds(), nullptr);
       break;
     case Clip::none:
       break;
@@ -115,12 +115,12 @@ void PhysicalShapeLayer::Paint(PaintContext& context) const {
     // (https://github.com/flutter/flutter/issues/18057#issue-328003931)
     // using saveLayer, we have to call drawPaint instead of drawPath as
     // anti-aliased drawPath will always have such artifacts.
-    context.canvas.drawPaint(paint);
+    context.canvas->drawPaint(paint);
   }
 
   PaintChildren(context);
 
-  context.canvas.restoreToCount(saveCount);
+  context.canvas->restoreToCount(saveCount);
 }
 
 void PhysicalShapeLayer::DrawShadow(SkCanvas* canvas,

flow/layers/picture_layer.cc

@@ -34,22 +34,22 @@ void PictureLayer::Paint(PaintContext& context) const {
   FML_DCHECK(picture_.get());
   FML_DCHECK(needs_painting());
 
-  SkAutoCanvasRestore save(&context.canvas, true);
-  context.canvas.translate(offset_.x(), offset_.y());
+  SkAutoCanvasRestore save(context.canvas, true);
+  context.canvas->translate(offset_.x(), offset_.y());
 #ifndef SUPPORT_FRACTIONAL_TRANSLATION
-  context.canvas.setMatrix(
-      RasterCache::GetIntegralTransCTM(context.canvas.getTotalMatrix()));
+  context.canvas->setMatrix(
+      RasterCache::GetIntegralTransCTM(context.canvas->getTotalMatrix()));
 #endif
 
   if (context.raster_cache) {
-    const SkMatrix& ctm = context.canvas.getTotalMatrix();
+    const SkMatrix& ctm = context.canvas->getTotalMatrix();
     RasterCacheResult result = context.raster_cache->Get(*picture(), ctm);
     if (result.is_valid()) {
-      result.draw(context.canvas);
+      result.draw(*context.canvas);
       return;
     }
   }
-  context.canvas.drawPicture(picture());
+  context.canvas->drawPicture(picture());
 }
 
 }  // namespace flow

flow/layers/platform_view_layer.cc

@@ -23,11 +23,16 @@ void PlatformViewLayer::Paint(PaintContext& context) const {
     return;
   }
   EmbeddedViewParams params;
-  SkMatrix transform = context.canvas.getTotalMatrix();
+  SkMatrix transform = context.canvas->getTotalMatrix();
   params.offsetPixels =
       SkPoint::Make(transform.getTranslateX(), transform.getTranslateY());
   params.sizePoints = size_;
+  params.canvasBaseLayerSize = context.canvas->getBaseLayerSize();
 
-  context.view_embedder->CompositeEmbeddedView(view_id_, params);
+  SkCanvas* canvas =
+      context.view_embedder->CompositeEmbeddedView(view_id_, params);
+  // TODO(amirh): copy the full canvas state here
+  canvas->concat(context.canvas->getTotalMatrix());
+  context.canvas = canvas;
 }
 }  // namespace flow

flow/layers/shader_mask_layer.cc

@@ -21,8 +21,8 @@ void ShaderMaskLayer::Paint(PaintContext& context) const {
   SkPaint paint;
   paint.setBlendMode(blend_mode_);
   paint.setShader(shader_);
-  context.canvas.translate(mask_rect_.left(), mask_rect_.top());
-  context.canvas.drawRect(
+  context.canvas->translate(mask_rect_.left(), mask_rect_.top());
+  context.canvas->drawRect(
       SkRect::MakeWH(mask_rect_.width(), mask_rect_.height()), paint);
 }
 

flow/layers/texture_layer.cc

@@ -23,7 +23,7 @@ void TextureLayer::Paint(PaintContext& context) const {
   if (!texture) {
     return;
   }
-  texture->Paint(context.canvas, paint_bounds(), freeze_);
+  texture->Paint(*context.canvas, paint_bounds(), freeze_);
 }
 
 }  // namespace flow

flow/layers/transform_layer.cc

@@ -36,8 +36,8 @@ void TransformLayer::Paint(PaintContext& context) const {
   TRACE_EVENT0("flutter", "TransformLayer::Paint");
   FML_DCHECK(needs_painting());
 
-  SkAutoCanvasRestore save(&context.canvas, true);
-  context.canvas.concat(transform_);
+  SkAutoCanvasRestore save(context.canvas, true);
+  context.canvas->concat(transform_);
   PaintChildren(context);
 }
 

flow/raster_cache.cc

@@ -157,7 +157,7 @@ void RasterCache::Prepare(PrerollContext* context,
                             checkerboard_images_, layer->paint_bounds(),
                             [layer, context](SkCanvas* canvas) {
                               Layer::PaintContext paintContext = {
-                                  *canvas,
+                                  canvas,
                                   nullptr,
                                   context->frame_time,
                                   context->engine_time,

shell/platform/darwin/ios/BUILD.gn

@@ -57,6 +57,8 @@ shared_library("create_flutter_framework_dylib") {
     "framework/Source/FlutterHeadlessDartRunner.mm",
     "framework/Source/FlutterObservatoryPublisher.h",
     "framework/Source/FlutterObservatoryPublisher.mm",
+    "framework/Source/FlutterOverlayView.h",
+    "framework/Source/FlutterOverlayView.mm",
     "framework/Source/FlutterPlatformPlugin.h",
     "framework/Source/FlutterPlatformPlugin.mm",
     "framework/Source/FlutterPlatformViews_Internal.h",

shell/platform/darwin/ios/framework/Source/FlutterOverlayView.h

@@ -0,0 +1,28 @@
+// Copyright 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SHELL_PLATFORM_IOS_FRAMEWORK_SOURCE_FLUTTER_OVERLAY_VIEW_H_
+#define SHELL_PLATFORM_IOS_FRAMEWORK_SOURCE_FLUTTER_OVERLAY_VIEW_H_
+
+#include <UIKit/UIKit.h>
+
+#include <memory>
+
+#import "FlutterPlatformViews_Internal.h"
+
+#include "flutter/fml/memory/weak_ptr.h"
+#include "flutter/shell/common/shell.h"
+#include "flutter/shell/platform/darwin/ios/ios_surface.h"
+
+@interface FlutterOverlayView : UIView
+
+- (instancetype)initWithFrame:(CGRect)frame NS_UNAVAILABLE;
+- (instancetype)initWithCoder:(NSCoder*)aDecoder NS_UNAVAILABLE;
+
+- (instancetype)init NS_DESIGNATED_INITIALIZER;
+- (std::unique_ptr<shell::IOSSurface>)createSurface;
+
+@end
+
+#endif  // SHELL_PLATFORM_IOS_FRAMEWORK_SOURCE_FLUTTER_OVERLAY_VIEW_H_