Merge impeller

.gitignore

@@ -133,6 +133,3 @@ app.*.symbols
 
 # Prebuilt binaries.
 /prebuilts/
-
-# DEPS'd in impeller
-/impeller/

DEPS

@@ -114,9 +114,6 @@ allowed_hosts = [
 deps = {
   'src': 'https://github.com/flutter/buildroot.git' + '@' + '79aa4b0233325e6590dcd45a9af1526d9d2ad13b',
 
-  'src/flutter/impeller':
-   Var('github_git') + '/flutter/impeller' + '@' + '3fc18967345f5e4971259a9efabb11731b751df3',
-
    # Fuchsia compatibility
    #
    # The dependencies in this section should match the layout in the Fuchsia gn

impeller/.clang-format

@@ -0,0 +1,5 @@
+# Defines the Chromium style for automatic reformatting.
+# http://clang.llvm.org/docs/ClangFormatStyleOptions.html
+BasedOnStyle: Chromium
+Standard: c++17
+EmptyLineBeforeAccessModifier: Always

impeller/.clang-tidy

@@ -0,0 +1,24 @@
+---
+Checks:          'clang-diagnostic-*,clang-analyzer-*,google-*,readability-identifier-naming,-google-explicit-constructor,cppcoreguidelines-prefer-member-initializer,modernize-use-default-member-init'
+WarningsAsErrors: ''
+HeaderFilterRegex: ''
+AnalyzeTemporaryDtors: false
+FormatStyle:     none
+CheckOptions:
+  - key:             readability-identifier-naming.PrivateMemberCase
+    value:           'lower_case'
+  - key:             readability-identifier-naming.EnumConstantCase
+    value:           'CamelCase'
+  - key:             readability-identifier-naming.EnumConstantPrefix
+    value:           'k'
+  - key:             readability-identifier-naming.PrivateMemberSuffix
+    value:           '_'
+  - key:             readability-identifier-naming.PublicMethodCase
+    value:           'CamelCase'
+  - key:             readability-identifier-naming.PrivateMethodCase
+    value:           'CamelCase'
+  - key:             cppcoreguidelines-prefer-member-initializer.UseAssignment
+    value:           true
+  - key:             modernize-use-default-member-init.UseAssignment
+    value:           true
+...

impeller/.github/dependabot.yml

@@ -0,0 +1,16 @@
+# See Dependabot documentation for all configuration options:
+# https://help.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    reviewers:
+      - "hixie"
+      - "godofredoc"
+    labels:
+      - "team"
+      - "team: infra"
+      - "waiting for tree to go green"

impeller/.github/workflows/scorecards-analysis.yml

@@ -0,0 +1,53 @@
+name: Scorecards supply-chain security
+on:
+  # Only the default branch is supported.
+  branch_protection_rule:
+  push:
+    branches: [ main ]
+
+# Declare default permissions as read only.
+permissions: read-all
+
+jobs:
+  analysis:
+    name: Scorecards analysis
+    runs-on: ubuntu-latest
+    permissions:
+      # Needed to upload the results to code-scanning dashboard.
+      security-events: write
+      actions: read
+      contents: read
+
+    steps:
+      - name: "Checkout code"
+        uses: actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b
+        with:
+          persist-credentials: false
+
+      - name: "Run analysis"
+        uses: ossf/scorecard-action@c1aec4ac820532bab364f02a81873c555a0ba3a1
+        with:
+          results_file: results.sarif
+          results_format: sarif
+          # Read-only PAT token. To create it,
+          # follow the steps in https://github.com/ossf/scorecard-action#pat-token-creation.
+          repo_token: ${{ secrets.SCORECARD_READ_TOKEN }}
+          # Publish the results to enable scorecard badges. For more details, see
+          # https://github.com/ossf/scorecard-action#publishing-results.
+          # For private repositories, `publish_results` will automatically be set to `false`,
+          # regardless of the value entered here.
+          publish_results: true
+
+      # Upload the results as artifacts (optional).
+      - name: "Upload artifact"
+        uses: actions/upload-artifact@6673cd052c4cd6fcf4b4e6e60ea986c889389535
+        with:
+          name: SARIF file
+          path: results.sarif
+          retention-days: 5
+
+      # Upload the results to GitHub's code scanning dashboard.
+      - name: "Upload to code-scanning"
+        uses: github/codeql-action/upload-sarif@1ed1437484560351c5be56cf73a48a279d116b78
+        with:
+          sarif_file: results.sarif

impeller/.gitignore

@@ -0,0 +1,26 @@
+
+# commonly generated files
+*.pyc
+*~
+.*.sw?
+.ccls-cache
+.checkstyle
+.clangd
+.classpath
+.cproject
+.DS_Store
+.gdb_history
+.gdbinit
+.idea
+.ignore
+.landmines
+.packages
+.project
+.pub
+.pydevproject
+.vscode
+compile_commands.json
+cscope.*
+Session.vim
+tags
+Thumbs.db

impeller/BUILD.gn

@@ -0,0 +1,74 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("tools/impeller.gni")
+
+config("impeller_public_config") {
+  include_dirs = [ ".." ]
+
+  defines = []
+
+  if (impeller_supports_platform) {
+    defines += [ "IMPELLER_SUPPORTS_PLATFORM=1" ]
+  }
+
+  if (impeller_supports_rendering) {
+    defines += [ "IMPELLER_SUPPORTS_RENDERING=1" ]
+  }
+
+  if (is_win) {
+    defines += [
+      "_USE_MATH_DEFINES",
+
+      # TODO(dnfield): https://github.com/flutter/flutter/issues/50053
+      "_SILENCE_CXX17_CODECVT_HEADER_DEPRECATION_WARNING",
+    ]
+  }
+}
+
+group("impeller") {
+  public_deps = [
+    "archivist",
+    "base",
+    "geometry",
+    "tessellator",
+  ]
+
+  if (impeller_supports_rendering) {
+    public_deps += [
+      "aiks",
+      "display_list",
+      "entity",
+      "image",
+      "renderer",
+      "typographer",
+    ]
+  }
+}
+
+executable("impeller_unittests") {
+  testonly = true
+
+  deps = [
+    "archivist:archivist_unittests",
+    "base:base_unittests",
+    "blobcat:blobcat_unittests",
+    "compiler:compiler_unittests",
+    "geometry:geometry_unittests",
+    "tessellator:tessellator_unittests",
+  ]
+
+  if (impeller_supports_rendering) {
+    deps += [
+      "aiks:aiks_unittests",
+      "display_list:display_list_unittests",
+      "entity:entity_unittests",
+      "fixtures",
+      "image:image_unittests",
+      "playground",
+      "renderer:renderer_unittests",
+      "typographer:typographer_unittests",
+    ]
+  }
+}

impeller/README.md

@@ -0,0 +1,151 @@
+```
+--------------------------------------------------------------------------------
+--------------------------------------------------------------------------------
+-----------------   ___                      _ _            --------------------
+-----------------  |_ _|_ __ ___  _ __   ___| | | ___ _ __  --------------------
+-----------------   | || '_ ` _ \| '_ \ / _ \ | |/ _ \ '__| --------------------
+-----------------   | || | | | | | |_) |  __/ | |  __/ |    --------------------
+-----------------  |___|_| |_| |_| .__/ \___|_|_|\___|_|    --------------------
+-----------------                |_|                        --------------------
+--------------------------------------------------------------------------------
+--------------------------------------------------------------------------------
+```
+
+⚠️ Impeller is a Prototype and Work-In-Progress. Proceed with caution. ⚠️
+
+Impeller is a rendering runtime for Flutter with the following objectives:
+
+* **Predictable Performance**: All shader compilation and reflection is
+  performed offline at build time. All pipeline state objects are built upfront.
+  Caching is explicit and under the control of the engine.
+* **Instrumentable**: All graphics resources (textures, buffers, pipeline state
+  objects, etc..) are tagged and labeled. Animations can be captured and
+  persisted to disk without affecting per-frame rendering performance.
+* **Portable**: Not tied to a specific client rendering API. Shaders are
+  authored once and converted as necessary.
+* **Uses Modern Graphics APIs Effectively**: Makes heavy use of (but doesn’t
+  depend on) features available in Modern APIs like Metal and Vulkan.
+* **Makes Effective Use of Concurrency**: Can distribute single-frame workloads
+  across multiple threads if necessary.
+
+## Project Organization
+
+Impeller is a meta-framework. While a user of Impeller may choose to include the
+whole enchilada (in `//impeller/:impeller`), the various sub-frameworks have
+clearly defined responsibilities and adhere to a strict hierarchy.
+
+Impeller itself may not depend on anything in `//flutter` except `//flutter/fml`
+and `flutter/display_list`. FML is a base library for C++ projects and Impeller
+implements the display list dispatcher interface to make it easy for Flutter to
+swap the renderer with Impeller. Impeller is meant to be used by the Flow
+(`//flutter/flow`) subsystem. Hence the name. The tessellator and geometry
+libraries are exceptions - they unconditionally may not depend on anything from
+`//flutter`.
+
+An overview of the major sub-frameworks, their responsibilities, and, relative
+states of completion:
+
+* **`//impeller/compiler`**: The offline shader compiler. Takes GLSL 4.60 shader
+  source code and converts it into a backend specific shader representation
+  (like Metal Shading Language). It also generates C++ bindings that callers can
+  include as a GN `source_set`s so there is no runtime shader reflection either.
+  The target is an executable called `impellerc` which is never shipped into the
+  binary or as an artifact.
+* **`//impeller/renderer`**: The very lowest level of the renderer that is still
+  backend agnostic. Allows users to build a renderer from scratch with few
+  restrictions. Has utilities for creating allocators, generating pipeline state
+  objects from bindings generated by `//impeller/compiler`, setting up render
+  passes, managing jumbo uniform-buffers, tessellators, etc..
+  * **`//impeller/renderer/backend`**: Contains all the implementation details
+      for a specific client rendering API. The interfaces in these targets are
+      meant to be private for non-WSI user targets. No Impeller sub-frameworks
+      may depend on these targets.
+* **`//impeller/archivist`**: Allows persisting objects to disk as performantly
+  as possible (usually on a background thread). The framework is meant to be
+  used for storing frame meta-data and related profiling/instrumentation
+  information. Collection of information should succeed despite process crashes
+  and retrieval of traces must not use inordinate amounts of time or memory
+  (which usually leads to crashes).
+* **`//impeller/geometry`**: All (or, most of) the math! This C++ mathematics
+  library is used extensively by Impeller and its clients. The reasonably
+  interesting bit about this library is that all types can be used
+  interchangeably in device and host memory. Various Impeller subsystems
+  understand these types and can take care of packing and alignment concerns
+  w.r.t these types.
+* **`//impeller/playground`**: When working with graphics APIs, it is often
+  necessary to visually verify rendering results as a specific feature is being
+  worked upon. Moreover, it is useful to attach frame debuggers or profilers to
+  specific test cases. The playground framework provides Google Test fixtures
+  that open the current state of various rendering related objects in a window
+  in which rendering results can be visualized, or, to which frame debuggers can
+  be attached. Most Impeller sub-frameworks that have a test harness also have a
+  custom playground subclass. This sub-framework is only meant to provide
+  utilities for tests and will not be compiled into any shipping binary.
+* **`//impeller/entity`:** Sits one level above `//impeller/renderer` and
+  provides a framework for building 2D renderers. Most of the pipeline state
+  objects generated from shaders authored at build time reside in this
+  framework. The render-pass optimization and pass-rewriting framework also
+  resides there. This allows authoring composable 2D rendering optimizations
+  (like collapsing passes, or, eliding them completely).
+* **`//impeller/aiks`**: Aiks wraps `//impeller/entity` into an API that
+  resembles Skia. This makes it easy to mechanically replace Skia calls with
+  their Impeller counterparts even though the `//impeller/entity` framework API
+  is different from Skia. This presence of this sub-framework is probably
+  short-lived as integration of Impeller into Flutter should likely happen via a
+  custom Display List implementation in `//impeller/display_list`. The
+  roadblocks to this today are graphics package agnosticism in the Display List
+  interface.
+* **`//impeller/display_list`**: The replacement for `//impeller/aiks` to serve
+  in the integration of Impeller in `//flutter/flow`. This is pending graphics
+  package agnosticism in the Impeller interface. This sub-framework primarily
+  provides a custom implementation of the `flutter::DisplayListDispatcher` that
+  forwards Flutter rendering intent to Impeller.
+* **`//impeller/base`**: Contains C++ utilities that are used throughout the
+  Impeller family of frameworks. Ideally, these should go in `//flutter/fml` but
+  their use is probably not widespread enough to at this time.
+* **`//impeller/image`**: The Impeller renderer works with textures whose memory
+  is resident in device memory. However, pending the migration of
+  `//flutter/display_list` to graphics package agnosticism and the subsequent
+  migration of the image decoders to work with the package agnostic types, there
+  needs to be a way for tests and such to decode compressed image data. This
+  sub-framework provides that functionality. This sub-framework is slated for
+  removal and must not be used outside of tests.
+* **`//fixtures`**: Contains test fixtures used by the various test harnesses.
+  This depends on `//flutter/testing`.
+* **`//tools`**: Contains all GN rules and python scripts for working with
+  Impeller. These include GN rules processing GLSL shaders, including reflected
+  shader information as source set targets, and, including compiled shader
+  intermediate representations into the final executable as binary blobs for
+  easier packaging.
+
+## The Offline Shader Compilation Pipeline
+
+* Shaders are authored once in GLSL 4.60. This choice of shading language is
+  consistent across all backends. Shader code resides in the Impeller source
+  tree like any other source file.
+* At build time, the Impeller Shader Compiler (`impellerc`) converts the GLSL
+  into SPIRV. No optimizations are performed on the generated SPIRV at this
+  stage. This is to preserve all debugging and instrumentation information.
+* Using the SPIRV, a backend specific transpiler converts the SPIRV to the
+  appropriate high-level shading language. This is controlled using flags to the
+  `impellerc`.
+* All the files generated in the high-level shading language are compiled,
+  optimized, and linked into a single binary blob.
+* The binary blob containing the compiled and optimized high-level shading
+  language is included as a hex dump (see `xxd.py`) into a C source file with a
+  generated GN target. Executable targets that want to include the compiled code
+  in their binaries just need to depend on the generated GN target. This eases
+  any shader packaging concerns.
+* In parallel, the SPIRV is processed by a reflector. This produces C++
+  translation units that allow for the easy creation of pipeline state objects
+  at runtime. The headers for these translation units include any structs (with
+  appropriate padding and alignment) such that uniform data as well as vertex
+  information can be specified to the shader without having to deal with
+  bindings, vertex descriptors, etc.. This also makes iterating on shaders
+  easier as changes to the shader interface lead to compile time errors.
+* The C++ translation units generated from reflected shader information are made
+  available to callers as a generated GN target that callers may use if
+  necessary. It is possible for callers to perform reflection at runtime but
+  there are no Impeller components that do this currently.
+
+![Shader Compilation Pipeline](docs/shader_pipeline.png)